Battery Not Charging? Milwaukee M18 18V Lithium-Ion Won't Take a Charge

Hey all, my Milwaukee M18 drill battery just stopped charging. I plug it in, the charger light blinks red/green, and nothing. The battery is a few years old but was working fine yesterday. Any ideas? I've already tried a different outlet and cleaning the contacts.

Hey Hank, that red/green blink usually means the charger thinks the battery is too hot or too cold, or there's a cell imbalance. Let it sit for an hour at room temp and try again. If that doesn't work, it might be a dead cell pack. If you're handy, you can test the voltage with a multimeter—if it's below 10V, it's toast. Otherwise, check if your charger is okay by trying a known good battery on it.

I had a similar thing happen with an old drill. Sometimes it's the battery contacts inside the tool get bent. They can also get 'confused' after a deep discharge. Try tapping it gently on the bench (not too hard, lol) and then plug it in. Also, check the charger's manual—some chargers have a reset function like unplugging for 5 mins. But if it's over 3 years old, might be time for a new battery anyway.

Honestly, with Milwaukee, batteries do wear out. If you've had it a few years and it's not holding a charge, it's probably end of life. I've revived them sometimes by putting it in a freezer for a few hours (yes, sounds crazy but works for some) then charging. But it's temporary. If you're using it daily, consider investing in a high-output battery. But first, try SocketSarah's tip about letting it acclimate—temperature issues happen a lot in garages.

I'm a Milwaukee guy, but I've seen this. The blinking pattern is key: if it's red-green-red-green fast, it's thermal. If it's slow, it's communication error. Check if the battery is swollen—if it is, don't use it, recycle. If it's not, try to update the charger firmware? Wait, that's for the newer ones. Actually, just buy a new battery—it's not worth the headache. I had one fail after 5 years, and a new one fixed it. But also check your charger: is the contact pin on the charger moved? That can happen.