A solid green light pops up on Milwaukee M18 chargers once the battery on them is at full power. After that light pops up, it’s time to take it off charge since it’s ready for use.
What do you do if your Milwaukee M18 battery says it’s fully charged but is still not working with your tools? Follow everything in the list below to go through everything you can try to fix this!
4 Fixes For A Milwaukee M18 Battery That’s Fully Charged But Not Working
- Issue With The Charger
I had the same thing happen to me not too long ago. I’d put my Milwaukee M18 battery on charge for a while, and the charger would show me a green light when I came back to it.
Everything seemed fine until I started to notice that the battery is lasting less and less time with each cycle.
As it turns out, the problem was actually with my Milwaukee M18 charger, and not the battery itself. There was an issue with the terminals, and it was giving me the same problem with all my spare batteries.
When I tried out a different charger, which you can see in the image down here, I didn’t get the solid green light until the battery was actually done charging.
The best way to confirm charger issues is with another charger. You can just use your same Milwaukee M18 battery on a different charger to see if it gives you the same trouble.
This is why it’s best to have spare batteries and chargers around if you work with tools often. Situations like these inevitably pop up, and spares make them much easier to deal with.
It’s very important to know the different meanings of the indicator lights on a Milwaukee M18 battery charger, so you’ll know if there’s a problem. I have made a short video about this and you can watch it below.
If you see a solid red, this means the battery is charging. This will become a solid green when the battery becomes fully charged.
A flashing red and green indicates a bad battery while a fast flashing red means the battery is either too hot or cold for charging. Lastly, a slow flashing red means battery charge is pending.
- Unbalanced Cells
Moving away from obvious fixes, I think the most common cause for this problem is likely the pack of cells inside the battery. These cells are what hold power and run the battery.
Milwaukee M18 batteries in particular have 10 cells inside of them. These cells are in 5 pairs of 2 cells. Each pair plays an equally important role in powering the battery, and stores equal power.
Things start getting weird when that changes. To elaborate, if one of the pairs doesn’t have as much power as the others, it causes an imbalance. This imbalance leads to issues like the current one.
Cell imbalances happen due to overcharging, leaving the battery without use for a long time, overheating, etc. All these things can bring the voltage of some pairs down.
You’ll have to take out the cells and take their reading like I have in the photo above. That’s the only way to know for sure if one of the cells is lower than the others.
This seems to happen a lot with 12.0 and 8.0 Milwaukee M18 batteries especially, and no one knows entirely why.
Anyway, when there’s an imbalance, some cells charge fully quicker than others. Once the charger spots even one full pair of cells, it’ll stop sending further power as it thinks the whole battery is at 100%.
Individually bringing their voltage by charging the problematic cells with a lithium-ion charger is the only way to deal with this.
- Dead Cells In The Pack
For anyone really unlucky, the problem won’t just stop at a simple imbalance. Instead, a pair of cells inside the Milwaukee M18 battery could be dead entirely.
The voltage on some cells can go so far down that it’s not safe to revive them anymore. That means the lithium-ion cell charger isn’t an option.
Again, the only real way to tell if a cell is dead is by taking its readings with a multimeter. So, get the cells out like me in the picture below, and start noting down their voltages.
If you catch any cells with a reading around 0.6V, those are entirely dead and you shouldn’t try reviving them. The only option to deal with them is to replace those pairs of cells entirely.
Depending on the type of Milwaukee M18 battery you own, you’ll need to find cells that are a perfect fit for its pack. Then, replace the dead cells in that pack with new functional ones.
After that, reassemble the pack and place it back into the battery. Now you’ll have a fully functional Milwaukee M18 again that doesn’t give you this problem anymore.
- Get A Whole New Battery
Got a really old battery or just don’t want to go through the hassle of dealing with replacement cells? Well, then your only option is to get a new Milwaukee M18 battery.
New batteries won’t give you any trouble and will last much longer than repaired ones. I recently got a new Milwaukee M18 battery myself, which you can see here.
Sure, it’ll set you back some bucks. But, it also saves a lot of time and is just a good investment all-around.
