New Vs Used Lithium Ion Batteries and CellsPosted on: Tue Nov 08 2022
Using new vs used lithium-ion batteries for a particular project can be a challenging choice. Using used lithium-ion batteries helps the environment and can save you a lot of money while using new lithium-ion batteries ensures consistency and good performance.
As long as you either do proper testing or get your used battery cells from a company that does, then when it comes to new vs used lithium-ion cells, there is no difference in performance. As long as you know what the cells are capable of and what to expect from them, and the cells are not worn down too much (which can be determined with proper testing), then you won’t have any problems. Using new cells makes the selection process easier and there is often less work required to get them build-ready. They are more expensive, but you know they will all be at a full state of health and will probably last longer than used cells that can perform equally well.
In this article, we will talk about the pros and cons of using new vs used lithium-ion batteries. We will also go over a few things that used lithium-ion batteries can be used for.
What's Inside A Battery?
When a battery pack goes bad only a few cells in the pack are actually damaged. Many used lithium cells still have plenty of power left in them. As long as you test the used cells well or buy them from a place that does that testing for you, used lithium-ion cells can be just as good as new cells.
A battery cell contains an anode and cathode separated by non-conductive material called an electrolyte. Over time the materials inside a battery degrade. The degradation usually results from the buildup of material on the electrodes that causes them to start to connect to the other side. This will happen if you over-current the battery or if the battery has been cycled many times.
What Is The Voltage Of A New Lithium Ion Battery
About 3.7 volts on average, which is the same for a used lithium-ion battery. Batteries only have a steady voltage when they are not being used. While a battery is being used its voltage is a curve when plotted over time. So that means when you see batteries being listed as being 48 volts or 72 volts, it's not exactly accurate. For example, to make a '48-volt' lithium-ion battery, you need to have 13 cell groups in series.
That set of batteries will have a maximum charge voltage of 54.6 volts and a dead voltage of about 34 volts. So why is that considered a 48-volt battery? It's because the average cell voltage of a lithium-ion cell over its entire discharge curve is around 3.7 volts.
3.7 volts x 13 cell groups in series = 48.1 volts
So, the voltage curve for a 48-volt battery goes like this: At first, when it's fully charged, it will be 54.6 volts. Shortly after that, the voltage will start to drop toward the lower 50s. Over the course of use from this point, the battery voltage drops slowly. Most of the battery's runtime will exist in this rage. Once the battery's voltage reaches around 40 volts, it will start to drop pretty steadily until it reaches its low voltage cutoff.
So, when you are working with individual cells and putting them in various series and parallel arrangements, it's important to keep their running voltages in mind so that you know what output voltage you will really be working with.
The voltage curve of a used battery cell will be exactly the same as a new cell of the same brand and model, but depending on how used the cell is, it may run through that voltage curve a little faster.
It’s important to remember that whether you are doing it yourself or buying them from a supplier, used lithium-ion battery cells come in many grades. Remember, batteries don’t age at the same rate. So, while it may be true that most cells in a bad battery pack are good, some of them may be past their prime.
Is It Dangerous To Use Used Battery Cells?
Using used lithium-ion cells safely requires an understanding of lithium-ion batteries and how they work. It also requires testing and grading of the cells. As long as the cells are properly categorized in terms of what kind of power they can provide, then it's not dangerous to use them. If, however, you use a lithium-ion cell at its rated current levels when it's far beyond the ability to be able to do that due to its health, then it could be dangerous.
A battery that's been used a lot is going to have a far higher internal resistance than a new battery. Buying used batteries means you don’t know how many times a cell has been cycled. You also don’t know how much current that cell was put under. This is why testing and grading are so important. As long as you test cells for voltage and internal resistance, then you can get a good measure of how healthy a cell is.
Pros And Cons Of New Vs Used Lithium Ion Batteries
New Lithium Ion Batteries
- Easier to shop for
- Consistent supply
- Known characteristics and history
- Usually pre-balanced
- Places toll on infrastructure during manufacture
Used Lithium Ion Batteries
- Low Cost
- Lower overall environmental impact due to re-use
- Sometimes free
- Unknown history (testing required)
- Balance required before build
What Can Used Lithium Cells Be Used For?
You can use used lithium-ion cells for just about anything! There are many cases in which used lithium-ion cells are just as good as brand-new cells. So as long as you know what your cells are capable of, then you can use them in just about any application you would use a new lithium-ion cell for.
Also, used cells are much cheaper than brand-new lithium-ion cells. The lower cost of used cells makes them candidates for projects that would otherwise not be economically feasible otherwise.
If you are new to building batteries, used lithium-ion battery cells can seem questionable or even dangerous. If you know what to look for and know how to test them, however, then you can ensure that you are operating the cells within their limits.
Used lithium-ion battery cells can be used for anything that new lithium-ion cells are used for. Correctly building and safely using batteries made from used lithium-ion cells is possible if you properly test and grade the cells you plan on using. As long as you don't overstress any particular cell, and the cells you are using are closer to the beginning of their lifespan, then you won’t notice any difference between the two.
We hope this article helped you learn more about new vs used lithium-ion batteries and cells, thanks for reading!
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