Thread: Dead 18650 batteries

Originally Posted by gadgetman

Protected cells will often fail when the circuit board dies or the battery voltage gets too low and the protection circuit will not allow them to recharge.

The unprotected cell itself has a 'one time' protection switch under the button cap end that will trip if current gets too high and the cell gets too hot. As a rule once this happens you should bin them. If the switch is reset they often get really hot when you try to recharge them which is not good with such a reactive element as Lithium. Check the voltage across the cell. If it is zero and has open circuit resistance then the switch will have gone. If the voltage is below 3V they are generally gone, though I have recovered some from 2.5V they hold very little charge.

Anything I can do to stop killing the rest? The ones that are still running are fine. Hold good charge and last. Hard to understand what’s the cause.