My drill's battery won't charge - any ideas?

Hey guys, my 18V Makita drill battery has been acting up. It was working fine yesterday, but today it won't charge. The charger light stays red and blinks. I've tried different outlets and even cleaned the contacts. Any suggestions?

Larry, that blinking red light usually indicates a battery issue. Could be a dead cell or the BMS (battery management system) tripped. Try leaving it on the charger for an hour - sometimes it resets. If not, you might need to crack it open and check individual cells. Had an old Dewalt pack do that; I replaced two cells and it works like new.

I'm with Chris on the dead cell possibility. Also check if the charger itself is good - try borrowing a buddy's charger. I've seen chargers go bad more often than batteries. But if it's the battery, don't mess with it unless you're comfortable with lithium cells. They can be dangerous. Sometimes it's cheaper to just buy a new one on sale.

Hold up, before you open it, measure voltage at the battery terminals with a multimeter. Should be around 18V. If it's way low, like 10V, the BMS has likely shut it down to prevent damage. Some chargers won't charge a deeply discharged battery. You can try 'jump starting' it with another charged battery (in parallel briefly) just to bring voltage up. Done it many times. But be careful not to short anything.

Thanks guys! I'll try the jump start trick first. I've got a multimeter so I'll check voltage. If that doesn't work, I might just get a new one - not worth burning the house down haha. Appreciate the help!