Got a couple-year-old pair of “DE” brand (discontinued from Rat Shack, www.deworld.com on the cell itself) 26650 cells. One is fine, held 3.65V, although that may be the one I used to test my L2 and recharged at some point. The other probably has a tripped protection circuit. Only registers a fractional-volt on the meter, doesn’t seem to take a charge at all, hasn’t burst into flames (yet) after being drained, so I want to take a crack at resurrecting it if possible.
I read a thread on CPF about jolting the protection circuit to jumpstart it, and the voltage is slooooowly rising while it’s still in the charger (1.5ish V so far). I still have it cooking, so that might rise some more.
Anyway, if the protection circuit still gets in the way, I’ll be tempted to just skin the cell, pop off the circuit, and play with the nekkid cell to see if it takes a charge. If not, out it goes, but if I can salvage it even for temporary use, that’ll satisfy the cheapskate in me.
I know that protection circuits always present a parasitic drain on unused cells, which is why I’m always having to recharge my protected panny-Bs every now and then, while other unprotected cells keep their charge, well, a long time. Kinda sucks that just keeping those 26650s around unused might’ve killed one of them. Kinda ironic, too.
Ideas? I imagine they’re also double-wrapped, too, so I’d only have to skin the outermost layer, no?
Uhmmmm, would it help if I told you this is a really bad idea? Once a cell has been discharged to this point it is dangerous to try and charge it. They can and have gone into thermal runaway and they will do some amazingly dangerous things. For your own peace of mind take it to your local big box store and ask them where they have battery recycling and throw it in the bin. Wrapped with tape or some such.
I’ve had that issue with a couple of batteries before. One of them was dead on arrival, wouldn’t even register on the volt meter. I took a known good battery and the bad battery, put them positive to positive and jumped them with a wire on each negative. This worked on both batteries, even the doa one. They are both still going strong and I have no issues with them. Just make sure you charge the bad battery as slowly as you can.
This depends on the situation. What voltage does the cell read? If protection has kicked in it may read 1.8-2.0 volts? Once you get some charge into the cells they will gain capacity and jump up voltage.
If you have a dumb charger use that because that will force current into the cell while a smart charger may not.
any recommendations for brand and model for a dumb charger? I have several dead li-ion batteries harvested from a defective xiaomi powerbank, only few of them are working.
That’s just it, it hadn’t even been used even once. I’m only trickle-charging it to see if the protection circuit would just get out of the way and let me see how the cell itself is.
Again, worst case, I’ll just pull the circuit and let the nekkid cell try to charge… sloooowly.
Yep, that’s the trick I saw on CPF and tried. And jolting it with (current-regulated) 12V from a wall-wart.
Will see how it goes…
Oh yeah, I’m using a 2buk charger from FT. I keep a few of them around, 1-2 in my bag, etc., they’re so useful. Lotta people here hate them because they’re so sloooow, but I’m usually not in any particular rush, so I let a cell top off while I’m at work, or overnight, etc.
It doesn’t quite read anything yet, because I’d be measuring through the protection circuit. Still isn’t drawing enough to glow red (charging), but green (ready), just as if the charger’s plugged in with no cell in the holder.
The charger may actually have some smarts, but I’m not quite sure how much. Charging ICs (Maxim, TI, etc.) are cheap yet can do pretty smart things.
From a powerbank (or laptop battery, etc.), you’re likely to get unprotected cells. If they’re not registering, that pretty much means they’re good’n’dead. That, I’d be careful trying to resurrect any.
In my case, the cell is protected, and its voltage can be in that limbo area that the protection circuit kicks in and keeps the cell disconnected from the outside world. Ie, nothing in, nothing out.
That’s why I’m willing to just pull the circuit completely to get it out of the way, and then try playing with the nekkid cell (which if too low will go into the bin anyway).
Thank you lightbringer for the safety precaution. well, for a 16000mAh powerbank it’s just 4 dead cells and 1 working cell. those 4 unprotected harvested cells are good for disposal and not worth the risk. Cheers!
i bought those same “deworld” pack of 2x26650 at rat shack on clearance… also a 2 pack of 14500s, and a 2 pack of what i thought would fit in my cr123 tiny light.
my 26650s were fine… the 14500s??? one was having “issues” like yours. I tore the outer wrapper off and took the protection circuit off… charged up and worked perfect after that.
i have honestly never ever had any problems using unprotected batteries, ever. Several “protection” circuits have been tore off and it usually “fixes” the cell.
i dont have much use for protected, that i can see.
i had a deworld 26650 that was dead when i got it.and it was a dead shorted cell.
these are cheap cells and should be recycled at the first sign of a problem.
If the cells stays a while below 2.5V the low voltage cnt keep the electrolythe from eating up copper and copper crystals are build up on other parts of the cell
If you charge the cell the interior expands always a little, thos copper crystaly can punch through the insulator and you got a firecracker in your tube flashlight
Its a really bad idea trying to ressurect long time oberdischarged cells, many of the accidents with exploding lithium cells are caused by such cells
Stick a needle between the pcb and the cell and measure the voltage. If the cell is ok, throw out the pcb. If not, try applying some amps directly to the cell.
I have a few of these DE cells. Only 3500 mAh, but they perform decently.
The tail side protection circuit has been removed on all of mine, but I kept the +button and simply shrunk new wrappers on them. Unprotected they are a nice size for Convoy L2/L6s and other cell-fussy lights.
The stock wrapper is a kind of thin sticker, easy to peel off. Underneath that is the typical +feed strip to the protection circuit, isolated with kapton tape from the cell casing. Be very careful when removing this strip, easy to do a short-circuit.
Of course, if they measure low upstream of the protection circuit the only option is recycling.
Think that’s what I’m going to do when I go home, just skin it and cook it, just like a squirrel.
And I forgot to add that I do use protected cells for any app where they can accidentally get bumped on. I have quite a few with no µC, just a few 7135s, so while the 7135s should turn off at some point from low voltage, I don’t want to have to rely on that. Certainly not if its cutoff is 1.X volts.
Well, that kinda describes almost anything sold by RS in its later years, so…
Back when they were the kings of rebranding, you could get rebadged Energizers (same mfr location in fine-print!), but when they just went with 3rd-party free-for-alls, that all changed.
No idea who or what “Digital Energy” is all about, so they might as well call it DigitalFire for all I know.
