Impact wrench battery won't charge - any ideas?

Hey guys, my Dewalt 20V impact wrench stopped charging. It's about 2 years old, used it heavily. The charger shows a solid red light. I tried a different battery and that charges fine. So it's the battery. Is it toast or can i fix it? I don't want to drop $100 on a new one if i can help it.

How many charge cycles? Dewalt batts are tanks but they do die eventually. If it's still under warranty (3 years usually), file a claim. If not, you could try jump starting it with a multimeter, but honestly I'd just replace it with a genuine Dewalt. Knockoffs catch fire. Stick with the brand.

Before you buy new, try this: some chargers have a reset. Unplug the charger for 10 mins, then plug it in with the battery off. Also check the contacts on the battery - if they're corroded, clean with alcohol. If that doesn't work, you can rebuild the pack. It's cheaper if you're handy. 3D printer mods? Nah. Just get a compatible off-brand from Amazon for $40. I've had good luck with one.

Solid advice. I've resurrected a few packs by replacing the cells. If you have a soldering iron and a spot welder, you can do it. But be careful - lithium cells are no joke. If just one cell group is dead, the BMS locks it. Check voltage on each bank. If one is below 1V, it's shot. Otherwise, you might just need a new BMS board. They're $10 on eBay. I'd say try the cheap fixes first.

Hold up. 'Off-brand from Amazon'? That's how you ruin your tool. The charger communicates with the battery via SMBus. If the BMS is fried, the charger won't charge it. A genuine Dewalt battery uses temperature sensing and cell balancing. Cheap ones skip that. If you want to fix it, open it up and measure individual cells. If any are below 2.5V, replace them with high-drain cells like Samsung 25R. I can send you a teardown guide if you want.