Capacity testing unprotected 18650's

[qumefox]

Can anyone recommend any relatively simple methods? I have about 36 non-protected samsung 18650's I scavenged today and I need to see if any of them are worth keeping or if they just need to go with the rest of the e-scrap.

 

[Gryphon]

36!? Ripping apart laptop batteries are we

Sorry, i dont know of any method for testing capacity.

 

[qumefox]

Yep. Hey, they were on their way to the recyclers anyway. I had a big pile of dell packs we picked up when we picked up escrap from a local company, and funny enough, all had LED charge indicators and all showed they were fully charged.

Actually I haven't scavenged them yet. I figured they were safer if I left the packs alone and intact until I actually started testing the batteries.

And actually I know a way.. Put a known load on them and see how long they take to run down. But since these are unprotected, that involves actively monitoring each one, voltage and temperature wise, for the duration of the testing... which is fine once or twice, but I don't really have time to do that 36 times.

*edit* Not sure how to edit thread titles, but I just figured out that all these are batteries are actually protected instead of unprotected. Samsung ICR18650-26A 2600mAh. So at least I feel slightly safer messing with them now, heh. And I should be able to capacity test them (still in a fireproof metal box though) without having to pretty much sit and stare at them.

 

[BShanahan14rulz]

Are they the light-green or teal color cells? They probably aren't protected from overdischarging, especially if they were harvested from a laptop battery pack. They do, however, have a safety vent so that in case of a catastrophic failure the cell will vent instead of explode.

 

[rockz]

You can get an idea from how the laptop pack was used. If its 2 years old or stored empty or used a lot in the laptop then most of the cells are junk probably. If you have a 18650 flashlight you can see how long it lasts until the light gets dim, but be aware of overdischarge.

I have a RC charger that I could test the cells for the price of postage, but I bet there's some nifty way out there.

 

[qumefox]

They're light pink. Like I said, they're samsung ICR18650-26A's, and according to the spec sheet for them they have overcharge, reverse charge, short circuit, and overcurrent protection and a 2.75v cutoff. I know they certainly have 'something' attached to the positive end of every cell but I haven't cut the shrinkwrap off one yet to see exactly what.

I took one of the packs apart today, every cell in it had 4.1v and I know they've been sitting in our office at least a year if not more, So none of these six I tested have a self discharge problem at least. But even if all 36 are bad, i'll still get my money's worth out of them.

*edit...again* Did more digging. They're indeed unprotected. Oh well. I'll still get my money's worth out of them regardless.

 

[qumefox]

Are they the light-green or teal color cells? They probably aren't protected from overdischarging, especially if they were harvested from a laptop battery pack. They do, however, have a safety vent so that in case of a catastrophic failure the cell will vent instead of explode.

After looking at one more closely, I think the vent is indeed what the structure on the positive end is. Thanks.

 

[BShanahan14rulz]

Even though they're unprotected, they are name-brand and should give you no troubles unless you intentionally abuse them. I used some pink-wrap Sanyos for a while until I found some teal Samsungs that performed much better. I charge in a wf-139 (or 138, I can't remember which...) and they all come out at around 4.21-4.23V, dropping down to 4.20 within a day. Haven't had time to do a controlled self-discharge test, but just from charging them all and measuring them a few days later, I can tell that these are better than my old (and I do mean old) sanyo's.

If you are really paranoid, you can buy some shrinkwrap and some protection circuits from the china sites and make your own proteted cells ;-) http://www.batteryjunction.com/prcimopfor3l.html

Often, good buck/boost flashlight drivers designed for single Li-ion cells will cut out at 2.6V anyways. You might consider that or just buying a protection circuit or two for use in your battery drainer with a known load.

Oh, and qume, have you seen about Basil Marceaux? He's got an official campaign video out now:
http://www.youtube.com/watch?v=fnx-SqMYknI

 

[qumefox]

I already started a PCB layout for a voltage cutoff circuit, timer and the load, which i'll pretty much be able to just plug a charged cell into and let run. I had already looked at those protection circuits. I may get a couple but it honestly depends on if any of these batteries are actually any good or not.

And i've seen that video before heh. Though that's two things I usually try to distance myself from. Rednecks and politicians.

 

[qumefox]

Well it took a while, but I finally weeded out all the ones with self discharge issues and I ended up with 72 18650's and 8 18500's. Next step.. finish coding my tester so I can capacity test them all to see how many are actually worth keeping.

 

[BShanahan14rulz]

Qume, I'd be interested in your results. You are somewhat local to me, well, more local than most. I was thinking of finding a way to test those 1300mAh WL cells to see how their voltage holds up under various high loads, but I'm really only curious, not curious enough to buy a CBA worth a few hundred bucks....