The lights on the Milwaukee M18 charger aren’t the clearest thing, especially if you didn’t read the manual. There are obvious ones to signal things like complete charging.
Those aren’t what I’m here to talk about though. I’m here to focus on why there’s a red and green light flashing on your Milwaukee M18, what it means, and how you can fix it.
Before you read this article, you can watch first the short video I made which shows how you can troubleshoot this problem. You can watch the video down below.
In order to do this, you need to have another good Milwaukee M18 battery. Connect the positive and negative terminals of the two Milwaukee m18 batteries using a wire.
Let the batteries stay connected for around 15 seconds. Then, remove the wire and put the battery on the charger to charge again. You’ll learn more details about this fix below.
3 Ways To Fix A Milwaukee M18 Battery Flashing Red and Green
- Push The Battery In Harder
For a lot of people, the solution ended up being something as simple as just having to push the battery in harder. And, that doesn’t really surprise me.
Tough as it may be to believe, this is a super common problem new users have with the Milwaukee M18 batteries. It’s not exactly made clear how hard you have to press down.
Some new users might just push on it a little and set it into place. Then users think there’s an issue because the red and green lights come on in this situation. That’s what causes all the confusion.
The main reason for the red and green light coming on is a defective battery that’s not accepting charge. An improper connection is another reason for the battery not accepting power though.
So you might just be seeing this light because the battery isn’t in the charger all the way. That’s all you need to take care of to get rid of the light!
Take out the Milwaukee M18 battery and then wipe away its contact points while it’s out. Do the same for the points on the charger too. With those clean, slot the battery back in.
When doing this, don’t stop once the battery seems locked in place. Keep pushing until you feel the battery clicking into place, and then the light will change to solid red to indicate charging.
- Hot/Cold Delay
Another reason (and a much more serious one) for the red and green lights flashing is hot/cold delay. That’s the term for when the battery stops accepting charge because it’s too hot or cold.
Hot/cold delay happens due to overheating or overcooling. The latter usually only happens when you live in really cold environments, and the battery gets too cold.
Overheating on the other hand, is much more common for users across the world. That’s because it doesn’t solely depend on the environment. It can happen just because of regular use.
Due to that drastic rise or fall in temperature, the safety mechanism inside your Milwaukee M18 battery will stop it from charging. That’s because charging in this state is very unsafe.
Since the battery isn’t accepting charge, the red and green lights start flashing. The battery won’t charge while it’s too hot or cold, so the light will keep flashing.
As for fixing this, I strongly recommend that you don’t try anything. Overheating or overcooling are both serious issues and can lead to safety concerns if you’re not careful.
It’ll permanently damage the battery in some cases. In even worse cases, it could lead to injuries for users as well. So, instead of troubleshooting, set the battery aside for now.
Temperature issues go away on their own in a few hours if you keep the battery in a room-temperature environment. After that, it’ll be safe to charge again, and won’t flash red and green.
If you see a blinking red when you put your Milwaukee M18 battery on the charger it also means a hot/cold delay. I also have a video about this and you can watch it below.
The solution shown in the video is also the same as discussed earlier.
In case you want to know the meanings of the other indicator lights on a Milwaukee M18 battery charger you can watch the video I made about this topic.
If you see a solid red, it means it’s charging the battery. This will turn into a solid green once the battery becomes fully charged.
Related: Ways to Fix a Milwaukee M18 Battery Fully Charged but Not Working
As already mentioned many times before, a flashing red and green indicates a bad battery. And as discussed just a while ago, a fast flashing red, it means the battery is too hot or cold.
Lastly, a slow flashing red means battery charge is pending or charging will begin when the first pack is fully charged.
- Try Jumpstarting It
At this point, I guess the battery is flashing red and green because it’s actually supposed to. What I mean is; maybe the battery is truly defective and no longer charging like it needs to.
Whether you have a new battery or an old one, there is a common reason for this happening. It usually has to do with the battery being in storage and its cells dying down.
A lack of power slowly makes the cells lose their voltage. It eventually comes to a point where they’re dead and can’t be charged through normal means.
I have a method to get them working like they should, though! All you need for it is 2 razor blades, another battery, and some safety gloves to help you revive the cells.
See the terminals in the picture above? Take the covers off and stick one of the razor blades in the positive terminal, and the other in the negative terminal. Make sure the battery is off during this.
Line up the second battery to your Milwaukee M18 battery. The positive terminal of that extra battery should touch the razor blade on the positive terminal, and the same for the negative terminal.
Be VERY careful to not do this the other way around to avoid harm. Hold this for 30 seconds, and now plug the faulty Milwaukee M18 battery to its charger.
The red and green light should have stopped flashing. The method I shared will have revived the cells, and now the battery will charge like normal again!
