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.

how longs it been stored flat ? liions dont like to be stored without use for terribly long…..

There’s a fairly common issue with makita batteries where they wont take a charge if the voltage is too low. It can happen in the cold or if you leave them sitting for ages. The fix is to jump start them from another battery just to raise the voltage a little. 3.86v might be a little low for a jump though. You could make a trickle charger from a power supply but you’ll need to keep an eye on it and stop when the voltage rises to a reasonable figure then try it on the proper charger.

Battery is most likely dead. I had a similar issue with my snap on drill with 3 batteries. Put them on charge and the light would indicate they had been charged fully in a few minutes.

It’s the cells inside the battery that go.

I got them re-celled at batteriesplus. Very reasonable cost £25 each instead of £90 for a new battery from snap on.

Didn’t think it had been stored flat, however, maybe I did…

Jump starting, by this, do you mean wiring the other bat in parallel, + to +, – to -, and stand clear for a few mins?

Its a a four cell battery, I’ve had it apart to see if there was anything obvious, to no avail.

You need to be careful messing with Li-ons, they can go pop easily, especially if the regulator/electrickery gives up. If you are going to mess about with a different power supply, do it outside and keep clear!

So, charge, stand clear, and shock!

Maybe send it off for a refurb.

Cheers

Thanks for the advice nickjb, jump started, voltage up to 16v after jump, popped it on charge and it seams fine. Yet to see if its lost much capacity.