Introduction: Salvaging Rechargeables for Projects

Picture of Salvaging Rechargeables for Projects

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

Picture of 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

Picture of 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

Picture of 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

Picture of 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?

Picture of 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!

Picture of 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!


AugustV2 (author)2017-07-11

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

Or how to make them yourself?

MartinB125 (author)2017-05-29

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

snakieee (author)MartinB1252017-05-29

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

carlos66ba (author)2017-05-23

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.

Gelfling6 (author)carlos66ba2017-05-24

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.

ElectroFrank (author)Gelfling62017-05-29

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.)

carlos66ba (author)Gelfling62017-05-25

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!

Joe Byers (author)2017-05-29

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!

tschaerni (author)2017-05-28

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.

leo00 (author)2017-05-26


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

RaymondR6 (author)2017-05-25

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.

Athelas (author)RaymondR62017-05-26

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.

Korishan (author)RaymondR62017-05-25

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.

RaymondR6 (author)Korishan2017-05-25

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.

Korishan (author)RaymondR62017-05-25

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.

carlos66ba (author)RaymondR62017-05-25

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...


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

AlanS14 (author)2017-05-25

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.

Teratron (author)2017-05-24

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!

pohair (author)Teratron2017-05-25

How about sharing the design & build of that electronic load?

i would highly recommend this one, its the one ive began to use

Teratron (author)pohair2017-05-25

Hi, there are several online from China like these:

Mine is similiar this this one:

But I just use a voltage follower op-amp to drive a fat MOSFET on a big heatsink to act as the "electronic resistor" with a feedback circuit on a current sense. Then you can use a Volt/Amp display to indicate voltage/current that appears on the 'load'. There are lots of designs, Google is your friend. ;-)

Gelfling6 (author)2017-05-24

Someone, on Youtube, mentioned that some dead cells, you can revive, by CAREFULLY inserting a small, thin, and blunt object in below the vent holes of the + side, and applying slight pressure down.. Now, this is a tricky, if not DANGEROUS method, but it does work.. Apparently, cells which have become over-heated, vented, or developed a build-up of the electrolyte turned crystal, between the vent and the - side of the cell.. They mentioned some have an inner-shell, that becomes disconnected by either over-heat or, crystallized electrolyte, and refuses to re-seal, or 'reset'.. I've been able to recover about 98% of about 42 18650 cells this way.. the 2%, apparently I pushed too hard, and in doing so, reset, yes, but also punctured the seal. BAD!! result, when I recharged the batteries, they produced a liquid of the electrolyte, which formed on top of the cell just outside the vent.. Dispose of these properly as mentioned! (not just throw away, but safe disposal. The electrolyte is an alkali, and can cause chemical burns.)

Korishan (author)Gelfling62017-05-25

For safety reasons, I would not recommend this method. Definitely dispose of them, as you mention.

However, a cell that is below 1V can be revived, and potentially have nothing wrong with it. Put it in parallel with a good cell and start charging. The two cells will start balancing with each other. When the lower voltage one goes above 2.5V or 3V, then you can start charging it independently. we talk 98% recovering lithium cells from laptop batteries or powertool packs. Loads of information regarding this specific topic.

Thanks for the info and helping to spread the reusability of lithium cells

polofsson (author)Korishan2017-05-25

No, do not short your good battery to your bad one, and in doing so create a fire hazard or possibly ruin one cell more...

I mean, you can try to revive dead cells, they wont be good for heavy duty applications any more but might still get some use. Just use a current limited charger/power supply instead. Such as a lab power supply, you can get one cheap and very useful for other things also.

RigoC (author)polofsson2017-05-25

That's not what he said. How would there be fire hazard? In parallel, it's just a drain on the working battery. It's balancing. If the other one is dead, again no hazard.

dhafenstein (author)RigoC2017-05-25

Actually, placing a bad cell in parallel with a good one is dumping energy from the good cell into the bad one with no current limiting other than the internal resistance of the cell. This can damage the good cell because the discharge rate is potentially very high, and it can result in excessive heat generation in both the discharging and dead cell. It can result in a fire hazard if either cell goes into thermal runaway.

It is far safer, and better, to use current and thermal limited charging of lithium ion batteries. Most battery packs, especially for laptops, include thermistors attached to the cells to provide temperature information to a charge controller in the pack, or at least bring that out to pins on the connector to allow an external charger to control the charge current. As the temperature increases, the charge current should be decreased.

Korishan (author)dhafenstein2017-05-25

You will only damage the good cell if the bad cell is shorted. Which means it has 0.000V and connecting another cell to it will immediately start heating it up. If a cell has some voltage, it's not shorted and will not damage the good cell.

The is a balancing trick used by powerwallers. It is a timed tested, replicable, and 100's if not 1000's of successful charging.

It's easy to determine if a cell is shorted by doing a continuity test. The resistance should be around 36mOhms. Safe cells can go as high as around 100mOhms. Higher than that, you'd want to keep them as individuals for flashlights and such.

Korishan (author)RigoC2017-05-25

Agreed. We do it all the time when building our powerwalls. A lot of <1V cells will be considered 'dead'. However, they can be revived with the method I mentioned and they will perform as almost as new (not guaranteed). The reason for paralleling them is allow the low voltage to be charged by the charger; and to allow for a super controlled low mA charging of the dead cell. The good cell will take most of the mA, will the weak one will take minimal. However, it will gradually increase until it can be charged on its own.

It is FAR safer than putting a foreign object under the cap and pressing down on the inside of the cell. That could potentially cause a fire; as the electrolyte is the explosive part of a lithium battery.

dhafenstein (author)Korishan2017-05-25

I dont understand how putting the good cell in parallel with the bad one, and charging them as a pair does anything. As you pointed out, the bad cell will draw most of the current. The current limiting is performed by the charger. The good cell voltage will not rise until the bad cell voltage rises, meaning that it is beginning to charge. So, placing the bad cell on the charger is essentially all that is happening here. The good cell is basically along for the ride and gets whatever current is not used by the bad cell.

Korishan (author)dhafenstein2017-05-25

Ok, I see you haven't looked at the datasheet for lithium chargers. They won't charge a cell that is below a certain voltage. It varies from charger to charger, depending on the root chip. The TP4056 wont charge a cell below 1.2V, I think. Might be 1.6V, I dont remember. So, if a cell is below 1V, the charger wont even turn on to begin with. That is why you use another cell in parallel to bring the average voltage up so the charger will kick on. And, you monitor it for awhile watching for when the voltage comes above 2V. Then you can take them out of parallel mode and charge the low cell separately normally. This will safely revive a low voltage/dead cell. This can work even with cells that are essentially below 0.1V, as well. It has been done and proven it works.

However, it must be noted, why is the cell that low to begin with. Did it self discharge to that level, or was it brought that low through usage. Most likely a laptop cell will have self discharged, but it is possible to have been brought down by a bad cell in the pack, or a failed charge controller in the pack and let the whole pack drop way lower than was intended.

If the cell was depleted through self discharge, then the quality of that cell will still have lot of life left in it and may have greater than 70% of life and amphours left. On diypowerwalls, we've come across cells that were <1V, revived them, and they came back to a capacity of 80% of their rated amphour; which, btw, is amazing!

There were some on the forum that almost threw their cells out because they didn't know. They did the above method, retested the cells, and almost doubled their available cells for their powerwall applications.

Gelfling6 (author)Gelfling62017-05-24

Also, remember, Most chargers for these batteries, will charge them to 4.2 Volts (+/- .02).. If you plan on using them for projects which have a top voltage of 3.9 (I've safely run a few per the datasheets said 3.6 was maximum, at about 3.8V without problem, But....) worse case, always add a Lx117-33 (examples L1117-33, L8117L33) low-dropout regulator, just to be safe!

crickleymal (author)2017-05-25

I would also run them down using a load in order to determine the capacity.

im waiting for a constandt current device to arrive from chine and then i will be testing the capacity

efoster6 (author)2017-05-25

I have "salvaged" some batteries from a rechargeable drill and after destroying said battery to salvage said batteries I noticed that all that was wrong was a tab had lifted and broke the circuit so no go and no charge :(

im so sorry to hear that!

datamanlv (author)2017-05-25

Small typo; ...just keep an eye out for discussing oozing batteries or rust... I think you meant disgusting oozing batteries.

yup :D, thanks for pointing it out

larrylw (author)2017-05-25

I brought back a couple of Lipolomer rechargeable flat batteries from an old DVD player that read less than 1v and were made in 2005 and not used since then. I bought a charger from Bangood for about $30 and charged it until finished. The charged quickly dropped down to 3.5 or less, So every day for a weak I recharged them until after a week or so they now hold a charge at full voltage.

RaymondR6 (author)2017-05-25

A third note: many smartphone use flat Li-ion cells that have a protection circuit in them. The top plastic cap may have three or more contacts where only two are for power and the others are for temperature sensors to detect heat These also have overvoltage and overcurrent protection chips inside, so there are tiny FET switches and a fuse in that circuit. If you measure zero volts, then the fuse or a FET is open. The cell cannot be reused in a smartphone.

But if you are willing to experiment and take a risk, then remove the packing and the plastic caps. The protection circuit is on the negative electrode of the cell and the metal body is the positive. There is a small metal strap electrode that carries that side to the circuit. Removing the cap and disconnecting the electrodes from the circuit allow you to measure the cell directly (be careful as the entire metal body is the positive!). If it has a voltage, then use alligator clips to charge and remeasure. If it does hold a good charge, you may find a use for this cell later. But if nothing happens, just have it recycled.

RaymondR6 (author)2017-05-25

As an additional note, there may not be any known recycling center near your home, but you may ask battery sellers. I have one nearby (Batteries Plus) that will take in any type, rechargeable or disposable, and handle them for recycling. I give them all the lead-acid batteries from my UPS equipment, too.

der_fisherman (author)2017-05-25

Good common sense.

Thanks for sharing


tallbob (author)2017-05-25

Note: while your image shows a 2032 cell and says it isn't rechargeable, you can in fact get rechargeable Li-ion versions of these cells. They are rare, though.

AlFXlogic (author)2017-05-25

I wish I were like you when I was 18, keep it up!

About This Instructable




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