Battery not charging on my Makita sander - anyone else?

Hey guys, I've got a Makita 18V sander that's been sitting for a few months. Went to use it today, and the battery won't charge. Plug it into the charger, and it just blinks red. Tried another battery and that one charges fine. Anyone know what's up?

Sounds like the battery might have gone into deep sleep from sitting too long. Try giving it a jumpstart: put it on the charger for 30 seconds, then take it off and tap it gently on a hard surface (not too hard). Put it back on charger and see if it starts. If not, the BMS might be shot.

Hold up, before you go tapping anything, check the terminals for corrosion or gunk. Also, make sure the battery is at room temp - charging cold batteries can cause issues. If that doesn't work, it's probably a dead cell. Time for a new battery.

I've revived a few Makita batteries by taking the pack apart and checking the individual cells. If you're handy with a multimeter, you can test each bank. But be careful - those 18650s can be dangerous if shorted. Might just be cheaper to buy a new one.

Thanks all. Tried the tap method and cleaning terminals - no luck. Guess I'll just grab a new battery. Appreciate the help!