A 38120 battery cell is a lithium iron phosphate (LFP) cell characterized by its dimensions: 38mm in diameter and 120mm in height, primarily manufactured by the brand Headway.

Headway 38120 Battery Cells

Headway is a major producer of 38120 battery cells. Headway cells are known for their absurd levels of current carrying capacity and ease of use. Headway cells are very large. They are 38 mm by 120 mm. LFP cells are not the most energy dense, but because of their large size, 38120 have a capacity of 8Ah, which is way more than any 18650 or even 21700. The most significant feature of the 381280 is the enormous amount of current you can draw from them. Headway cells can deliver 200 amps of continuous current, which is way, way higher than any 18650 or 21700 cells. 

Due to their design, Headway 38120s have an extremely low ISR (Internal Series Resistance). This low internal resistance means these cells can remain cool under high current loads. If you push them to anywhere near their maximum output, however, you can expect them to get hot. But that means that these cells can deliver 50-100 amps before they start getting uncomfortably warm. 

Understanding Battery Performance and Heat Management

The amount of current that a battery cell can deliver is determined by how much heat it generates. The amount of heat generated is due to the internal resistance and the internal resistance relates closely to the cells internal properties, such as cathode and anode materials, design, and placement. These factors collectively influence the amount of heat produced, which needs to remain within a tolerable level for safe operation.

For instance, if a cell reaches around 65 degrees Celsius when under a constant load of 45 amps, then 45 amps would be the upper limit for that cell. So, a cell that is rated for 200A will always have a lower internal resistance than a cell that is rated for 45A if those cells are the same physical size. 

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Ease of Use and Durability of 38120 LFP Cells

Other than the massive current carrying capability, another major benefit of LFP cells like Headway 38120s is their user-friendliness. To work with these cells, you don't need any welding or soldering equipment. Using these cells is as simple as bolting them together because they come with ultra-convenient screw terminals.

Another benefit that Headways have comes from the fact that they are LFP. LFP chemistry can handle 2000+ cycles before you see any kind of capacity degradation. In contrast, NMC cells tend to drop to 80% capacity after around 500-800 cycles.

Voltage and Current Considerations

LFP cells have a lower nominal voltage compared to NMC technology, which means you have to use more LFP cells in series to achieve an equivalent voltage NMC voltage. This is made up for, however, with the large current delivery capacity that the 38120 cells can deliver, because you don’t need so many cells in parallel. With these Headway  LFP cells, parallel additions are only required to add capacity. 

Also, there is a massive benefit that comes from having a lower voltage. With the lower 3.25 nominal voltage, 4 of these cells can be put in series to match the voltage curve of a lead acid battery. This makes it so Headway and other LFP cells can be used to power all kinds of equipment without regulators. It also means that with the properly tuned setup, you can even charge a 4S LFP battery without a regulator using an alternator, but really, I don't recommend ever charging a lithium-ion battery without a proper constant current regulator. 

Versatility of 38120 Battery Cells

Headway 38120s are incredibly versatile and easy to use, so they are often found in car audio battery systems, home backup power solutions, and various high-power projects where space is not the primary concern. Their ease of use negates the need for professional battery builders or complex equipment like spot welders, making them suitable for hobbyists and DIY enthusiasts. All it takes to effectively use these cells is a basic understanding of electronics, batteries, and the right components, opening up a wide range of potential use cases.

Where to Buy 38120 Cells

There are primarily two ways to source 38120 battery cells - either by buying used cells or new ones. Depending on your specific needs and budget, both options have their own advantages and disadvantages.

If cost is the most important factor, then buying used 38120 cells can be a viable choice. A reliable source for these used cells is Battery Hookup. They offer a variety of battery cells, including Headway 38120s. Buying used cells from reputable sources like Battery Hookup can be a cost-effective way to acquire high-performing cells. It’s important to keep in mind that while their quality control and testing methods are typically reliable, these cells may have some wear or a reduced lifespan due to previous usage.

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On the other hand, if cost isn’t too much of an issue or you simply prefer to purchase new 38120 battery cells for maximum performance and lifespan, then Sriko batteries is where to get them. They offer new Headway 38120 cells that are straight from the factory, ensuring that you're getting cells in top condition. Buying new cells might be more expensive than getting used ones, but it can provide you with the peace of mind of a brand-new product with its full lifespan ahead.

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