Threw away $30 on Laptop batteries...

[WarHawk-AVG]

@eas

I wouldn’t pitch any of the >=1.9v cells yet.
I’d give each one 50-100mA for a couple of minutes. If the voltage rises to ~3v in that time, I’d set them aside over night and check them the next morning. If they still are close to 3v, I’d charge them fully at 200mA (each), checking a few times in the first 30 minutes. Any that warm up noticeably, I’d pitch. Any that don’t reach termination in a reasonable amount of time, I’d pitch. Any that drop below 4.15 or so overnight, I’d pitch. Then I’d discharge test them. Any that had enough capacity to be interesting, I’d charge again at a normal rate, again checking for heating.

I’ve been experimenting with new-old-stock and used laptop pulls for the past few months. Even so, I’d say my knowledge is pretty limited and provisional, given all the variables, etc.

With that said, I’ve had great results with new old stock laptop pack pulls that were as low as 2v.
I haven’t done much with any ~2v cells from used packs because the wide range of packs I’ve looked at either have cells closer to 3v, or below 1.5v (some in the negative/reversed-polarity).
I have put a few cells that came out at ~2.8v through 20-80 cycles. I thought they’d decline quickly, since they were already down to 2/3rds of nominial capacity, but they’ve held up quite well.

My reasoning for why I think the the >=1.9v cells are safe for further testing: The ~2.75 low-voltage cut-off limits are for cells under load, where there is a chance of overshoot, so they have a healthy safety margin built in. Battery University suggests that cells that have spent more than 1 week below 1.5v are a risk of partial shorts due to formation of metallic copper structures. I figure that ~2v is above the BatteryU guideline. Further, I figure that laptop packs are protected, and so never dipped below the manufacturer provided discharge limits while under load, if their voltage is low, they came to it gradually, through self-discharge.

As an added safety measure, using low current in the initial pre-charge and charge means that the cell won’t have much energy in it if there is a partial short, and so is unlikely to go into thermal runaway before the short is detected. Checking for self-discharge after the precharge to 3v is a chance to check for partial shorts early.

Thats my thinking, what people do with it is up to them. If people want to pick it apart, thats great, we all might learn something.

Yeah for some reason those batteries that sit idle and static for a long time seem to “go to sleep” even if they get below safe levels….and a slow waking up brings em back most of the way…funny how that works

Just make sure they DO NOT HEAT UP when charging at .5-1A…warm is ok…almost too hot to touch is not safe!

Low and slow until they come back up to operational voltage

Great info here guys!!!