Grinder battery not charging - any ideas?

Hey guys, my 18V Makita grinder battery stopped charging. It’s the 5.0Ah one. Plug it in, charger shows red light for a sec then nothing. Tried another battery, works fine. Any tips before I drop $80 on a new one?

Sounds like a dead cell. Have you tried jumping it with a fully charged battery? Quick 5-second zap sometimes wakes them up. Otherwise, the BMS might be fried. You could crack it open and check voltage on each cell. I’ve brought a couple back that way.

I had the same issue with a DeWalt. Try cleaning the terminals with rubbing alcohol. Also, leave it on the charger for an hour even if the light is off. Sometimes the slow wake up works. Or maybe freeze it? Nah, don’t do that.

Second the jump start. I use a car battery and some wire just touch + to + and - to - for 2 seconds. It can recover a deeply discharged pack. But be careful not to short it! After that, it should charge normal. If not, time to recycle.

Alright, I’ll try the jump start trick later. Cleaning didn’t help. Thanks for the advice, dudes. I’ll let you know if it works.