Dewalt 20V Max battery not charging? Help!

Hey guys, my Dewalt 20V max battery (the 5Ah one) won't charge. It's been sitting for a while, and when I put it on the charger, it just blinks red. The charger works fine with other batteries. Any ideas what's wrong?

Sounds like the battery cells might be unbalanced or a cell went bad. Try leaving it on the charger for a while - sometimes it takes time for the BMS to recalc. If that doesn't work, you can try jumpstarting it with a fully charged battery if you have another one. But be careful, use thick wires and just touch the terminals for a few seconds.

I had a similar issue. For me, the battery was just too cold. I warmed it up a bit (not in the microwave lol) and then it started charging. Also check the contacts for dirt or corrosion.

Thanks for the tips. I tried leaving it on the charger overnight but still blinking. I don't have another battery to jumpstart it. Might just have to buy a new one. Any way to revive it without another battery?

You could try a manual balance charge using a hobby charger if you have one. Open up the battery (carefully, these can be dangerous), check individual cell voltages. Most likely one cell group is below 1V and the BMS won't charge it. You can charge that group directly with a Li-ion charger set to 4.2V. But if you're not comfortable, probably just get a replacement. Safety first!