Battery Not Charging on My Angle Grinder - Help?

Hey all, I've got a Makita 18V angle grinder that's been great for cutting tile and metal, but yesterday the battery wouldn't charge. It's the 5Ah battery, and I've tried a different charger, same issue. The light on the charger just blinks red. Any ideas?

First things first, check the terminals on the battery and the tool for any corrosion or debris. I've seen that cause intermittent charging issues. Also, make sure the battery isn't too hot - chargers have thermal protection and will refuse to charge a hot battery. Let it cool down for an hour, then try again. If that doesn't work, it might be a dead cell. You can test the voltage with a multimeter - should be around 18V. If it's a lot lower, the battery is likely toast.

Tim's right. I had a similar issue with my DeWalt. Turned out a couple of cells in the pack were fried from over-discharging. I use my grinder until it's completely dead sometimes, which is bad. Now I always keep a spare battery and swap them out when the power drops. If you're handy, you might be able to rebuild the pack, but for a 5Ah it might not be worth it. Just get a new battery - MAKITA ones are on sale on Amazon right now.

Thanks guys. I let it cool down and still not charging. I checked the voltage with a multimeter - it's reading 2.4V, so I guess it's dead. I was hoping to save it but I'll just buy a new one. Any tips to prevent this in the future? I mostly use the grinder for quick cuts, so I don't usually drain it completely.

Mike, 2.4V means a cell is definitely shorted. It happens. To prolong battery life, avoid storing them fully discharged or in hot cars. Also, don't run the grinder until it shuts off - stop when you notice a power drop. And use the correct charger - don't use a fast charger if not needed. Good luck, and be careful with that grinder - wear safety glasses and gloves!