My DeWalt impact driver won't charge - any ideas?

Hey all, my DeWalt 20V max impact driver just stopped charging. The battery doesn't charge when I put it on the charger, and the charger light stays red. I've tried a different battery and it charges fine, so it's the battery. Any thoughts? It's about 2 years old, used regularly.

Could be a dead cell in the pack. If you're comfortable, open it up and check the voltage of each group. Sometimes a bad cell will cause the charger to not even start. Also, make sure the contacts are clean - I've seen corrosion cause weird issues. Safety first: disconnect and discharge before prying.

Yeah, what Steve said. Also, check if the battery has a reset button - some DeWalts have a little button you press with a paperclip. If that doesn't work, it might be time for a new battery. But before that, try leaving it on the charger for a few hours even if the light is red - sometimes it slowly balances. But if it's not charging at all, it's likely toast.

I had the same thing happen to one of my 5Ah packs. Turned out it was a bad terminal inside the battery - the plastic holder cracked. I took it apart, resoldered, and it worked. But if you're not into that, just buy a new one - they go on sale often. Also, make sure you're using the right charger - the fast charger might not work with older batteries.

Thanks guys! I'll try the reset button and check the contacts. If no luck, I'll probably just get a new one. Appreciate the help!