I have a Hitachi 18V li-ion drill with 2 bats. One is fine, the other won't take a charge. After about 30 seconds on charge the charger goes from steady light to flashing, indicating its charged. Checking the output voltage, it is down at 3.86v, the other is a tad over 20v.
There arnt any wires loose in the battery as far as I can see. Is there anything I can do with this? There looks like there are lots of fuses/regulators etc wired into the batteries, and I cant check individual batteries as its all sealed in.