Hi there,
I recently pulled some Samsung ICR18650-26C cells from a used laptop battery pack. Some of them read 2.2 volts, some of them read 2.3 volts. I understand that this is fairly low for 18650 cells. What is your recommendation on what to do with these batteries?
I ordered an Opus BT-C3100 V2.2 - is it safe to charge the batteries at 200mA and see what happens?
Edit: I also have a decent multimeter available.
Yes
those are probably ok.
watch for heat while charging.get used to how much heat the charger contributes so you have a good reference when charging ones you need to check for heating.only ones i have had heat up when bad have been old red sanyo’s
Thanks for the information. I ordered four Sanyo NCR18650GA cells together with my charger. I’ll charge those first to see what is normal. Do you have any idea what capacity I should expect? The laptop pulls are rated for 2600 mAh, but I have no idea how much the cells have degraded.
only way to know is a discharge test.i do my grading test at 1a
Yes, do a discharge test with the Opus to make sure.
Above 2.0v is still ok to recharge. Below 2.0v should be trashed.
Thanks for sending that thread. I read elsewhere that you should trash laptop pulls if they’re below 2.5 volt. Any idea why that would be recommended?
That’s quite serious. Can this occur above 2 volts?
Read ThisThread and you’ll better understand LiIon’s. When charging laptop pulls for the first time you should monitor the cell temperature closely and often, and the same goes for the discharge test. If all seems well after a few uses then you’re not likely to have problems. Any of those cells which gets appreciably warmer than it’s pack-mates should be recycled.
Phil
Welcome to BLF ZAREX95!! Glad to have you here and a great question!
I would charge them in spurts. On the opus, give them 200 or 300ma charge to get them to 3.0v while watching the voltage rise. Take them out and let them rest for 30 minutes. Are they at or above 3.0 volts? Yes? Continue. If below 2.9-3.0 volts or getting very warm I would toss them in a bucket of saltwater for a few days, there self discharging, not good and dangerous. Do it again charging them to 3.5 volts at 500ma following the same instructions as above, then again to 4.2 volts letting them rest 30 minutes in between charges. This will also help you find cells that are not behaving like the others and could be bad while charging them using this method. This is the way I would do it if they were my cells.
Let us know how it goes.
I started the charge process before I read your message. I charged them to about 3.6 volts @ 200mA while checking the temperature every few minutes - I was working with my charger right next to me. The batteries remained very cool, barely getting warm to the touch. I took them out of the charger when I went to bed. Overnight the voltage did not drop. I pulled eight cells from the battery pack, I’ll follow this process for them when the first set finishes charging.
I measured the internal resistance every now and then. It dropped from 400-550 to 170-190. Note that at the last value the batteries weren’t fully charged yet. Does this say anything about the health of my cells?
I charged the cells to 4.2 volts last evening, and they are still at 4.2 volts eight hours later. The internal resistance measurement dropped to about 100-116 mOhm. I just read in the manual that there is about 30mOhm contact resistance, which should be substracted from the measured value. This brings the internal resistance down to 70-86 mOhm. I did some reading and this value seems to be quite nice.
I just started a discharge test to measure the capacity.
I think so.
that ir is decent for laptop pulls.
> I took them out of the charger when I went to bed.
When you aren’t really certain what’s inside the outside wrapper
(“do you feel lucky?”)
it’s always conservative to
— do the charging outdoors on a fireproof surface.
— understand when not to inhale.
Especially if you have family indoors.
Yes, and it often does eg. during over-charging.