why would a 16340 li-ion get charged to 4.7V?

Batteries and Chargers Chargers
1

why would a 16340 li-ion get charged to 4.7V?

i have a liitokala charger, 3-4 years old

trying to charge an old 16340 cell, which was low quality and is now old ish
it has been used a lot though probably not over 100 cycles

i set the charge current to 300 ma, or 500 ma
true capacity is probably about 100 to 200 mah

after it is done, the open circuit voltage is about 4.7V

not sure how or why it does that?
wouldn’t it stop charging when terminal voltage gets to 4.20?
or would an old cell continue to rise in voltage even after the charge is done…?

how can it get tricked like that, or is it just the old cheap worn out battery, misbehaving

if you try to stick that one back in [to discharge it or test it], the charger says NULL - i guess because it thinks this can;t be a legit battery
i can stick it in a flashlight, run it a few minutes, then voltage will be back under 4.2, then it will charge, but not when it is at 4.7V

??

wle

2

How are you measuring the voltage?

If you are using a multimeter, is the multimeter’s battery fully charged?

3

yes - DMM reads 4.2 on a normal 18650 at the end of charge, or later…

wle

4

There is a possibility that the cell has such high internal resistance on a CV charge that it hugely jumps in voltage in that phase, and the charger doesn’t cut off quickly enough.

I’ve literally only had one salvaged 18650 out of hundreds that had this. But by cycling it at low currents and super slow charging it, it recovered.

TLDR: Your 16340 is dead.

5

Recycle it carefully, don’t contribute to garbage truck fires.