How To Break Down Lithium Ion Battery Packs

If you are wanting to work with lithium-ion batteries but you are light on cash, then you can always learn how to break down lithium-ion battery packs. If you know how to break down a lithium-ion battery pack, you can save yourself a lot of money on cells by buying bad battery packs and equipment that contains them for cheap.

Breaking down a lithium-ion battery pack is easy, it just requires care and patience. All you need are some basic hand tools and an understanding of how the batteries in the pack are connected together. With some effort, you can remove the nickel from the cells and remove the cells from the battery pack. After that, all you have to do is clean up the cells and test them. 

In this article, we will go over how to break down lithium-ion battery packs. We will also shed a little light on how batteries work and what makes a used battery different from a new one. 

Are There Good Cells In Bad Battery Packs?

Yes! When a battery pack 'goes bad' it's because the BMS has decided to shut it off for one of many reasons. Usually, it's because a single cell has failed. Battery packs are made of multiple cells grouped in specific ways. If one cell dies, it will bring down the cells that it is immediately attached to. This is bad news for the cells in that group but its good news for the rest of the battery pack. It generally means that the other cell groups are just fine.

How To Break Down Lithium Ion Battery Packs

Lithium-ion battery packs are welded together. So it's no small feat to separate the cells. In fact, breaking down a lithium-ion battery pack is a rather involved process that takes care and patience. You have to be extremely careful when breaking down a lithium-ion battery pack. If you're not, then you will easily short out cells. When you are working on the cell level, there is no BMS there to protect you. So proceed with caution.

Tools Required To Break Down Lithium Ion Battery Packs

When breaking down a lithium-ion battery pack, having the right tools for the job is critical. The tools you use to break down a lithium-ion battery pack can be the difference between salvaging a bunch of great cells and starting a fire. 

• Needle-nose pliers
• Sheer snips
• Silicone gloves
• Multimeter 

How To Remove Cells From Lithium Ion Battery Packs

If you are wondering how to remove cells from lithium-ion battery packs, the answer is 'Very carefully.' A BMS protects a battery pack (and the user) from 99 percent of things that can cause fire and serious injury. When you are breaking down a lithium-ion battery pack, you are basically dealing with the other 1 percent. There is no BMS there to protect the battery, you, your house, or your family. So, when you are breaking down a lithium-ion battery pack, proceed with caution. 

If you accidentally short out a complete battery pack with a BMS, you might make a big spark, partially temporarily blind yourself, and could possibly receive a small burn. If you short out a battery without a BMS, however, one of two things will happen. Either the connection that you shorted out will vaporize and burst into flames or the battery cell will become overloaded and 'vent with flame'. There is no third option and you definitely want it to be the first one. 

If you short out a cell or group of cells without the protection of a BMS either a very small very bad thing will happen or a very large bad thing will happen. Either way, it's something to avoid. 

Step 1: The very first step is to remove all supporting wires and other connections to the battery. Whatever the main battery pack is electrically connected to, remove it. Remove any circuit boards, regulators, lights, wires, or anything else there is, and get it down to the raw battery pack. 

Step 2: Mask off the area that you are not working on with Kapton tape or any other easily removable adhesive insulator. This makes it so if you drop a piece of metal on the battery pack, the chances of a short are highly reduced.  

Step 3: Use needle nose pliers to carefully roll back the nickel to peel off the welds. Do this with EXTREME caution on the positive end, as it is very easy to short out the cell through its shoulder. Make sure to always pull up and away from the battery pack, and be patient with the pieces you are trying to remove. Remember, the entire point of spot-welding a battery pack together is to make a strong connection. So, it's normal for this phase to be hard. 

Step 4: Now it's time to remove the nickel still left on the cells. Use the sheer snips to cut the nickel off of the top of the cell as flat as possible. In some cases, you will find that you can use the sheer snips as tiny grabbers to pull the small pieces of nickel completely off the cell for a totally smooth finish. The goal is to get the ends of the cells as flat as possible.

How To Test Lithium Ion Battery Cells

There is a lot you can do to test a battery cell, ranging from the very simple to the very complex. When doing the first phase of testing, a visual inspection and voltage check is required.  Further testing should be done, but as long as you do a charge test after that, chances are you will be able to use the battery safely. Check out our full guide to testing and grading lithium cells here.

Visual Inspection

Take a look at each cell. Check for rust and any signs of liquid leaking out. If you notice these things, then discard the cell. After all, there is no sense in testing a cell that is obviously damaged. 

Voltage Test

Use a multimeter to voltage-check the cells. Any cells that are below about 2.5 volts are going to be damaged to some degree. Any cell that is over 4.2 volts has been overcharged for whatever reason and is also going to be damaged to some degree. If you find any cells that are between 2.6 volts and 4.2 volts, then there is a good chance that the cell is good and has some life left in it. 

Charge Test

Now that all of your cells are separated, cleaned, and voltage tested, it's time for the charge test. Fully charge each cell to 4.2 volts using a lithium-ion battery charger. After the charge is complete, let them sit for a day or two. After that, check the voltage again and if the voltage falls by more than .1 or .2 volts in a few days, then chances are the cell in question has a high degree of self-discharge.

If you do those things then you will generally have good luck with breaking down lithium-ion battery packs. It’s best to use a charger that can perform an internal resistance check of the cells under charge. New lithium-ion batteries have an internal resistance of anywhere between 25 and 50 mOhms. A used but still very healthy battery will have an internal resistance of somewhere between 50 and 100 mOhms. If a battery cell has an internal resistance any higher than 120mOhms or so, then it's pretty much at the end of its life. 

Conclusion

Anyone looking into building batteries while saving some cash is going to need to know how to break down lithium-ion battery packs. 

The good news is that breaking down a lithium-ion battery pack is fairly straightforward. It can be very dangerous if you rush it, so it takes patience. No speciality tools are required, but it's helpful to know how the batteries are connected and some things to avoid, like shoulder shorts. After carefully separating, cleaning, and testing the salvaged lithium-ion cells, you will be able to use them for your project. 

We hope this article helped you learn how to break down lithium-ion battery packs. Thanks for reading!