Dewalt 20V Max battery not charging? Any tips?

Hey guys, my Dewalt 20V Max battery (the 5Ah one) won't charge. It's been working fine for like a year, but now when I put it on the charger, the light just blinks red real fast and nothing. I tried another battery and it charges fine, so it's not the charger. Anyone seen this before?

Had that happen once. Could be a dead cell or the contacts are dirty. Check the battery terminals and the charger contacts for any grime. Also, try leaving it on the charger for a few hours even if it blinks - sometimes it resets. But if it's still under warranty, get it replaced. Safety first, don't try to open it up if you're not sure what you're doing.

yeah, I've revived a few of these. If cleaning don't work, sometimes it's just a balance issue. Try putting it on a different charger if you can, or even a slow charge from a power bank (but careful!). But honestly, if it's the 5Ah, they're known to have cell problems after a while. Might be time for a new one. I've had luck swapping cells if you're handy with soldering, but that voids warranty.

Thanks guys. I cleaned the contacts and tried leaving it on for an hour, still no luck. I guess it's toast. I'll grab a new one on sale. @DeWaltDan53, I might try the cell swap on the old one for fun - got a guide? Thanks again!