Salvage!

Hey guys the place I work is doing some old electronics recycling that includes a bunch of old laptops so I have decided to salvage some cells out of the battery packs. I just started and already have about 14 18650s that I need to test and possibly condition. Does anyone have suggestions on the best ways to help these old cells get some new life back? I was thinking about getting a nice 4 bay intellicharger (nitecore) and just sitting them in there and watching the voltages, but if there are any chargers that have a conditioning mode I would be willing to pay a bit more to get one of those.

Any ideas?

Also if anyone is interested in buying some cheap salvage batteries let me know and I can put them up on the marketplace because I doubt I'm going to need about 106 18650s. They are all coming from Apple and Lenovo packs so Sanyo and Sony.

Any 18650 lithium ion charger would work. I'd just measure the voltage on them to see which ones are over 2.5v. I only think you'd have problems charging up the ones that had very low voltage with an off the shelf charger.

But perhaps the first step is just to get the lithium ion charger of your liking and then go from there if it won't charge up the cells that are very low. At any rate, I'd keep an eye on the ones that have been deeply discharged. There is always a little worry about lithium-ion from what I've read.

For the cells that are low, My route would be to hook them up to my programmable Agilent power supply and set the current limit low with a voltage at 4.20v and just see how they respond (ie: is the voltage rising) but not everyone will have one of those laying around or a cradle for the batteries either .

If you are messing with lithium ion cells like this you probably should have a voltmeter.

Test the batteries with a multi meter, if they are below 2.5v they might not be salvageable, but if they are around or over that you should be able to save them.
I recently recovered 15 out of 18 cells from two old ibm thinkpads, 3 of the cells were below 2v and would not take a charge, but the rest all working fine.

I used a Xtar wp2 charger, for the cells that were below 3v I charged them a bit at a time, like an hour or so, then let them stand for an hour then charged again, I did this until all the cells were charged up to around 4.2v.

It took a couple of days but it was worth it and all the cells are working great, they are better than the ultrafires that came with some of my recent purchases..

It's a great feeling when you turn on your lights with cells you've saved in this way.

Hope this helps and have fun..

With used cells, I recommend charging them in a very safe location. Preferably made of brick with no flammable items near by. If the cells are lower then 2.8v, I suggest just tossing it. Even if they take a charge they still have been over discharged and that makes their use very very risky. I'd hate to read that you or someone you sold cells to, had them installed in a light and it went hand grenade on you/them.
I have about 30 different cells I've salvaged and use in allot of projects but I err on the side of caution with these batteries. Any below 2.8v get immediately tossed.
All others are charged with my custom made cccv supply, with x.xxx volt meter as well as thermal protection/alarm. I only charge them in a small cement lined safebox that I drilled holes into for wiring and it's in a fairly safe location with ventilation in case of gas off.
Used and cheap cells are unpredictable, always use caution with them.
A standard charger should work just fine. Just make sure you follow the safety guidelines for charging lipo batteries.
GL with your project!

Let's bow our head in remembrance to the lost souls in this war (2V or less)

But the war was won and let's welcome home the survivors!

That's alotta soldiers! :twothumbs

What are you going to do with all these cells?

Well My plan is to charge and test each one then barring any issues I will strip and rewrap them with the brand and model number and use them for my lights, use some as giveaways maybe.

Acid303 said:

Test the batteries with a multi meter, if they are below 2.5v they might not be salvageable, but if they are around or over that you should be able to save them.

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One might say that's conventional wisdom. But I'm in the process of reviving 6 18650's from a new-old-stock laptop battery that were TOTALLY dead, and having 2nd thoughts on that. Probably the battery monitoring circuit drained them to 0.00V, and cells sat like that for a loooong time (months at least, possibly years). Yet I see one after the other coming back to life, first specimen looks to have good capacity left, and behavior is fairly consistent between cells. Also I've seen some manufacturer documentation suggesting that it may not be a problem when a battery arrives empty (that is: near 0V) at customer's location.

My gut says it may be comparable to how electrolytic capacitors behave when they haven't been used for years. Basically: charge & discharge regularly: no problem. Sit on the shelf for years, suddenly apply rated voltage, and there's a good chance it goes . I've seen this happen with 80's homecomputers, old power supplies, and CRT televisions. For some background, see for example here: Reforming Electrolytic Capacitors

So @ this point I'm more interested in the how & why, what happens exactly inside these cells. And judge cells on their history & behavior, rather than a quick voltage reading.

hiuintahs said:

I'd keep an eye on the ones that have been deeply discharged. There is always a little worry about lithium-ion from what I've read.

For the cells that are low, My route would be to hook them up to my programmable Agilent power supply and set the current limit low with a voltage at 4.20v and just see how they respond (ie: is the voltage rising)

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Indeed something like that may make more sense. My procedure so far:

1. Place in charger (which indicated "faulty" and wouldn't charge) to have 'em soak up a few mA's, and see if voltage continues to climb no matter how little. Only saw a few dozen mV's here...
2. Keep 'em in there until voltage hits ~2.0V. Capacity @ this point appeared practically nothing.
3. For cells where this took too long, a few 1-2 second 'jumpstarts' by short circuiting with a fully charged & known good 18650. Repeat with step 2.
4. After crossing into 2.0-2.5V, I could see they started to soak up charge. Brought them up to ~3.0V, took them out of the charger and just let them sit for a day. This gives the cell time to restore its electro-chemistry into normal operating state, while still at a relatively low voltage & state of charge. Voltage drops somewhat again, as expected.
5. First charge (only 2 cells so far). Lots of time spent around the 3.8V mark.
6. At least for the cells in this pack, it looks like once they hit 4.2V, they're good to go, and the only remaining question is capacity.
7. A couple of regular cycles (only did 1 so far), and repeat for the other cells. I wish I had some automated setup for that. And a flashlight is a pretty poor choice to give them a first run, if a cell decides to go at that point.

If you are messing with lithium ion cells like this you probably should have a voltmeter.

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Not "probably"... MUST.

Safely precharging an overdischarged Li-ion battery

Regarding charging overdischarged cells/packs, I recommend doing a web-search to examine the algorithms employed for such "precharging" by commercial chargers from reputable vendors. Below is a typical example, excerpted from p. 39 of the book: Y. Barsukov and J. Qian, Battery Power Management for Portable Devices, 2013. The authors are leading experts at Texas Instruments, responsible for the design of TI's impedance tracking fuel gauge algorithm - used in most laptop batteries.

When the voltage per cell is 2.9 V or less, charge use a charge current of C/10 rate or less. This is to provide recovery of the passivating layer, which might be dissolved after prolonged storage in the discharged state.

A low-rate charging also prevents overheating at 1C charge when previous overdischarge might have dissolved Cu from the anode current collector, which can cause shorted electrodes as a result of the Cu deposition. If voltage during low-rate charging does not increase above 3V after about 30 min, then a short is present. The charger should detect this condition by observing that the charge is below 3V and indicate a fault if the maximal time has been exceeded. Most chargers as well as battery gauges include a precharge timer that will ensure safe termination in such case.

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Re: Safely precharging an overdischarged Li-ion battery

When the voltage per cell is 2.9 V or less, charge use a charge current of C/10 rate or less. This is to provide recovery of the passivating layer, which might be dissolved after prolonged storage in the discharged state.

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Yep, that's very similar to electrolytic capacitors. Basically you have this thin layer that provides the ability to withstand voltage, that forms by itself when voltage is applied. But this re-forming takes much more time than a regular charge. oo:

So if long at ~0V, this layer may have dissolved. Apply full voltage quickly, and the cell may fail catastrophically. Feed it a small current so that voltage rises slowly, and this layer re-forms. After which you can charge as normal. Keyword being "slow" (as in: taking days)...

A low-rate charging also prevents overheating at 1C charge when previous overdischarge might have dissolved Cu from the anode current collector, which can cause shorted electrodes as a result of the Cu deposition.

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Internal shorts are a worry indeed. As state-of-charge increases, I think one of a few things may happen:

• Internal short(s) don't go away, and causes enough self discharge that you're unable to charge the cell further. Or
• Energy contents of the cell causes a large enough current to melt away such a local short-circuit. Or
• That local heating is big enough to trigger a thermal runaway event -> venting or worse.

Which makes me suspect that when you're able to reach full charge & the cell holds its voltage, things are probably okay.

As for my pack: all cells @ 4.0V or above now. Voltage steady, no excessive heating, and still soaking up charge. Looks like these cells turn out okay...

pimaxc said:

Well My plan is to charge and test each one then barring any issues I will strip and rewrap them...

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I thought for a second you were going to say "... and sell them as Ultrafires" :naughty:
Just pulled apart my first pack yesterday, haven't unsoldered them yet but some pairs seem down around 2.4V, some more like 2.8V, so maybe I can recover a few if not all.

So does anyone have a suggestion on a programmable DC power supply. Preferably with USB. Preferably cheap.

These are all of the cells that were able to be charged to their nominal voltage from 2V or more so I'm calling these my A stock.

Nice to see that you are recovering some cells. I've recovered quite a few cells also from old laptop packs but I would like to add some experience. I wouldn't go labeling all cells that charge to normal charging voltage Grade "A" until they are capacity (mAH) and internal resistance tested as well. I grade to A, B, and C. A is anything which has over 95% capacity left. B is 80%-95%. C is 60% to 80%. I recycle anything under 60% capacity. A good charger or benchtype power supply is a necessity for checking capacity. I love my antique HP 1970's power supply for this job.

I've recovered a bunch of cells that charged fine but were useless due to being worn out. Also for the cells with low voltages on them: I've never had a good Grade "A" cell after it has been below 1.5 volts for a while. Those highly discharged cells were always shorted, tended to short, puffed up if they were poly cells, or slowly discharged themselves. I've just learned to not bother trying to recover those below 1.5 volts anymore. The ones in the 1.5 to 2.5 volt range operate normally however if slowly trickle charged (less than C/10 rate) until about 3.2 volts or so like the above post specified.