My drill's battery won't charge - help!

Hey all, my 18V drill battery just stopped charging. Plugged it in, charger light flashes red, nothing else. Tried a different battery and that charges fine. Any ideas what's wrong? It's about 2 years old, used daily.

Sounds like the battery might be toast. Had the same thing happen with my old one. Sometimes the cells just give up. You could try a trick: put it in the fridge for a while? Nah just kidding. But seriously, if it's under warranty, check that. Otherwise, might be cheaper to buy a new one than to try to fix it.

Before you buy a new one, check the contacts on the battery and charger. Sometimes they get dirty or bent, and that causes a bad connection. Clean them with a bit of rubbing alcohol and a cotton swab. Also, check if the charger has a reset button or something. Some chargers need to be unplugged for a bit.

Also, look at the battery's voltage with a multimeter if you can. If it's way low, it might be dead. But if it's still holding some charge, the issue might be the charger's detection circuit. Another thing: make sure the battery isn't too hot or too cold. Extreme temps can prevent charging. Let it sit at room temp for an hour and try again.

Thanks everyone! I'll try cleaning the contacts and checking the temp. If that doesn't work, I'll test the voltage. Hopefully it's not dead, but I'm prepared for a new battery. Appreciate the help!