Dremel 7700 won't charge - battery light blinking?

Hey guys, my old Dremel 7700 stopped charging. The charger light just blinks green when I plug the battery in. Tried different outlets, nothing. Battery is maybe 2 years old. Any ideas before I toss it?

These batteries have a protection circuit that can trip if they get too hot or too low. Try leaving it on the charger for 24 hours sometimes resets it. If not, it's likely a dead cell. You can try jumpstarting with a 9V battery (look up YT videos) but risky.

Hold up! Before messing with jumpstarts, check the contacts on both battery and charger for corrosion. Also, that blinking light could mean temp issue - make sure battery is cool. Safety first! Don't leave it charging unattended.

I had the same issue with my 7700. Turned out the charger itself was bad. Borrow a friend's charger to test. If it charges, you need a new charger. If not, battery is toast. Replacement packs are cheap on Amazon.

Since it's an older model, you can also open the battery pack and check individual cells with a multimeter. If one is below 1V, you can replace it if you're handy with soldering. I've revived a few packs that way. But be careful not to short anything!