18650 testing Q.

[alpg88]

hey guys,
i have about 50 18650 salvaged from old and not so old laptop batteries, most are not crappy made in china cells, but in fact made in japan, they are all in different shape i assume, some are at the end of their lives, some are still pretty strong, since i use different cells in lights that i used 18650 before i don't need that many cells, especially dying ones.
so my Q is how do i test condition of those cells, how much capacity left, so i can only keep the ones that are still strong???
is there analyzers on sale? or chargers that will do that, or there is an easier simpler way??? obviously price matters, i wont spend $ on test equipment if the same money will buy me dozen of new cells.

 

[^Gurthang]

Alp,

I've used recycled laptop cells w/o problem. I pull the cells and check the existing voltage. If any cells test <3V I toss them.

I use a "resurrection" charger on the cells in the >3.5 V category [charger is 3.6V / 100 mA from a wall-wart supply]. I charge on a timer for an hour and check voltage and cell temp. If nothing is awry I repeat until I hit >3.6V [the charger will top out at about 3.7x V. I let the cell rest and check the voltage for self-discharge over a few days.

If the cell holds then I'll put it in the "2nd life" charger [another wall-wart supply 4V / 150 mA] and get the cell to ~ 4V. Again, let it rest and check for self-discharge.

Once the cells pass this test I charge them fully and run them in a light for 1 hour. If they hold V above 3.7 I put them in a storage case.

Some will scream and run away when they read this. I do all my charging in a fireproof lab area w/ LOTS of ventilation. I have yet to have a cell that passed stage 2 fail or do something nasty. It MAY happen one day but not thus far.

 

[etc]

I throw cells that read below about 2.5-3V.

I throw cells away that get hot. Actually I charge them and put them in the one-time-use category. Meaning that I use them once and toss them, don't charge them again.

The rest I label with voltage. If a cell doesn't hold at least 4.1V, I throw it away also. I have a lot that get the full 4.2V and some that are 4.1V. I use 4.1V for EDC but have a backup of premium cells like Panasonic 2900 mAh cell, which in turn are backed up by CR123A cells.

 

[alpg88]

well in that case I'll keep all of them, when i took packs apart, i kept only those that had at least 3,6v. i had to toss about 100+ cells that were below 3,6v.
what I'd like to know is how much capacity left in them. if it is at all possible.

 

[jasonck08]

most salvaged cells that I've taken from laptop battery packs are rubbish and hold around 1/2 their rated capacity and voltage sags a ton.

I've gotten lucky a couple times and pulled some 2400mAh Samsungs that still held a good 2200mAh charge.