Help! My drill's battery won't charge anymore

Hey all, I've got a DeWalt 20V drill that's been great for a couple years, but now the battery won't charge. I plug it in, the charger light stays red, and after a few hours it just blinks red/green. I've tried cleaning the contacts, but no luck. Any ideas?

Had the same thing happen to my 20V max. If cleaning didn't work, it might be a dead cell in the pack. Check the voltage with a multimeter - if it's below like 14V, it's likely toast. Sometimes you can revive it with a jump start, but honestly for the price of a new battery, it might not be worth the hassle. Also, check if it's still under warranty - Dewalt's warranty covers batteries for 3 years.

Yeah, that blinking red/green usually means the charger detects a bad battery. But before you trash it, try leaving it on the charger for a full 24h sometimes it balances out. If not, you can try the ol' trick of putting it on a freezer (after wrapping in a bag) for a night, then let it warm up and try charging. Works occasionally if it's a lithium pack. Never worked for me though.

Also check the charger itself - I had a charger go bad and it acted exactly like that. Try charging a known good battery on the same charger. If it works, it's the battery. If not, it's the charger. Also, if you've got a newer charger with a USB port, sometimes the port gets dirty and messes with the sensing. But Carl's right - if it's a few years old and used daily, it might just be time for a new battery. They do wear out eventually.

Thanks all! I'll try the multimeter and see if it's under 14V. Also good tip on testing another battery in the charger. Yeah, I beat the crap out of this one so probably just replace it. Appreciate the help!