My drill's battery won't charge!

Hey folks, I've got a DeWalt 20V drill that's been working great for years. But now the battery won't charge at all. When I plug it in, the charger light stays red for a second then goes out. Tried a different battery, same thing. Anyone know what's up?

First thing, check the charger itself. If it's doing that with multiple batteries, the charger's probably toast. Don't go probing it if you're not comfy with electronics, but you can usually test the charger with a multimeter if you have one. Also, sometimes the contacts get dirty. Try cleaning them with a bit of alcohol.

DeWalt? Shoulda bought Milwaukee. But seriously, check the battery terminals. If they're not making good contact, it won't charge. Also, some chargers have a reset button or you can try unplugging it for 10 mins. If that fails, it's likely a dead charger.

I had a similar issue with a Makita. Turned out the battery management system (BMS) on the battery was fried. If you have a multimeter, check the voltage of the battery. If it's below 10V, the BMS may have shut it off. Some chargers can't revive that. You might need a new battery or a cheap "revive" charger. Also, check for swollen cells - if they're puffy, toss it.