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

Hey everyone, I've got a DeWalt 20V drill that's only a year old. The battery suddenly won't charge – the charger light just blinks red and green. I've tried other batteries and they charge fine, so it's just this one. Any ideas what's wrong? It's been sitting in my garage for a few weeks, but it was working before.

That blinking red/green usually means a bad cell in the battery pack. Since it's been sitting, maybe it discharged too low and one of the cells went below the safe voltage. Is there any chance you can check the voltage with a multimeter? If it's like below 10V, the charger might not even recognize it.

Hey Sarah! I've had this happen with my old NiCd batteries, but these Li-ion ones are picky. If the battery's been dead for a while, sometimes you can 'jump start' it by putting it in parallel with a good battery for a few seconds – but be careful! I've seen videos on YouTube. You just connect + to + and - to - for like 10 seconds, then put it on the charger. Might be worth a try.

Whoa, hold on Larry! That's risky advice. Jump starting a Li-ion pack can be dangerous if you don't know what you're doing – could damage the battery or worse. Sarah, if it's under warranty, I'd just contact DeWalt. They've got a 3-year warranty on batteries. If not, replacing the battery is probably the safest bet. Don't mess with it if you're not experienced.

Thanks for the replies. I checked the voltage and it's reading 0 volts, so I think it's dead as a doornail. It's out of warranty, but I'd rather not risk blowing up. I'll just buy a new one. Appreciate the help, though. Might look into that repair kit from WrenchWendy's suggestion if I feel adventurous later.