Can you use batteries that have been in storage for a really long time? Lets find out!

Do Batteries Really Expire?

Do batteries expire? This seems like an obvious question—much more obvious if you ask whether sour cream or milk expires, because you can’t use them after their expiration dates. But batteries are different. You can still use some batteries after they “expire,” yet not all. I’ll get into why.<h2>Alkaline Batteries</h2>Your standard alkaline AA, AAA, C, D and 9 V batteries have a shelf life of about five to ten years, which is really long. But those batteries definitely expire: after so many years, the unavoidable 2–3 % per year self-discharge inevitably leads to a dead alkaline battery. The thing is, you cannot recharge them.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/jpeg&quot;,&quot;filename&quot;:&quot;alk.jpg&quot;,&quot;filesize&quot;:162717,&quot;height&quot;:1200,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/uN0CUEqP8YMiFSBdTId5AQ99p0XfoRWMYsqKJEVx.jpg&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/uN0CUEqP8YMiFSBdTId5AQ99p0XfoRWMYsqKJEVx.jpg&quot;,&quot;width&quot;:1058}" data-trix-content-type="image/jpeg" data-trix-attributes="{&quot;caption&quot;:&quot;Standard Alkaline AA Bateries&quot;,&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--jpg"><a href="https://admin.cellsaviors.com/storage/uN0CUEqP8YMiFSBdTId5AQ99p0XfoRWMYsqKJEVx.jpg"><img src="https://admin.cellsaviors.com/storage/uN0CUEqP8YMiFSBdTId5AQ99p0XfoRWMYsqKJEVx.jpg" width="1058" height="1200"><figcaption class="attachment__caption attachment__caption--edited">Standard Alkaline AA Bateries</figcaption></a></figure>Think about that: you have a battery sitting on the shelf, charged at a certain level, and it’s always going down—2–3 % per year, every year, forever. Technically, it can never reach 0 %, but it will very quickly reach a percentage so low that the voltage is below nominal and won’t power anything you put it in—other than maybe a remote control. Everyone knows that trick:<ol><li>You need a AA for your device, but the batteries are dead.</li><li>You take the “dead” batteries from your remote control and put them in your device.</li><li>You put fresh batteries in the remote, and it’ll last for another year.</li></ol>Other than powering remote controls (which we can all agree isn’t important in an emergency), alkaline batteries are useless after a certain time. But that time span is rather long.<h2>Lithium Primary Batteries</h2>Next on the list are lithium primary batteries. These are like a hybrid between non-rechargeable alkalines and fully rechargeable lithium-ion batteries. They use lithium, so they have a higher voltage and very low self-discharge—about 1 % per year. They’re chemically stable but not rechargeable. Yes, these batteries also “expire” because once their voltage falls too low, you can no longer use them.<h2>Zinc Carbon Batteries</h2>Zinc carbon batteries are still in production today. The only reason they haven’t been replaced by alkaline, lithium-ion, or lead-acid batteries is their stunningly low manufacturing cost. In developing countries—where shipping produced alkaline batteries can be expensive—these can be locally manufactured using simple processes and easily sourced materials. However, they have a very high self-discharge (up to 5 % per year) and are not rechargeable. So these batteries definitely expire.<h2>Lithium-Ion Rechargeable Batteries</h2>This brings us to the most ubiquitous, most popular, most commonly used type of battery: the lithium-ion rechargeable battery. It has the shortest shelf life of all the battery types mentioned—two to three years—due to its 2–5 % self-discharge per month. Unlike other batteries, lithium-ion cells require a Battery Management System (BMS), which is an active electronic device that draws power from the cells it protects.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/jpeg&quot;,&quot;filename&quot;:&quot;lithium.jpg&quot;,&quot;filesize&quot;:10667,&quot;height&quot;:678,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/7wG5qJiP3uL08unuUJYZk0N4uv0ec8cLAWeGWutK.jpg&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/7wG5qJiP3uL08unuUJYZk0N4uv0ec8cLAWeGWutK.jpg&quot;,&quot;width&quot;:1024}" data-trix-content-type="image/jpeg" data-trix-attributes="{&quot;caption&quot;:&quot;An 18650 Lithium Ion battery cell&quot;,&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--jpg"><a href="https://admin.cellsaviors.com/storage/7wG5qJiP3uL08unuUJYZk0N4uv0ec8cLAWeGWutK.jpg"><img src="https://admin.cellsaviors.com/storage/7wG5qJiP3uL08unuUJYZk0N4uv0ec8cLAWeGWutK.jpg" width="1024" height="678"><figcaption class="attachment__caption attachment__caption--edited">An 18650 Lithium Ion battery cell</figcaption></a></figure>Good news: even though lithium-ion batteries self-discharge faster and die on the shelf quicker than other types, you can recharge them. The recharging process itself is almost 100 % efficient (about 99.9 %), with minor losses only if you charge too fast: the cells’ internal resistance produces heat. You’ll also lose energy converting current via a constant-current buck or boost converter, which are 90–95 % efficient. But the key point is—they’re rechargeable.<h2>Preparing for Emergency Power</h2>Ultimately, you need a mixture of two battery types if you’re preparing for a power outage or disaster scenario:<ol><li>Lithium-ion batteries—because they’re rechargeable. Even if there’s no grid power, you can use solar panels or a generator (on fuel or vegetable oil) to produce energy and then store it.</li><li>Alkaline batteries—because, if fully charged and shelved for years, they still retain most of their charge due to low self-discharge. In six years, they might still be at ~80 % charge, ready when you need them.</li></ol>When you go to use lithium-ion batteries after years on the shelf, they’ll be dead—you’ll need to recharge them first. And that takes time and infrastructure. Alkalines, on the other hand, deliver immediate power (until they hit end-of-life).<h2>Can You Use 10 Year Old Batteries?</h2>Yes, but with some caveats. In 10 years, AA, AAA, C, and D alkaline cells will have lost around half of their capacity, and the voltage will seriously sag under load, but they will probably work. Primary lithium cells like CR2032 will be able to retain most of their charge and maintain a relatively steady voltage after a decade, so they’ll usually still work in things like CMOS backup or calculators (though it’s wise to check their voltage), but dont expect them to work for long at that point. Rechargeable lithium-ion packs, however, age out in 3–5 years; at ten years they’ve lost most capacity and a lot of their current carrying capability, but they will still work for low current applications or in a massively parallel configuration.&nbsp;<h2>Battery “End of Life”</h2>Eventually, even rechargeable cells break down, regardless of cycle count. But it takes a very long time. And even at “end of life” (when they can only store ~80 % of original capacity), lithium-ion batteries are still useful. Their voltage may drop more under load, but most devices include voltage regulators, so they keep working.So yes—lithium-ion batteries can expire, but “expiration” simply means you no longer get the manufacturer-rated capacity. They’ll probably keep working beyond that point.

Do Batteries Expire?

Lets explore the ins and outs of constant voltage regulators. 

What Exactly Is A Voltage Regulator?

&nbsp;A voltage regulator is a device that stabilizes a system’s voltage under varying load conditions. For example, the DC output from an alternator can fluctuate between 13 V and 15 V, but to charge a car battery you need a steady voltage. The regulator—either built into the alternator or installed separately—ensures that the battery sees a constant charging voltage.Similarly, when converting AC to DC, you typically use a transformer to step the AC voltage down, then a bridge rectifier to produce DC. That raw DC is often very “choppy,” and while capacitors help smooth it out, sensitive electronics generally require a more precise regulation stage.Voltage regulators are also used not merely to clean up a noisy supply but to convert one voltage level to another. The most common use is stepping down a higher voltage to a lower one suitable for loads.<h2>Linear vs. Switch-Mode Regulators</h2><figure data-trix-attachment="{&quot;contentType&quot;:&quot;image&quot;,&quot;height&quot;:556,&quot;url&quot;:&quot;https://grangeramp.com/wp-content/uploads/2015/03/products-7812.jpg&quot;,&quot;width&quot;:451}" data-trix-content-type="image" data-trix-attributes="{&quot;caption&quot;:&quot;Linear Voltage Regulator&quot;}" class="attachment attachment--preview"><img src="https://grangeramp.com/wp-content/uploads/2015/03/products-7812.jpg" width="451" height="556"><figcaption class="attachment__caption attachment__caption--edited">Linear Voltage Regulator</figcaption></figure>&nbsp;Voltage regulators fall into two main categories: linear regulators and switch-mode converters (buck for step-down, boost for step-up). Linear regulators work by dissipating the excess voltage as heat. If the voltage drop is large and the current significant, the regulator can overheat—even with hefty heat sinks and fans—because the package itself can’t shed enough power.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image&quot;,&quot;height&quot;:835,&quot;url&quot;:&quot;https://a.pololu-files.com/picture/0J5851.1200.jpg?d7ecfd2d1dd922f537ce44c02e13305b&quot;,&quot;width&quot;:1200}" data-trix-content-type="image" data-trix-attributes="{&quot;caption&quot;:&quot;Small switch mode voltage regulator&quot;}" class="attachment attachment--preview"><img src="https://a.pololu-files.com/picture/0J5851.1200.jpg?d7ecfd2d1dd922f537ce44c02e13305b" width="1200" height="835"><figcaption class="attachment__caption attachment__caption--edited">Small switch mode voltage regulator</figcaption></figure>By contrast, switch-mode regulators rapidly switch their pass element on and off, controlling the duty cycle to maintain a steady output. This approach can reach efficiencies of up to 95 %, allowing both step-down and step-up operation with minimal heat generation. For example, a switch-mode converter can take a 24 V supply and efficiently produce 12 V at several amps, provided the module supports the required current.<h2>LM2596 DC-to-DC Buck Converter Modules</h2>&nbsp;One of the most ubiquitous low-cost switch-mode regulators is based on the LM2596 chip. These DC-to-DC buck modules are often sold in multi-packs—for instance, seven modules for around $13 with free shipping. Each typically supports up to 35 V input and advertises a 1.25 V–30 V adjustable output at 3 A.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:907700,&quot;height&quot;:912,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/cNdOnpcfRsGsJZpWCKOBG6vViyit9g2b9XtLhuiL.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/cNdOnpcfRsGsJZpWCKOBG6vViyit9g2b9XtLhuiL.png&quot;,&quot;width&quot;:1200}" data-trix-content-type="image/png" data-trix-attributes="{&quot;caption&quot;:&quot;Mini LM2596 Buck Converter&quot;,&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/cNdOnpcfRsGsJZpWCKOBG6vViyit9g2b9XtLhuiL.png"><img src="https://admin.cellsaviors.com/storage/cNdOnpcfRsGsJZpWCKOBG6vViyit9g2b9XtLhuiL.png" width="1200" height="912"><figcaption class="attachment__caption attachment__caption--edited">Mini LM2596 Buck Converter</figcaption></a></figure>In practice, however, you won’t reliably draw 3 A continuously without additional cooling. At currents above 1.5 A they tend to get quite hot, and you’d need a good copper heat sink, thermal compound, and possibly a fan. With minimal heatsinking you can expect about 1–1.5 A continuous, or brief peaks of 3–4 A for a second or two. These modules work well to power small loads—such as LED strips—where about 10 W of output (at 12 V × 0.8 A) is sufficient. <h2>LM2596S Modules with Display</h2> &nbsp;A variation on the classic LM2596 module adds an integrated digital display so you can monitor the output voltage in real time. While a pack of two such boards cost around $8, the larger PCB area helps dissipate heat more effectively, giving roughly 10–20 % higher current capacity without extra cooling. Pick up your <a href="https://www.amazon.com/Converter-Step-Down-Regulator-Voltmeter-Compatible/dp/B089KBS5XR/&amp;tag=cellsavior08-20">Voltage Regulator with Display </a>today on Amazon.&nbsp;<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:1988546,&quot;height&quot;:1180,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/qc8QeOlPJQ8t1ioxnRQhIu3jufSvtDn2ZDJkdU0i.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/qc8QeOlPJQ8t1ioxnRQhIu3jufSvtDn2ZDJkdU0i.png&quot;,&quot;width&quot;:1492}" data-trix-content-type="image/png" data-trix-attributes="{&quot;caption&quot;:&quot;LM2596S Module With Display&quot;,&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/qc8QeOlPJQ8t1ioxnRQhIu3jufSvtDn2ZDJkdU0i.png"><img src="https://admin.cellsaviors.com/storage/qc8QeOlPJQ8t1ioxnRQhIu3jufSvtDn2ZDJkdU0i.png" width="1492" height="1180"><figcaption class="attachment__caption attachment__caption--edited">LM2596S Module With Display</figcaption></a></figure>The display makes voltage trimming more convenient, but if you don’t need to read back voltage and want the smallest, cheapest solution, the plain modules remain appealing.<h2>20 A / 300 W Constant-Current Buck Converter</h2>&nbsp;Although marketed as a constant-current module, setting the current knob fully clockwise converts it into a robust constant-voltage regulator. These boards include heat sinks on the power stages and handle 6 V–40 V inputs. You can draw 10 A continuously (with a fan), and up to 16–17 A near their limits. True 20 A output requires replacing the thermal film with quality paste, larger heat sinks, and active cooling.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image&quot;,&quot;height&quot;:1492,&quot;url&quot;:&quot;https://m.media-amazon.com/images/I/718AzM4bXsL._AC_SL1500_.jpg&quot;,&quot;width&quot;:1500}" data-trix-content-type="image" data-trix-attributes="{&quot;caption&quot;:&quot;\&quot;20A\&quot; Constant Current Buck Converter&quot;}" class="attachment attachment--preview"><img src="https://m.media-amazon.com/images/I/718AzM4bXsL._AC_SL1500_.jpg" width="1500" height="1492"><figcaption class="attachment__caption attachment__caption--edited">"20A" Constant Current Buck Converter</figcaption></figure>With proper cooling, you can power several hundred watts of DC equipment: from 12 V inverters to laptop DC-barrel devices. For instance, you could buck a 4 S Li-ion battery down to 13–14 V to drive a small pure-sine inverter, or drop 24 V to around 19.5 V to run a laptop directly, bypassing its internal AC-DC stage. You can get this awesome <a href="https://www.amazon.com/WWZMDiB-Converter-Adjustable-Regulator-Protection/dp/B0B825HRB9/&amp;tag=cellsavior08-20">constant current buck converter </a>on Amazon.<h2>USB Charge Modules&nbsp; 5 V Regulators</h2>These small red USB charge boards may look like simple phone chargers, but electrically they’re just 5 V switch-mode regulators. These typically support up to 3 A output (practically 2.4–2.8 A with a good cable) from inputs up to 24 V. They don’t implement USB PD or Quick Charge protocols, but they’re ideal for powering ESP32s, Arduinos, fans, or even charging phones at the baseline 15 W USB-PD rate.You can buy five of these modules for under $10, making them cost-effective to stock for any project requiring a basic 5 V supply. Their simplicity and low price mean you can solder one in wherever you need a USB power port. Pickup your <a href="https://www.amazon.com/HiLetgo-DC-DC-Module-Charger-Arduino/dp/B01HXU1C6U/&amp;tag=cellsavior08-20">5 pack of USB charge modules </a>on Amazon today!<h2>Conclusion</h2>Voltage regulators come in all shapes and sizes: the LM2596 DC-DC buck modules offer adjustable 1.25 V–30 V outputs at around 1–1.5 A for small loads; the LM2596S variants with digital displays add real-time voltage readout and larger PCBs for 10–20 % more continuous current without extra cooling; the beefy 20 A/300 W constant-current buck converter doubles as a high-power constant-voltage supply—10 A continuous (up to 16–17 A peaks) with proper heatsinking; and the compact 5 V USB charge modules deliver a baseline 15 W (≈2.5 A) from inputs up to 24 V, making them perfect—and practically disposable—for any USB-powered project.We hope this article helped you learn everything you needed to know about voltage regulators, thanks for reading!

What Is A Voltage Regulator?

Explore the top USB PD modules for every need: compact 65W board, 18W battery bank charger, and 100W high-power bidirectional USB PD module

Best USB PD Modules: Compact, Low, and High Power Picks

USB PD a.k.a USB Power Delivery is extremely versatile. It's used to charge phones, run laptops, power soldering irons, turn motors, and spin fans. Because of this level of flexibility, there's not one single 'best' USB PD module that covers every application perfectly. Instead, we can break choices down into three main categories:<ol><li>Best Bang for the Buck (Cheap/Small Module)</li><li>Best Low Power Battery Bank Module</li><li>Best High Power Battery Bank Module</li></ol>This way, we can cover all the bases so you can find the best USB PD module for your specific application.&nbsp;<h2>Best Bang for the Buck: Tiny USB PD Module</h2><h3>Module Overview</h3>These compact boards are barely wider or longer than a USB A port, yet they support almost the entire USB PD specification: 5 V, 9 V, 12 V, and 20 V at up to 3 A each. They also support PPS (Programmable Power Supply), though few devices currently use this feature. Efficiency ranges from 92 % to 97 %, and the module handles USB PD negotiation on both the input and output sides.<h3>Voltage Input and Output</h3>The module accepts a DC input up to 35 V. Your maximum selectable output voltage depends on the input:<ul><li>12V in → outputs 5V or 9V</li><li>21V in → outputs 5V, 9V, 12V, and 20V</li><li>8.4V in → outputs only 5V</li><li>16.8V in → outputs 5V, 9V, and 12V</li><li>18.1V in → outputs 5V, 9V, and 12V</li></ul>In general, you must supply slightly more voltage than the highest output you need. If you use this module to drive a USB PD trigger board, it handles all voltage selection automatically.<h3>Performance and Protection</h3><ul><li>Power: Capable of 65 W output (3 A × 20 V), though it runs hot at maximum load. Consider a small heatsink or fan for continuous high-current use.</li><li>Safety: Built-in over-temperature, over-current, and short-circuit protection. However, it lacks reverse-polarity detection—connecting input backward will damage the module.</li><li>Quiescent Current: ~3 mA when idle.</li><li>Output Ripple: ~200 mV, which is acceptable for devices with internal regulators (e.g., battery chargers). For sensitive lab experiments, extra filtering may be needed.</li></ul><h3>Mechanical Integration</h3>You can solder a male XT60 connector directly to the board—no wires required—for a compact, low-current connection (few amps). Wrap with 2:1 or 3:1 heat shrink for a neat finish.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image&quot;,&quot;height&quot;:1452,&quot;url&quot;:&quot;https://m.media-amazon.com/images/I/71uPwiPhNyL._AC_SL1500_.jpg&quot;,&quot;width&quot;:1500}" data-trix-content-type="image" class="attachment attachment--preview"><img src="https://m.media-amazon.com/images/I/71uPwiPhNyL._AC_SL1500_.jpg" width="1500" height="1452"><figcaption class="attachment__caption"></figcaption></figure>While some listings claim a 30 V input limit, the module uses 35 V-rated capacitors. In practice, inputs of 32–33 V pose no issues, though we typically operate them between 24 V and 29 V for reliability. It's literally insane that you can get <a href="https://www.amazon.com/Charging-Module-Interface-Supports-Charger/dp/B0DMSXXR9Q/&amp;tag=cellsavior08-20">5 of these modules for 11 dollars on Amazon.</a> Honestly, out of all 4 modules that we are going to cover in the article, this is my favorite one. Its definitely the one that I use the most.&nbsp;<h2>Best USB PD Battery Bank Module (Low Power)</h2>This IP5328P board is, hands down, the best low power battery bank module you can get. It supports 18 W fast charging and has 3 ports, one of which is a bidirectional C port that can be used to either power a USB C device or charge the battery bank itself.<h3>Mechanical Design &amp; Form Factor</h3><figure data-trix-attachment="{&quot;contentType&quot;:&quot;image&quot;,&quot;height&quot;:1050,&quot;url&quot;:&quot;https://m.media-amazon.com/images/I/61vWEIcRUkL._SL1050_.jpg&quot;,&quot;width&quot;:1050}" data-trix-content-type="image" class="attachment attachment--preview"><img src="https://m.media-amazon.com/images/I/61vWEIcRUkL._SL1050_.jpg" width="1050" height="1050"><figcaption class="attachment__caption"></figcaption></figure>It’s the perfect width for an 18650 battery bank with no overhang and sits nicely centered on a 21700-based frame with minimal “bezel.” That makes it easy to fit this thing into compact designs without adding unnecessary bulk to the battery pack.<h3>Input Voltage &amp; Boost Conversion</h3>The best part about this USB PD module is its staggeringly low input voltage requirement. This thing can take a 3 V to 4.2 V input and step it up to either 5 V, 9 V, or 12 V, depending on what the device you plug into it needs.<h3>Output Current Specifications</h3><ul><li>5 V output: up to 3.1 A</li><li>7 V output: up to 2.4 A</li><li>9 V output: up to 2.0 A</li><li>12 V output: up to 1.5 A</li></ul><h3>Safety &amp; Thermal Management</h3>The controller on the board supports over-current, short-circuit, over-voltage, and over-temperature protection. In fact, it actively scales back its boost-stage current as its internal temperature rises, ensuring the die never exceeds its specified thermal limits.<h3>Thermal Behavior &amp; Operational Notes</h3>This is both a good thing and a bad thing. It means that it won’t ever burn up, but it also means that if you run this thing at peak output for extended periods of time, the output voltage could lower to the next lowest level to keep the heat down. Most of the time, you won’t even notice this, but if you are using a USB PD trigger to get a 12 V output out of this board and use that to power a 15 W or more load, after some time it will drop to 9 V unless you supply some cooling.But to be totally honest, that’s not even worth mentioning. Under normal operation, you won’t have the slightest bit of trouble out of this board. It’s only if you are using external equipment (a USB PD trigger) to squeeze the absolute maximum power out of this board that you’ll see any kind of problem— and even in that case, it scales down accordingly. This fantastic <a href="https://www.amazon.com/HiLetgo-IP5328P-Battery-Bi-Directional-Charging/dp/B0CDWWYQTC/&amp;tag=cellsavior08-20">USB PD Battery Bank Module</a> can be purchased on Amazon for the amazingly low price of $13 for two.&nbsp;<h2>Best USB PD Battery Bank Module (High Power)</h2>This high‑power USB Power Delivery (USB‑PD) battery‑bank board uses the IP2368 chipset and delivers up to 100 W of fast charging in both directions. Unlike 1 S‑only modules, it can work with 2 S, 3 S, 4 S, 5 S, or 6 S packs.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image&quot;,&quot;height&quot;:1051,&quot;url&quot;:&quot;https://m.media-amazon.com/images/I/71lKSqhzowL._AC_SL1500_.jpg&quot;,&quot;width&quot;:1500}" data-trix-content-type="image" class="attachment attachment--preview"><img src="https://m.media-amazon.com/images/I/71lKSqhzowL._AC_SL1500_.jpg" width="1500" height="1051"><figcaption class="attachment__caption"></figcaption></figure><h3>2. Default Configuration &amp; BMS</h3>The board leaves the factory set for 4 S operation. Although you will notice several extra connections on the PCB, there is no built‑in BMS — you must add one that matches the cell count. Changing a few resistors lets you switch the board to 2 S, 3 S, 5 S, or 6 S.<h3>3. Bidirectional Boost‑Buck Conversion</h3>The IP2368 is a bidirectional boost‑buck controller:<ul><li>Charging: A 5 V USB input is boosted to the correct voltage to charge, for example, a 4 S pack (up to 16.8 V).</li><li>Discharging: The same circuitry bucks or boosts the battery voltage to any supported USB‑PD rail.</li></ul><h3>Supported USB‑PD Voltages</h3>No matter where the battery sits — around 12 V when low to 16 V when full for a 4 S pack — the board can always output 5 V, 9 V, 12 V, 15 V, or 20 V.&nbsp;<h3>Thermal Performance</h3>A lot of power can flow through this board, and the chips get super‑hot when pushed:<ul><li>Discharge: Typical loads (phones, tablets, USB soldering irons) draw 20–60 W intermittently, so temperatures stay modest.</li><li>Charge: Continuous fast charging can drive the ICs to ~85 °C in open air. Adding a heat‑sink is highly recommended.</li></ul>Configuring the board for 5 S or 6 S reduces current for the same wattage, so it runs cooler. I usually reconfigure these boards for 6 S and pair them with a 6 S BMS. You get the same power with lower current and less heat.&nbsp; These boards are very, very good — despite their excruciatingly hot operation under full load, I have yet to see one fail. But they do run very, VERY hot. Honestly, the best thing to do would be to wire up a tiny 24V to the&nbsp; + on the PCB.&nbsp;<h3>Extra Pads on the PCB</h3>Those extra pads are not for BMS wiring. One pad, marked with a plus sign (+), mirrors whatever USB‑PD mode is active: it shows 5 V until a device negotiates 9 V, 12 V, 15 V, or 20 V, and then the pad follows that voltage. You could attach a small meter here to verify the current PD profile — pretty cool! This thing runs hot, so why not attach a super low power 24V fan to that pin? When operating in 20V mode, it will spin slower than it was rated for, but still fast enough to effectively cool. That will also be true at 15V and 12V. By the time when get to a voltage that the fun will either run very slowly or not at all, we've *also* reached a voltage that simply won't let us output all that much power, rendering the situation unable to get so hot in the first place.&nbsp;Overall, this is the <a href="https://www.amazon.com/Teyleten-Robot-Bidirectional-Buck-Boost-High-Power/dp/B0B7RT7CF4/&amp;tag=cellsavior08-20">best high power USB PD battery bank board</a> you can get on Amazon right now.&nbsp;<h2>A Note About The Listings</h2>As you can see below, there are a lot of errors in these Amazon listings. Its a pretty common problem and is a combination of lack of technical expertise on the part of the listers and poorly translated Chinese.&nbsp;<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:742165,&quot;height&quot;:1108,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/BUIfORTfvxT2z3bqAxAoiyZXvU8hb86vOIGdc7Fd.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/BUIfORTfvxT2z3bqAxAoiyZXvU8hb86vOIGdc7Fd.png&quot;,&quot;width&quot;:2019}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/BUIfORTfvxT2z3bqAxAoiyZXvU8hb86vOIGdc7Fd.png"><img src="https://admin.cellsaviors.com/storage/BUIfORTfvxT2z3bqAxAoiyZXvU8hb86vOIGdc7Fd.png" width="2019" height="1108"><figcaption class="attachment__caption">image.png 724.77 KB</figcaption></a></figure>We end up in a situation where the listings themselves are rather confusing. I have no idea what 'reach' means in context of 'Specification Met' but that is mostly a benign one, as most people would chock that up to a poor translation. But the one above that is more serious. 17 volts DC? Why would that even be there. Its a battery interface on one side, and a USB PD module on the other. Neither of those sides use 17 volts as any of the voltages for any of the standards that they support.&nbsp;So, if you aren't familiar with USB PD, it can be really confusing, and you may end up buying something that cannot at all do what you need it do to do. &nbsp;<h2>So, What's The Best USB PD Module?&nbsp;</h2> If you need an ultra-compact, cost-effective USB-PD module for up to 65 W output with full PD negotiation and PPS support, the tiny 65W PD module is hard to beat; It can run on just about any low voltage battery, but it can't charge the battery that its running on. For that, you would need a USB Power Bank PD module. For low-power applications, the IP5328P module offers 18 W bidirectional charging and robust protection in a perfect form factor; and for high-power (up to 100 W both ways) multi-cell packs (2 S–6 S), the IP2368-based board provides seamless boost-buck operation across all standard PD voltages.We hope this articled helped you learn everything you wanted to know about USB PD Modules. Thanks for reading!

The Best USB PD Module

Learn how long lithium-ion batteries last, including NMC vs LFP cycles, temperature effects, EV tips, and how to extend battery life for years

How Long Do Lithium Ion Batteries Last? Full Guide

How Long Does A Lithium Ion Battery Last

Discover how LFP batteries became the top EV choice—safer, longer-lasting, and now just $115/kWh. Explore their evolution, innovations, and global impact.

The Rise of LFP Batteries: History, Cost & EV Dominance

LFP batteries have become the dominant battery in global EV production and have recently sharply fallen in price to a stunningly low $115/kwh.&nbsp;<h2>What Makes A Given Battery A Given Chemistry?</h2>Like other batteries, lithium-ion batteries have two electrodes, a cathode and an anode. The anode, which is the positive end in these batteries, is generally just graphite—nothing too special there. The cathode is where all the magic happens: that’s where the chemistry lives. It’s also the most expensive part of the battery, making up about 70% of the total value, and it’s the main distinguishing factor between different types of batteries.Two Main Categories: Ternary vs. LFPThere are two main categories of lithium-ion batteries: ternary batteries (made of three elements) and LFP batteries. Ternary batteries mix three different chemicals—either nickel, manganese, cobalt (NMC) or nickel, cobalt, aluminum (NCA)—in varying ratios. These batteries offer the highest energy density but use rare materials, making them more expensive. They’re also sourced from geopolitically tense regions and, due to their high energy density, have a greater risk of thermal runaway.LFP batteries use two different chemicals on the cathode—iron and phosphorus.&nbsp; There’s no nickel or cobalt, and iron and phosphorus are far more common worldwide. This makes LFP batteries much cheaper to produce and gives them a major advantage in cycle life: while NMC batteries retain about 80% of their capacity after 500–800 cycles, LFP batteries can exceed 2,000 cycles without significant degradation. If you’re looking to squeeze even more longevity out of your cells, check out our guide on <a href="https://cellsaviors.com/blog/get-more-cycles-from-lithium-ion-cells">How To Get More Cycles Out Of Lithium Ion Cells</a>.&nbsp;<h2>What Is The Downside Of An LFP Battery?</h2>&nbsp;The big drawback of LFP batteries is their lower energy density—around 90–150 Wh/kg compared to 260–300 Wh/kg for NMC and NCA. Two same-sized batteries, one LFP and one ternary, will store more energy if they use ternary chemistry. However, innovations in LFP chemistry, cell design, and pack integration have begun to narrow this gap. For a side-by-side comparison of these chemistries, see our full breakdown in <a href="https://cellsaviors.com/blog/lifepo4-nmc-chemistry-comparison">NMC&nbsp;Vs. LifePO4 Which Is Best</a>. It’s also important to remember that each chemistry (NMC, NCA, LTO, LFP) has many variations, and pack-level choices can significantly affect performance.&nbsp;<h2>Who Invented LFP Batteries?&nbsp;</h2>John B. Goodenough—yes, that’s his real name—first proposed and patented iron phosphate as a lithium-ion cathode material in the mid-1980s. His LFP chemistry promised better safety and cycle life but suffered from low electrical conductivity and poor energy density (around 90 Wh/kg), limiting its early appeal for electric vehicles.<h2>Why Are LFP Batteries So Cheap Now?</h2>The remarkable affordability of LFP batteries today is the result of many years of advances in materials science, strategic patent licensing and consolidation, and targeted policy incentives that drove early large‐scale adoption. By pooling and licensing key conductivity-enhancing patents, deploying subsidies to jump-start fleet electrification, and then allowing market forces to favor LFP’s inherent safety and longevity as subsidy support for higher-density chemistries waned, manufacturers achieved the economies of scale necessary to push prices sharply downward.Conductivity Boosts and Patent PoolsIn the 2000s, Canadian and European companies formed institutions to develop carbon-coating processes and related patents to enhance LFP conductivity. These patents were consolidated into a Swiss licensing consortium. In the 2010s, Chinese battery firms secured royalty-free domestic rights to these key LFP patents, whereas others worldwide had to pay licensing fees. Initially, Chinese firms could only use these patents domestically. China’s TVTC Policy and Early Adoption In 2009, China launched the TVTC policy (Thousands of Vehicles, Tens of Cities), a subsidy program encouraging local governments to deploy buses, taxis, and government vehicles equipped with LFP batteries. BYD then introduced LFP packs in its eBus and early hybrids, establishing domestic leadership. Outside China, most OEMs still preferred NMC or NCA for their higher energy density. Shifting Subsidies and Market Share Between 2016 and 2019, China shifted subsidies to favor EVs based on performance metrics (charge rate, range), prompting OEMs to chase higher-energy-density ternary chemistries. LFP’s share of new installations in China dropped from about 70% to 30% by mid-2019. Then, mid-2019, China halved its cash subsidies and continued annual cuts, narrowing the cost gap between ternary and LFP batteries. With subsidies rolling back, market forces favored LFP for its safety, cycle life, and lower cost—provided sufficient pack volume could compensate for lower energy density.<h2>Blade Cells and Cell-to-Pack Innovation</h2>In March 2020, BYD unveiled its Blade cells: ultra-thin prismatic LFP modules that eliminate intermediate modules in pack assembly. Traditional EV packs require cells → modules → packs; skipping the module step increases energy density at the pack level. BYD’s Blade-equipped Han EV achieves a 605 km range—about 85% of NMC density—while offering lower cost, better cycle life, and improved safety. Other Chinese OEMs swiftly adopted cell-to-pack (CTP) LFP technology, and by 2021 LFP pack volumes in China overtook NMC. By 2023, LFP accounted for 70% of EV installations in China.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:1466471,&quot;height&quot;:1080,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/tau610n5FSkNiyI6qwh9zZQe6CaZLfE3opwqh4hT.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/tau610n5FSkNiyI6qwh9zZQe6CaZLfE3opwqh4hT.png&quot;,&quot;width&quot;:1920}" data-trix-content-type="image/png" data-trix-attributes="{&quot;caption&quot;:&quot;BYD Blade Cells&quot;,&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/tau610n5FSkNiyI6qwh9zZQe6CaZLfE3opwqh4hT.png"><img src="https://admin.cellsaviors.com/storage/tau610n5FSkNiyI6qwh9zZQe6CaZLfE3opwqh4hT.png" width="1920" height="1080"><figcaption class="attachment__caption attachment__caption--edited">BYD Blade Cells</figcaption></a></figure><h2>Patent Expiry, Raw Materials, and Price Declines</h2>By 2022, core LFP patents began to expire, but China’s industrial base and supply-chain expertise were already dominant. New lithium sources in Australia, Chile, and Argentina came online, and by 2024 iron-ore prices fell ~15% due to a Chinese steel slowdown. LFP pack prices dropped another 20% to around US $115/kWh—making Chinese LFP packs the cheapest globally, even after import tariffs of 25–120%. In 2021, BYD began selling Blade batteries to Toyota, Ford, and others, sparking a price war among battery suppliers.<h2>Stationary Storage and Emerging Chemistries</h2>LFP’s cost and safety advantages have fueled a boom in grid-scale and home energy storage. Its lower energy density matters less for stationary applications. Innovations continue: adding manganese to create LMFP (a ternary lithium-iron-based cathode) boosts energy density, and novel two-step firing processes improve particle uniformity and conductivity.<h2>Conclusion</h2>LFP cell costs are destined to continue declining, and energy density gains may soon challenge NMC’s dominance. What began as an American-engineered, safe but low-energy chemistry has—through Chinese licensing, policy, and technological innovation—become one of the world’s lowest-cost and most promising lithium-ion battery technologies. We hope this article helped you learn more about LFP chemistry and lithium ion batteries in general. Thanks for reading!

A Brief History Of LFP Batteries

Explore modern battery types including alkaline, lithium, NiMH, lead-acid, and more. Compare primary vs. secondary batteries with real-world use cases.

Types of Batteries Today: Primary vs. Rechargeable

<h2>Battery Categories</h2>You can put any given battery in one of two categories. It’s either a primary battery or a secondary battery. A primary battery is a disposable or non‑rechargeable battery, while a secondary battery is a reusable or rechargeable battery. At first glance, you might think a primary battery is a rechargeable battery, but that’s just because we are from this era where rechargeable batteries have finally become good enough to be the most common kind of battery for many applications, so it just seems like they should be the 'primary' ones.<h2>Primary Batteries</h2>When it comes to primary batteries, we still use alkaline, zinc carbon, and lithium non‑rechargeable batteries. Pretty much all the other chemistries have gone by the historical wayside. Alkaline is the most popular type of primary battery, while zinc batteries are still used in developing parts of the world due to their extremely low cost.&nbsp;<h3>Alkaline</h3>Alkaline is still widely used in household devices like remote controls and flashlights. It’s extremely low‑cost. It has a very long shelf life. They can last up to 10 years, and they have a relatively stable voltage under load. They’re obviously non‑rechargeable, so you pay for them once and use them once rather than paying for them once and using them over and over again.<h3>Zinc Carbon</h3>In some parts of the world and in some niche applications, zinc carbon batteries are still used. It’s an older technology, and it’s generally only found in low‑drain devices. It’s extremely cheap to manufacture, which is pretty much the only reason it’s still used, but they have a very low capacity and their voltage drops pretty tremendously under even moderate loads, and they have a shorter shelf life.<h3>Lithium (Non‑Rechargeable)</h3>Another type of primary battery that’s become increasingly popular lately are lithium batteries. Usually we associate lithium batteries as being rechargeable, but in this case they aren’t. They are used in high‑drain or extreme‑temperature applications like in cameras, sensors, etc. They have extremely high energy density, a very long 10‑plus‑year shelf life, and a wide operating‑temperature range; but they are more expensive, and they have some safety considerations, as you’d expect with any other lithium‑ion battery technology, because they have such a low resistance that they can deliver a tremendous amount of current under short‑circuit situations.<h2>Secondary Batteries</h2>Now we’ve come to the secondary batteries, which are also known as rechargeable batteries.<h3>Lead Acid</h3>&nbsp;We still use lead-acid batteries in many applications. They’re still dominant in the automotive industry and they’re used as starter batteries. They’re still used as backup batteries in small-scale UPSs, which are uninterruptible power supplies, and some people still use them for off-grid solar, although you can make a pretty clear point that the total cost of ownership is actually higher with lead-acid batteries in that regard. Lead acid batteries have a very low cost per kilowatt-hour and they are extremely reliable. If you’re considering a retrofit, check out our guide on <a href="https://cellsaviors.com/blog/lead-acid-agm-lithium-replacement">How To Replace Lead Acid/AGM With Lithium </a>to see the potential benefits and pitfalls of moving to a lithium-based system. &nbsp;Lead-acid batteries are extremely heavy, very low-energy-density, and contain large amounts of lead that have to be contended with one way or the other.&nbsp;<h3>Nickel Cadmium</h3>Nickel‑cadmium batteries are still in use in some very old devices. There’s plenty of drills and things out there that were designed to run on nickel‑cadmium batteries, and they’re still working. They can tolerate extreme temperatures, and they have very high discharge rates. A major con of NiCd is the memory effect, and cadmium is very toxic; they’ve largely been phased out by nickel‑metal‑hydride.<h3>Nickel Metal Hydride</h3>Nickel‑metal‑hydride technology is still used in rechargeable AAs and AAAs and in some hybrid vehicles like the older Toyota Prius. NiMh batteries have a higher capacity compared to NiCd and less of a memory effect, but they still have a memory effect. They have a relatively high self‑discharge rate compared to other battery technologies and only a moderate energy density.<h2>Lithium‑Ion Rechargeable Batteries</h2>&nbsp;And now, of course, that brings us to the most popular type of battery of all time: the lithium-ion rechargeable battery. This thing is ubiquitous in consumer electronics such as smartphones, laptops, electric vehicles, and more. And you can even find it in industrial applications like grid-storage systems. There are many types of lithium-ion chemistries, but the three most popular are LCO, NMC, and LFP. If you’re looking to build your own pack from scratch, take a look at our step-by-step walkthrough in <a href="https://cellsaviors.com/blog/building-a-battery-pack-from-18650-cells">Building A Lithium Battery Pack From 18650 Cells</a>.&nbsp;There are many types of lithium‑ion chemistries, but the three most popular are:<ul><li>LCO (lithium cobalt oxide): Known for its extremely high energy density, and it’s used most of the time in phones and laptops. </li><li>NMC (lithium nickel manganese cobalt oxide): A close relative of LCO, it offers the best balance of energy, power, and longevity, and it’s mainly used in electric vehicles, phones, drills, RC applications, and more. </li><li>LFP (lithium iron phosphate): An up‑and‑coming chemistry with a much longer cycle life than the other two lithium‑ion chemistries; it’s much safer, and it finds the best use in stationary storage applications and some EVs that have the space and are efficient enough to not need a lot of capacity.</li><li><figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:1170178,&quot;height&quot;:1024,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/cPljHUrCz9tdbskdqVBdlOlHk8Rz0TTgGiUmG9Ym.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/cPljHUrCz9tdbskdqVBdlOlHk8Rz0TTgGiUmG9Ym.png&quot;,&quot;width&quot;:1024}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/cPljHUrCz9tdbskdqVBdlOlHk8Rz0TTgGiUmG9Ym.png"><img src="https://admin.cellsaviors.com/storage/cPljHUrCz9tdbskdqVBdlOlHk8Rz0TTgGiUmG9Ym.png" width="1024" height="1024"><figcaption class="attachment__caption">image.png 1.12 MB</figcaption></a></figure></li></ul><h2>Why are batteries called AA, AAA, C, and D?</h2>At first, the battery names only went up in size. With A being the smallest battery, B being a little larger, and C even larger than that, and so on. But as technology progressed and devices and the batteries powering them actually ended up getting smaller, the only option was to use more As to signify than the new types were smaller than A. You can see a similar situation of wire gauges, its why we have 00, 000, etc.&nbsp;<h2>What Is The Most Common Type Of Battery Used Today?</h2>Lithium‑ion batteries are the most common type of battery used on earth today. This is because lithium ion batteries have such a high energy density, a high single cell voltage compared to other battery types, a low self‑discharge rate and no memory effect. They also have a long cycle life compared to other rechargeable batteries. Lithium ion batteries can be charged quickly, they’re extremely scalable and have form‑factor flexibility in their construction, and everybody’s making them right now. So the costs are coming down through economies of scale, and the battery‑management systems used to govern them have become extremely sophisticated, reliable, and low‑cost over time.Well, that pretty much covers it for what are the main types of batteries used today. We hope this article helped you learn more about the portable power landscape, thanks for reading!

What Are The Main Types Of Batteries Used Today?

Measure Internal Resistance With A Multimeter

Discover a straightforward method to calculate the internal resistance of lithium-ion batteries using a multimeter. Learn how to assess voltage drop, current, and battery efficiency in real-world conditions.

How To Measure Internal Resistance With A Multimeter

Measuring a lithium-ion cell’s internal resistance is super strait forward.: all you have to do is get three readings and do a bit of math. First, record the cell’s open-circuit voltage with no load attached. Next, apply a known load (or any practical load) and immediately note both the loaded voltage and the current flowing. Finally, subtract the loaded voltage from the open-circuit voltage to find the millivolts of drop, then divide that millivolt drop by the load current, and this will give you the cell’s internal resistance in milliohms.This single figure captures all the tiny ohmic losses hiding inside the metal, electrolyte, and connections of your cell. With that number, you can quantify efficiency under real-world loads.<h2>Understanding Inefficiencies and Ohmic Losses</h2>Nothing is 100 % efficient—there are always losses in any energy conversion or transfer. By identifying the processes that create those losses, we can calculate them rather than just wonder where they occur. In the case of extracting energy from a lithium-ion cell, most losses stem from ohmic resistance. Every conductor, even the most “ideal” ones, has some finite resistance determined by its material properties and geometry. To see how this plays out in a full health-check routine—including capacity tests and C-rate profiling—check out our <a href="https://cellsaviors.com/blog/steps-battery-testing">Battery Health Testing Process for Lithium-Ion Cells.</a>&nbsp;<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:907784,&quot;height&quot;:1024,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/VgI01XRjehc18wOnxGYpyGDZK3zmh0nsjZ6gs9hJ.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/VgI01XRjehc18wOnxGYpyGDZK3zmh0nsjZ6gs9hJ.png&quot;,&quot;width&quot;:1024}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/VgI01XRjehc18wOnxGYpyGDZK3zmh0nsjZ6gs9hJ.png"><img src="https://admin.cellsaviors.com/storage/VgI01XRjehc18wOnxGYpyGDZK3zmh0nsjZ6gs9hJ.png" width="1024" height="1024"><figcaption class="attachment__caption">image.png 886.51 KB</figcaption></a></figure><h2>What Determines Resistance?</h2><ul><li>Material: Copper and nickel paths of identical dimensions exhibit very different resistances—copper being far more conductive.</li><li>Geometry: A wide, flat plane of material has much lower resistance than a long, narrow strip of the same metal.</li><li>Cell Construction: In a battery, resistance arises from the casing, current collectors, electrode materials, electrolyte chemistry, and their interconnections—some in series, others in parallel.</li></ul>Ultimately, though, only the total internal resistance matters. We can measure it indirectly with any standard multimeter by comparing the cell’s voltage under no load to its voltage under load.<h2>Preparing to Measure Internal Resistance</h2>Regardless of the method you choose, you must:<ol><li>Measure the open-circuit voltage of the cell (no load attached).</li><li>Measure the loaded voltage immediately after connecting your load.</li></ol>The difference between these two readings, divided by the load current, yields the millivolt-per-amp drop, which directly corresponds to milliohms of internal resistance.<h2>Method 1: Known Resistive Load</h2>If you have a purely resistive load of known value, you don’t need to measure current directly—just apply Ohm’s law.<ol><li>Select your load resistor(s).<ul><li>Two 6 Ω resistors in parallel → 3 Ω total.</li></ul></li><li>Record the unloaded voltage.<ul><li>4.100 V.</li></ul></li><li>Connect the 3 Ω load and record the loaded voltage.<ul><li>4.010 V.</li></ul></li><li>Current &nbsp;I = Vloaded / Rload = 4.010 V / 3 Ω = 1.337 A</li><li>Voltage drop &nbsp;Delta V = Vopen – Vloaded = 4.100 V – 4.010 V = 0.090 V = 90 mV</li><li>Millivolts per amp and internal resistance &nbsp;Delta V per amp = 90 mV / 1.337 A ≈ 67.3 mV per A Internal resistance ≈ 67.3 mΩ</li></ol><h2>Method 2: Measured Current Load</h2>If you lack a known resistive load but can measure current, follow these steps:<ol><li>Connect your load (e.g., a motor or other device) to the cell.</li><li>Measure the open-circuit voltage. 4.100 V</li><li>Under load, simultaneously measure: Loaded voltage (4.010 V). Load current (with your multimeter in series (1.38 A).</li><li>Calculate Voltage drop &nbsp;Delta V = 4.100 V - 4.010 V = 90 mV</li><li>Determine Millivolts per amp and internal resistance &nbsp;90 mV / 1.38 A ≈ 65.2 mV per A Internal resistance ≈ 65.2 mΩ</li></ol><h2>Interpreting Your Results</h2><ul><li>Millivolts per amp = Milliohms. Once you have the mV/A figure, you’re done. </li><li>Efficiency guideline: Stay at or above 90 % efficiency under your expected load. In practical terms, ensure the voltage doesn’t sag by more than 10 % under typical current draw.</li></ul>Even with a basic $9 multimeter, you can achieve accuracy sufficient for most portable-electronics projects. More expensive meters simply yield tighter tolerances—but the principle remains the same. I cannot stress enough how important it is to be aware of voltage drop and its effects on not just a battery, but the entire circuit. If you know nothing about batteries, resistance, or anything like that, you can still compare the health and quality of various battery cells, simply by comparing how their voltages drop under the same kind of load.&nbsp; The battery cell that drops voltage the least with all else being equal is going to be the better battery cell.&nbsp;<h2>Do Multimeters Have High Internal Resistance?</h2>Yes. Multimeters have a very high internal resistance, generally on the order of 10 MΩ This wont make much of a difference when measuring voltages, but when measuring currents, it can cause quite a bit of error in cheap multimeters. The high resistance of a multimeter makes it safe to probe even very high voltages.&nbsp;<h2>Conclusion</h2>Measuring the internal resistance of a lithium-ion cell is a straightforward process: by comparing the cell’s open-circuit voltage to its loaded voltage under a known resistance or current, you can determine the voltage drop caused by internal losses. Dividing that millivolt drop by the corresponding load current directly yields the cell’s internal resistance in milliohms. Armed with this simple yet powerful method, you gain a clear, quantitative understanding of how much energy is dissipated inside your battery, helping you to optimize designs and troubleshoot performance in any portable-power application. If you’re ready to take individual cells and turn them into a robust pack, see our step-by-step guide on <a href="https://cellsaviors.com/blog/building-a-battery-pack-from-18650-cells">Building a Lithium Battery Pack from 18650 Cells.&nbsp;</a>We hope this article helped you learn more about how to measure internal resistance with a multimeter. Thanks for reading!

If you plan on designing a DIY solar setup for your home, shed, or RV, the heart of the system will be the battery bank

LiFePO4 battery banks in parallel

If you plan on designing a DIY solar setup for your home, shed, or RV, the heart of the system will be the battery bank. While there are several chemistries to choose from, LiFePO4 is often the best choice for home energy systems for several reasons. At some point you will be asking yourself, “How do you safely and efficiently connect multiple LiFePO4 battery banks in parallel?” &nbsp;(You can also check out our full guide on <a href="https://cellsaviors.com/blog/parallel-lithium-batteries">how to wire lithium batteries in parallel to increase amperage</a>.)&nbsp;Wiring LiFePO4 batteries in parallel is simple. All you have to do is connect all the positive terminals together and all of the negative terminals together. There is, however, some nuance involved depending on how much current your running, and how balanced your parallel connections are.In this article, we’ll go over all the ways you can wire LeFePO4 batteries in parallel, and we will explain how to maintain a proper balance of current when doing so.&nbsp;<h2>Why Choose LiFePO4 for Your Home Energy System?</h2>Lithium iron phosphate batteries have several different properties compared to the traditional NMC chemistry that most lithium-ion batteries use. And the most important one is the cycle life. Your typical NMC lithium-ion battery can be recharged 500–800 times before it's considered end of life, at which point it only holds 80% of the capacity that it used to, and its internal resistance will have by then increased dramatically.Lithium iron phosphate batteries, on the other hand, can last 2,000, 3,000, or even 4,000 cycles, depending on the quality of the cells and how you use them.&nbsp; Also, they have a more ideal voltage range for home energy applications, because most of the equipment that's used for home energy solutions — such as inverters, charge controllers, etc. — are made for either a 12 or 24-volt voltage range.Systems and their components exist outside of those values, but most of the time, home energy systems are either going to be in the 12 or 24-volt range.NMC In 24-Volt SystemsIt's relatively easy to make something 24-volt compatible using NMC cells because you can just put 7 in series. The full charge voltage would be 29.4 volts, the nominal voltage would be 3.7 times 7, which would be 25.9 volts, and the dead voltage would be about 2.8 times 7 for about 19.6 volts.So you've got around a 20 to 30-volt range with a 7S NMC lithium-ion battery. And because most 24-volt devices can work well within and even beyond that range, you won't have any problems.NMC In 12-Volt SystemsBut when you try to make 12 volts, you run into an issue. If you want to make 12 volts with NMC cells, you can try to put either 3 or 4 in series. Let's do both:<ul><li>3 times 3.7 is 11.1 volts, so that's close enough to 12 volts for the nominal voltage. But if you do the dead voltage around 2.8 times 3, you're down to 8.4 volts. Even if you raise your cutoff voltage to 3 volts, you're down to 9 volts. That's too low to operate a 12-volt system. </li><li>So let's try to add another cell in series. For 4S, we have a nominal voltage of 3.7 times 4. Well, that's 14.8. That's a little higher than 12 volts. It'd probably be okay. Most equipment that's made to run at 12 volts will cut off around 15 volts or something like that on the high end. So it would probably be okay.</li></ul>But remember, that's just the nominal voltage. That means you're losing all the capacity north of nominal voltage, because 4.2 times 4 is 16.8. That's way too high for any 12-volt system.LFP In 12-Volt SystemsBut we can compare that now to LFP. With LFP, you have a 3.7-volt maximum voltage and a 3.2-volt nominal voltage.&nbsp; So 3.7 times 4, and we get 14.8. That's the max charge voltage. That's about what an alternator puts out when it's charging your car, which is a 12-volt lead-acid battery. And then when those batteries are dead, around 2.8 volts, multiply that by 4, and we have 11.2. That's still well within the acceptable operating range of a 12-volt system.So, for any 12 volts system that's based on lead acid voltage ranges (and most are), the best type of battery to use is LFP. Doing that will ensure that you will be able to run your 12V equipment, regardless of the state of charge of your LFP cells in parallel.<h3>Why LFP Is Ideal For Home Energy Storage</h3>LFPs extremely high cycle life and its voltage range is what really makes them so ideal for home energy storage.&nbsp;The one big drawback of LFP is that they're much lower energy density than NMC. So they're going to be larger. They're going to have more volume. They're going to be heavier compared to an equal-capacity NMC battery. But the thing is, for home storage, that doesn't matter. That matters if you're doing an e-bike battery or something like that, that has to be small, compact, and lightweight. At that point, you would want to use NMC because it's got the best energy density.But for home energy storage, it doesn't have to be ultra-compact. And these batteries are still much more light, much more compact, and much more energy dense than the lead-acid batteries that they replace. And they last a whole lot longer. So for those reasons, LFP is definitely the best way to go for home energy storage.<h2>Wiring LiFePO4 Battery Banks In Parallel</h2>Can One 100Ah LFP Battery Power a House?You might think if you're just starting out that you could get a single 100 amp hour 12-volt LFP battery and run your entire house, but just not for very long. That's not the case because most of these batteries have around a 200 amp discharge current limit. At a nominal voltage of 12.8 volts, 200 amps is just 2.56 kilowatts.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:716809,&quot;height&quot;:970,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/OfiPLxGnTdeciGv7aJedFujOFs1dE0dmqQG5qxou.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/OfiPLxGnTdeciGv7aJedFujOFs1dE0dmqQG5qxou.png&quot;,&quot;width&quot;:2000}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/OfiPLxGnTdeciGv7aJedFujOFs1dE0dmqQG5qxou.png"><img src="https://admin.cellsaviors.com/storage/OfiPLxGnTdeciGv7aJedFujOFs1dE0dmqQG5qxou.png" width="2000" height="970"><figcaption class="attachment__caption">image.png 700.01 KB</figcaption></a></figure>The average American household uses somewhere between 4 and 7 kilowatts of energy at any given point. It can go lower or higher than that, but that's a decent average to consider. So that means you have to put LFP batteries in parallel for increased current, even if you don't want the added capacity that comes along with that.<h2>Wiring LiFePO4 Battery Banks In Parallel: Two Methods</h2>There's two ways to wire batteries in parallel. You can do a simple daisy chain setup where one battery connects to the next battery in a row, and at one end of the row you'll have your positive and negative connections for energy to go in and out of the battery bank.Or you can do a star topology where all the batteries have the same length cables and connect to some central point.The Daisy Chain ArrangementThe first one we'll cover is the daisy chain arrangement. This can work fine in many applications as long as you consider:<ul><li>the amount of current that you're going to draw,</li><li>the amount of current that each battery can support, and</li><li>the amount of current that your parallel connections can take.</li></ul>For example, if you have three 100 amp hour LiFePO4 batteries wired in parallel and they can each do 200 amps of current, that means the battery bank as a whole can do 600 amps of current.Your series connections are extremely important when you're wiring LiFePO4 battery banks in parallel. If the cables can only do 200 amps each and you put a 600 amp load on the battery, in an ideal world each battery would see 200 amps of the load because it would be split three ways.But remember they're all connected with the same 200 amp cable, and the electrons will take the path of least resistance. So if you have one long cable that's the same width the whole way down, the further and further you go, the higher and higher the resistance.That means even if all of your LiFePO4 battery banks have the same resistance and they can all handle a very high current, if you have them in a daisy chain and you draw a high current from them, the battery closest to the terminals — the output — will see most of the load.It will be somewhat split amongst the batteries, but most of the load will be seen by that first battery. Its voltage will drop more than the batteries at the end because the batteries at the end are seeing a much lighter load.And then in an instant, right then and there, the batteries at the end will be charging the batteries closer to the terminals. This happens very quickly and ultimately isn't dangerous, but it does reduce the life of the batteries.Improving the Daisy Chain SetupThe best way to wire LiFePO4 battery banks in parallel, if you're going to do the daisy chain method, would be to use more and more cable to connect each battery further and further down the line.So you might use one positive and one negative cable for the first two batteries. And then for the next two batteries, you can use two positive and two negative cables. And then for the next two batteries, use four positive and four negative cables.That way, you don't have to use so many cables the whole way down, and doing this will help even out the resistance.If you don't want to do all that, then just make sure to keep your load at about half of your total current. So if you can support 600 amps, do 300 amps on the battery bank and it'll be just fine. But it will have a slightly reduced life because of that.The Star Topology ArrangementThe other way is by organizing them in a star topology. If you have all of your batteries surrounding an area where you want to put your terminals, you can simply use the same length cable to connect all of those batteries to that common terminal. This will make a circular-shaped setup, but it makes it extremely easy to get balancing just right.You could obviously arrange the batteries any way you want and just make sure you use the same length cable for each battery. But you'll end up with a bundle of cables somewhere or in multiple places if you do that — which is why I suggested the radial arrangement for connecting LiFePO4 battery banks in parallel while maintaining the balance of the parallel connections.<h2>Conclusion</h2>Whether you're expanding your DIY solar storage, setting up a battery backup generator, or preparing for the next power outage, understanding how to wire LiFePO4 battery banks in parallel is key.With the right wiring, proper charging using MPPT controllers,&nbsp; (learn more about the difference between <a href="https://cellsaviors.com/blog/mppt-pwm-solar-charge-controller">PWM and MPPT solar charge controllers</a>) , reliable equipment like Victron inverters, and smart safety practices, your battery bank will deliver dependable, long-lasting performance for your home, shed, RV, or off-grid retreat.

LiFePO4 Battery Banks in Parallel

This regulator board is really great with a power switch right there, but you can also control the output with the screen. 

Regulator board

<h2>Regulator Board Overview</h2>This regulator board is really great. It's a constant current buck converter, which means it lets you control the current and voltage settings. A buck converter, whether its constant current or not, can only reduce the voltage. It does not have the ability to increase the voltage. In this case of this buck converter, its almost not a problem at all. That's because this regulator board supports a relatively high 55V make input voltage.&nbsp;That means this regulator board can be attached to a 48V lithium ion battery, and be used as an excellent portable power supply that can also charge a wide array of other lithium ion batteries.&nbsp;<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:933151,&quot;height&quot;:720,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/j6xUep4o2wyXceRWl4i7w1yIkBpSQyDnanTY9vXb.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/j6xUep4o2wyXceRWl4i7w1yIkBpSQyDnanTY9vXb.png&quot;,&quot;width&quot;:1280}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/j6xUep4o2wyXceRWl4i7w1yIkBpSQyDnanTY9vXb.png"><img src="https://admin.cellsaviors.com/storage/j6xUep4o2wyXceRWl4i7w1yIkBpSQyDnanTY9vXb.png" width="1280" height="720"><figcaption class="attachment__caption">image.png 911.28 KB</figcaption></a></figure> Here, on the left side of the board, you can see the input. It's just those basic screw terminals, so you don't need any special equipment to use this board. <figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:1238537,&quot;height&quot;:720,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/MRlFcJ0HjojldcrhGTC0uMDjxSXdmESUo7v4ePt6.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/MRlFcJ0HjojldcrhGTC0uMDjxSXdmESUo7v4ePt6.png&quot;,&quot;width&quot;:1280}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/MRlFcJ0HjojldcrhGTC0uMDjxSXdmESUo7v4ePt6.png"><img src="https://admin.cellsaviors.com/storage/MRlFcJ0HjojldcrhGTC0uMDjxSXdmESUo7v4ePt6.png" width="1280" height="720"><figcaption class="attachment__caption">image.png 1.18 MB</figcaption></a></figure> Here's the connections for the screen. Even though the connectors are the same for the screen, it's really easy to remember how to hook it up because the left side on the screen goes to the left side on the board, and the right side on the screen goes to the right side on the board.<figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:1144842,&quot;height&quot;:720,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/GTRlZxIpOFjFJB7wA3nGO1EuUKerdYErvmUgJ0UB.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/GTRlZxIpOFjFJB7wA3nGO1EuUKerdYErvmUgJ0UB.png&quot;,&quot;width&quot;:1280}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/GTRlZxIpOFjFJB7wA3nGO1EuUKerdYErvmUgJ0UB.png"><img src="https://admin.cellsaviors.com/storage/GTRlZxIpOFjFJB7wA3nGO1EuUKerdYErvmUgJ0UB.png" width="1280" height="720"><figcaption class="attachment__caption">image.png 1.09 MB</figcaption></a></figure>There’s a power switch in the corner, but you can also control the output with the screen. <figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/jpeg&quot;,&quot;filename&quot;:&quot;微信图片_20250428100434.jpg&quot;,&quot;filesize&quot;:125204,&quot;height&quot;:720,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/rcxTbNkElCCkmLyLs7lCahYbpKQB5RyOPWg5xbxO.jpg&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/rcxTbNkElCCkmLyLs7lCahYbpKQB5RyOPWg5xbxO.jpg&quot;,&quot;width&quot;:1280}" data-trix-content-type="image/jpeg" data-trix-attributes="{&quot;caption&quot;:&quot;Regulator board&quot;,&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--jpg"><a href="https://admin.cellsaviors.com/storage/rcxTbNkElCCkmLyLs7lCahYbpKQB5RyOPWg5xbxO.jpg"><img src="https://admin.cellsaviors.com/storage/rcxTbNkElCCkmLyLs7lCahYbpKQB5RyOPWg5xbxO.jpg" width="1280" height="720"><figcaption class="attachment__caption attachment__caption--edited">Regulator board</figcaption></a></figure>Here is the output, on the right side of the board. It uses the same screw terminals as the input.&nbsp; A lot of regulator boards sold on Amazon and elsewhere claim a certain current rating, but in reality, come nowhere close. This regulator is different. It really can do what it claims to be able to do, and you don't have to modify it in any way for it to do so. So, that means you don't have to add a heatsink, a fan, or change out any connectors.&nbsp;<h2>Input Voltage and Capacitors</h2>On the Amazon page, it says a max input of 50 volts. It depends on the listing you're looking at and which part of the listing you're looking. But I can tell you it has 63-volt input capacitors and 63-volt output capacitors. I haven't checked the tolerances of the other chips, but I've run this reliably with a 55 volt input with no problems.As far as the output, the maximum of that output is going to be about a volt and a half lower than whatever the input is, but it still has its own maximum. I believe that's 51 volts.<h2>Fan and Thermal Protection</h2>It has a fan and that fan is really well done. What's special about the fan? Nothing. It's a cheap, low voltage, low current fan. It's the control system they're using that's nice. The fan only kicks on when it really needs to, and if that fan's running, this thing is not going to be hot – maybe just warm to the touch. You'd have to put it in extreme circumstances like maxing out the output current at 20 amps while having like a 40-volt difference between the input and the output for this thing to struggle. And if it does, it will cut off before anything gets damaged. I haven't had these burn up on their own. The only way I've broken these is by damaging the board, hooking it up backwards, or doing something else stupid. This thing works just as good as it says it will.<h2>Curious Connections and Screen Functionality</h2><figure data-trix-attachment="{&quot;contentType&quot;:&quot;image/png&quot;,&quot;filename&quot;:&quot;image.png&quot;,&quot;filesize&quot;:1723256,&quot;height&quot;:762,&quot;href&quot;:&quot;https://admin.cellsaviors.com/storage/KxdDW20YCjhZOl9QHB8eDVHIBz0l6h1xp2QziWzS.png&quot;,&quot;url&quot;:&quot;https://admin.cellsaviors.com/storage/KxdDW20YCjhZOl9QHB8eDVHIBz0l6h1xp2QziWzS.png&quot;,&quot;width&quot;:1447}" data-trix-content-type="image/png" data-trix-attributes="{&quot;presentation&quot;:&quot;gallery&quot;}" class="attachment attachment--preview attachment--png"><a href="https://admin.cellsaviors.com/storage/KxdDW20YCjhZOl9QHB8eDVHIBz0l6h1xp2QziWzS.png"><img src="https://admin.cellsaviors.com/storage/KxdDW20YCjhZOl9QHB8eDVHIBz0l6h1xp2QziWzS.png" width="1447" height="762"><figcaption class="attachment__caption">image.png 1.64 MB</figcaption></a></figure>It also has these curious connections in the corner of the board between the screen connectors. I’ve probed them while it’s running and while I'm changing settings. Some of these pins seem to be voltages that are proportional to whatever current and voltage that you set it to. I’ll have to look into that more later.Regardless of those pins and what they might do, there is opportunity here because I do believe the screen is I²C. If it's not I²C, it's some sort of basic digital protocol. So this cheap, low-quality screen could easily be replaced, and that's great because the cheap screen is the only complaint I have about this regulator.<h2>Applications and Performance</h2><h3>Powering Lower Voltage Devices</h3>What can you do with this regulator board? The most obvious thing to do with a <a href="https://cellsaviors.com/blog/buck-boost-converters">buck converter</a> is to power a lower voltage device with a higher voltage input.&nbsp;Suppose you’ve got a gadget rated for 12 V but only a 24 V battery in your toolbox. Dial the supply’s voltage down to 12 V and set a current limit above your device’s draw (say, 1 A), then feed the supply from whatever DC or AC source you choose. The internal regulator “drops” the excess voltage so your gadget sees a clean, stable 12 V and can’t pull more than the 1 A you allowed. Alternatively, if you have a separate DC‑DC converter, you’d configure it in exactly the same way: desired voltage and current limit, and it automatically adjusts its output around your load’s needs.So, consider something like a 12 volt LED strip. 12V strips can be ran at a little bit over 12 volts if you want some extra brightness at the expense of a lower operational lifespan. But you don't want to go too far; you definitely don't want to put 30 volts into it. It won't last very long and it'll get very hot. Its good to set the output voltage to somewhere around 14 and a half volts. If you go any higher than that and you're just not getting the brightness that you deserve for the power that you're putting into it.<h3>Alternative Uses: Multimeter Functionality</h3>You can actually stretch a simple adjustable DC bench supply into three surprisingly useful roles, all without firing up a true multimeter or charger. First, you can use it as a makeshift voltmeter: simply crank the supply’s output voltage to a value you know exceeds the unknown source, then dial the current limit down to zero.When you clip the leads onto your 7‑cell pack (nominally around 25 V), the supply immediately collapses its output to the battery’s actual open‑circuit voltage—say, 24.93 V—and since the current is set to zero, no current flows at all. It’s not a substitute for a real meter—you’ll lack reverse‑polarity protection and proper input impedance—but in a pinch it tells you the battery’s voltage without sourcing or sinking any current.<h3>Battery Charger</h3>Next, you can turn that same supply into a constant‑current, constant‑voltage battery charger. After measuring the pack at, say, 24.9 V, bump the supply’s voltage up to something safely above it—27 V works nicely—and set the current knob to your desired charge rate, for example 2 A. Plug in, and the supply automatically throttles its voltage down (to roughly 25.9 V in this case) so that exactly 2 A flows into the battery. If you then reduce the current limit to 1 A, you’ll watch the output voltage shift to around 25.6 V, because that’s the voltage required to push 1 A into the pack. Voilà: a DIY CC/CV charger.This regulator board makes a great custom battery charger, because you can set the voltage precisely. For example, if you have a 48V lithium ion battery, it has a full charge voltage of 54.6V. The problem is, that is 4.2V per cell, which is the absolutely maximum voltage that the cells can handle. You can charge your battery to 4V per cell, you will get a lot more life out of it in exchange for a small amount of capacity loss.&nbsp; With a normal charger, you can't do that. And chargers that are adjustable are often either expensive or poorly made. With this regulator board, however, all you have to do is set the output voltage to 52 volts. This will charge your 48V battery to 4V per cell, extending its overall lifespan.&nbsp;<h2>Battery-to-Battery Charging</h2>You can do exactly the same trick with a constant-current buck-converter regulator by using your higher-voltage pack as the “input rail” and letting the module’s CC/CV loop handle both current limiting and voltage regulation. To charge a 12 V battery from a 48 V source, first confirm the buck converter’s input stage can accept the full 48 V. Then adjust its output voltage pot to your battery’s recommended absorption or float voltage (for instance, about 14.4 V absorb and 13.6 V float on a lead–acid, or roughly 13.6 V for LiFePO₄) and set the current limit to the desired charge rate (e.g. 3 A for a 30 Ah lead–acid, or 0.1 C).Connect the 48 V pack to the converter’s VIN/GND terminals, clip its VOUT/GND leads onto the 12 V battery (mind the polarity), and the buck converter will step the higher voltage down to your setpoint, automatically throttling current until the battery’s voltage rises near the set value. At that point its CV loop takes over, holding the programmed voltage while the charge current tapers to zero and then maintaining a safe float.The same arrangement works for charging a single Li-ion cell (≈3.7 V nominal) from a 36 V pack. Hook up the 36 V battery to the input of the buck converter, and then simply set the output voltage to 4.20 V and the current limit to, say, 0.5 A (0.5 C for a 1 Ah cell). Then attach the cell to the output, and let the buck module automatically step down and regulate. It will supply a steady 0.5A while letting the voltage go to whatever it needs to be to maintain that current, up to the maximum set voltage of 4.2V. After that phase is complete, the regulator switches into CV mode keeps the voltage locked as current tapers off.&nbsp;<h2>Using the Regulator for Cell Group Charging</h2>You can also use a constant current buck converter to safely charge a cell group while its in series with other cells. All you have to do is connect the positive of the regulator output to the positive of the cell group, and the negative of the regulators output to the negative of the cell group that you are interested in. As long as the connections are touch just those places and no other places, you wont have any problems.&nbsp;All of these tricks rely on one simple fact: an adjustable bench supply is just a programmable voltage source with an adjustable current ceiling. Clamp the current at zero and it functions like a voltmeter; clamp the voltage and it acts like a charger; dial in a fixed voltage and it becomes a regulated power rail. The amperage you see is merely the load drawing whatever current Ohm’s law dictates at that voltage. Three tools in one little box<h2>Conclusion</h2>These 1000W buck converters are an incredible value. You get a robust, versatile power module that handles a wide range of input voltages and delivers adjustable outputs in both voltage and current. Whether you’re powering non-battery devices from a DC supply, AC mains, or even charging batteries, this little board does it all—and then some. You can <a href="https://www.amazon.com/EC-Buying-Adjustable-Converter-Regulator/dp/B0B38GYF74?tag=cellsavior08-20">grab yours on Amazon</a> for under 30 bucks.

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