My grinder keeps stopping after a few seconds - help!

Hey all, been using my angle grinder for a while now, and today it started dying on me. I'll turn it on, it spins up, but after like 5 seconds it just cuts out. Let it sit for a minute and it'll do the same thing. Battery is freshly charged (I checked with another tool). Any ideas? It's a cordless 18V.

That sounds like a classic overheating issue or maybe a bad trigger contact. I've had that happen when my grinder's brushes were worn out. You check those? If it's brushless, maybe the switch is getting flaky. Could also be the battery's overload protection kicking in. Are you using a high-capacity battery? Some smaller ones can't handle the draw.

I've seen this on job sites. First thing, check the carbon brushes if it's a brushed motor. They wear down and lose contact when they get hot. Also, make sure the battery contacts are clean. But if it's brushless, could be the motor control board. Also, are you pressing the safety lock? I've had guys accidentally hit that and it shuts off. But since it restarts, probably not that. Could also be a thermal cutoff - giving it a minute lets it cool down. Check for any debris blocking the vents.

Had this exact problem with my 12V grinder. Turned out the battery was fine, but the tool's internal temp sensor was triggering because the gearbox was dry. A little grease on the gears fixed it. If you've never greased it, might be worth opening it up. Just be careful not to overdo it. Also, what brand? Some are known for this.

I'd also check the lock-on button. If it's partially stuck, it can cause intermittent power loss. But keeping with the safety theme - make sure the disc isn't binding. If the arbor is loose or the disc is warped, it can cause extra drag and trigger the overload. Also, if it's a variable speed, perhaps the electronic speed control is acting up. But before you go tearing it apart, try a different battery just to rule that out - even if it's charged, it might have a bad cell.