Salvaging Rechargeables for Projects

Introduction: Salvaging Rechargeables for Projects

About: I'm a 18-year-old high school student, I love engineering, film production, design and everything in between.

lithium polymer and lithium ion batteries aren't extremely expensive but if you use them in a lot of your projects it can run up quite a big bill. So in this Instructable we are going to take a look at the different places you can find them for cheap or often free and how to make sure the ones we find are reliably able to hold a charge and are most importantly safe to use.

Step 1: What You'll Need

luckily taking apart cells and checking them isn't the hardest thing in the world to do but there are some tools that make it a lot easier and less time consuming these are:

  • A multimeter (will be using the voltage mode)
  • Lithium Charger (Get it here)
  • 18650 battery holder (Get it here)
  • a box cutter
  • a screw driver
  • Electrical fire extinguisher (I've never had a battery get short get hot or cause a fire but it is always safe to have one on hand just in case)

Step 2: Where to Find Them

Lithium is the most common type of rechargable battery used in consumer electronics, there are two types of lithium batteries that are used, these are lithium ion and lithium polymer, don't get these confused with no-rechargeable batteries like 9 volt, AA, AAA and some coin cells which are all made of alkaline if you attempted to charge these you'd not have a fun time. Tones of electronic devices use these batteries but the cheapest places to find them is in old laptops. If you go to ewaist facility and ask them for laptop batteries you can get them for reeeeeally cheap while you're there you might as well keep and eye out for anyother electronics that look like they might have a battery inside such as

  • Phones/Tablets
  • GPS systems
  • Power Banks
  • Portable speakers
  • Cars ( please dont take apart a tesla :( they are too pretty)
  • Cameras
  • WalkiTalkies

While finding these other battery sources is easy i would defiantly recommend sticking to only looking for laptop batteries and they are the cheapest, have the highest quality brands, and the most cells within the battery.

Step 3: Getting Batteries Out

laptops typically use 12 volts as an operating voltage but a lithium cell can only provide and average of 3.7 volts meaning that most laptop manufactures arrange 3 batteries in series which creates one battery with a total voltage of 11.1 volts. But most laptops have 6 cells (for a longer run time) and still have a voltage of 11.1 volts. This is because the cells are divided into couples of 3, these couples are connected in parallel which keeps the voltages at 3.7 volts then the 3 couples are connected together in series to get a voltage of 11.1 volts. Anyway now that we know how they works lets get them out, most older laptops use a lithium ion cell called 18650 which is a very common battery type, some of the Tesla cars actually run on these batteries! The 18650 cells have a metal cylinder shape, they are pretty easy to get out of the battery case all you have to do is pull the casing apart and cut all the cables you can see, you'll see that all the cell are connected together with a thick flat metal connector, we need to slowly and carefully pull this off the battery taking care not to let any pieces of metal touch, if the metal refuses to peel off stop pulling and just cut the metal once this is done you should have a nice collection of batteries, just a heads up most newer and thinner laptops doesn't use 18650 cells because they are too thick so they use a lithium polymer cell if you find these you can use them in the same way as you would use the 18650 just be a bit more careful with them as they don't have any protection around them so its pretty easy to puncture them and cause an internal short circuit.

Step 4: Which Ones Are Dead

So now we've got the cells out of their casing and seperated them, this is where we are going to need a multimeter, over time some cells degrade, leak or rust which will result in a dead cell. Finding cells that have leaked or rusted are pretty easy just keep an eye out for discussing oozing batteries or rust however finding degraded cells isnt that easy, a cell may look perfectly healthy but is just completely dead, these are the degraded cells we find them by hooking them up to a multimeter and then put it on voltage mode, the positive probe goes to the postive terminal of the cell and the negative probe goes to the negative terminal. If the voltage is bellow 2.5 volts it means its kind of degraded but can still hold a charge, we are going to want to avoid them if possible however anything bellow 1 volt is completely dead and should be deposed of at a battery recycling facility. The ideal voltage you are looking for is between 3 and 4.2 Volts

Step 5: But Can They Hold a Charge?

Now we should end up with a group of cell that have a voltage between 3 and 4.2 volts but this doesnt mean its completly healthy as the cells may loose charge over time at a fast rate, to make sure this isnt happening charge the cells up to 4.2 volts, this can be done with a lithium charger the one im using has over charge protection meaning it will stop charging the cell when it gets to 4.2 volts which is really nice, once they are charged all the way to 4.2 volts leave them somewhere safe and check the voltage every couple of hours for a few days if the voltage drops significantly it means the cells cannot hold a charge and shouldnt be used. One of the cells I was testing started at 4.1 volts and dropped all the way to 3.6 volts over 2 days which was very bad.

Step 6: Working Cells!

Lo and behold we should now have a bunch of working lithium cells that can now be used for our projects! if you want to see a project where i used one of these salvaged cells to power a led photography and video light check out this instructable:

All the cell that rusted, leaked, degraded or could hold a charge should not just be thrown in the trash, they need to be taken to a battery recycling facility and deposed of properly .Thanks so much for reading, if anything wasn't clear please feel for to leave a comment or send me a message and ill try my best to get back to you!



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    45 Discussions

    Does anyone know which holders are best to use for these batteries?

    Or how to make them yourself?

    Is there anything I should think about when storing these cells in the workshop?

    1 reply

    i store mine in a 50 cal ammo can... dont know if that helps.

    I've removed 18650 cells from old laptop banks which registered 0V and they still charged and hold charge quite well (using them on powerful LED flashlights); they provide some 1500 mAh of charge, a lot less than their original spec for sure but still quite useful.

    4 replies

    I've done the Flashlight mod too.. Had a 19-LED flashlight, which had a slightly larger than "C" sized (almost as tall as a "D" Cell) 3x AAA holder, with the end-cap not fully tightened.. Surprisingly, you would think, 3X AAA would be 4.5V, should produce a bright light, but a single 18650 produces a Brilliant, borderline blinding light from this flashlight. (I imagine because of the higher Ah rate) Note above note, some get recharged up to 4.2V.

    This type of 3AAA flashlight uses the internal resistance of the cells to limit the current. Look at the battery voltage level drop when you switch it on.

    The Li-Ion cell has a much lower internal resistance, therefore can provide a higher current, even from a lower nominal voltage. (But it may burn out the LEDs quicker.)

    It is the fact that the li batteries have much smaller internal resistance. So a high current load makes the voltage drop a lot less.

    All of the 18650 cells that i've salvaged that had a voltage under 1 volt would not hold a charge but i guess some cells can come back from the dead and prove themselves useful, thanks for the comment!

    One must be careful to make sure that the battery that you are trying to charge is a "lithium-ion" battery. Those lithium "non-rechargeable" batteries can explode violently if you try to charge them. I know!

    Electrical fire extinguisher (also known as Class "C" in Australia Class "E")...

    Actually _no_ If a lithium cell is in the state of a thermal runaway, it is a Class "D" fire. A metal fire. Quote from wikipedia: "As with all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers (Class D type). Lithium is one of the few metals that react with nitrogen under normal conditions."
    Maybe you know about the fact that our Atmosphere contains ~78% nitrogen.

    But even a dry powder Class D extinguisher isn't the best option. Just use two metal buckets, or clay pods, both filled 1/2 with sand. If a cell gets hot, throw it in on of the buckets and fill it up with the sand from the other bucket.

    Just a quick note from someone who build a 1.5kWh battery from 18650s.


    1 year ago


    "couples of 3" this is fun, tho :D

    All good advice, but I have revived a few 18650 cells by tapping the ends with a higher DC voltage. I use a 9 VDC 0.3A (300 mA) supply, and I tap the ends several times then measure. If the reading is over 2 VDC, then I can use a standard Li-ion charger overnight and see if it hold the charge the next day

    Of six Panasonic cells that I recovered from an IBM ThiinkPad 600 laptop battery, four were revived.

    5 replies

    Did the same with the battery pack from an ancient Compaq NX5000. Saved all 6 of the cells that way. This sometimes works with Ni-MH batteries as well. In fact, the batteries I used to kick the Li-Ion batteries, were revived Ni-MH ones.

    This is HIGHLY not recommended. Overvoltage to a Lithium cell can cause it to explode. Especially going over 2x it's rated voltage. If you want to bring a dead cell back, use 4.2V for a LiCO (standard/common lithium cells), max! Or 3.9V if it's a LiFePo4 cell. Lithiums can't be de-dendrited like a Lead Acid battery can be. It takes a longer time to do so (if at all) as the dendrites are created differently and out of different material.

    You may have had fortune on your side from 4 cells, but it can quickly run out and ruin your day, and possibly house/garage/life.

    I have done "tapping" or jolting many times and not a single cell has even warmed up. Today I just did it twice! The current is too low to cause damage and the supply may warm up if the cell is shorted. But most bad cells are open and will not charge from a dedicated 4.2 VDC regulated supply (you can measure the current), so a "jolt" can kickstart the cell revival.

    I began this "tapping" on NiCad cells using a 15 VDC, 30 A battery charger. That generated many sparks but never an "explosion" or even a warm up. So 9 VDC is low enough to avoid damage and yet enough to "jolt" the cell.

    Just because you haven't had an issue yet, doesnt make it safe.
    Tapping a NiCd is completely different from lithium. NiCd charges charge like Lead Acid, higher than their run voltage. Lithium chargers on charge at the max rating viltage of the cell. For 18650s, thats 4.2v. Even 'tapping', your over charging.
    But, to each their own. I just hope you dont blow a cell. Good luck on your sparkies.

    Seems like a good idea. Note that since you are only "tapping" a few times it will not be overcharged. It is just a way to give a high intensity "jolt".

    Well!!! Well!!!

    I did before many years ago and I used 6V 6AMP Power Supply Charger, but the trick is that I have a special circuit and a chemical compound to effectively revive the chemical elements of the battery and restructure the ionic state of some batteries. It's only Chemistry and Physics, nothing complicated... But it's good that you teach others to search, look and get in other way their supplies's needs...

    GREAT JOB!!!

    I FORGOT TO MENTION: "NO EXPLOSION" We can control any kind of Energy with caution and previous calculation...

    For battery packs the use of a BMS (Battery Management System) can help with application for these types of batteries, and should be considered. It will protect cell voltage from dropping too far causing cell damage. The problem with cells salvaged from packs that even have a BMS is that if you don't know how long since the pack was last charged so self discharge could have taken the batteries very low or even flat. One specific problem to watch out for with these packs is that many BMS will take its power from the first cell of the pack, so in an unused pack it goes flat quicker than the other cells- you'll often find in recovered cells from old packs that the first cell is really bad- it's been in circuit trying to power the BMS while the other cells discharge naturally and more slowly.

    Smaller capacity battery packs should be charged with a charger that balances the cells, larger capacity are better off with a BMS fitted. Even a single cell battery can benefit from a BMS, and you can get (for example) individual 18650 cells with and without built in BMS's. I chose cells for my led torch with built in BMS's to protect the cells from becoming dead flat and avoid the possibility of cell damage.

    Battery packs which have a BMS will shut the pack down when it detects one (or more) low voltage batteries in a pack. It's a problem whether the pack is made up from (for example) 4S1P (4 cells in series with 1 parallel) or 4S2P (4 cells in series with 2 parallel), 4S4P etc.

    The cells in the batteries I use on my ebike are 15Ah, and are set up as 12S1P, one low voltage cell will shut the pack down before cell damage occurs from the voltage dropping too low, and will balance the cells in the pack charging the lower voltage cells to catch up with the higher voltage cells.

    I have also salvaged a lot of these and built an electronic load to test the charge that the cells could hold to determine which was still good and can maintain a useful capacity.

    Well done for the recycling!