Milwaukee M12 batteries are made to last a long time, both in terms of battery life and lifespan. However, as with any other battery, they eventually have some complications pop up.
Amongst these complications, a really common one is the Milwaukee M12 battery not holding charge, or getting to full bars. This is different from your Milwaukee M12 battery showing green but not charging to full.
Is that happening to you right now? If yes, try my list of fixes below!
Read: Common Milwaukee M12 Impact Wrench Problems Troubleshooting
Milwaukee M12 Battery Not Holding Charge and Getting To Full Bars
- Manufacturing Defects
This is a super commonly reported problem, and there’s a good reason for it too. Some Milwaukee batteries have a known manufacturing defect that stops them from holding charge properly.
It was especially common at a certain time and with specific models of batteries. Users who just recently got their Milwaukee M12 battery likely got one with this defect.
You don’t have to worry about troubleshooting it if that’s the case, though. Because it’s a new battery, an issue like this is something the company will take care of for you.
Talk to Milwaukee customer support. Tell them about the problem you’re having with your new battery. They’ll likely recall it, and send a new and fully functional one.
On the other hand, if you’ve been using this battery for a while, I doubt manufacturing has anything to do with it. It’s likely something else that happened, so let’s see what that might be.
- Try A Different Charger
Before you’re set on blaming the battery and looking at what’s wrong, the first troubleshooting step I recommend actually has to do with the charger. It’s just as likely to be the cause.
The charger may be faulty, not providing enough power to the battery. That’s stopping it from charging fully and getting to full bars. So, ensure that that’s what’s up by trying a different one.
Instead of buying a whole other charger, you could check if a local mechanic or even someone you know has one. Borrow it to see if the Milwaukee M12 battery charges fully with it.
Once you have a different charger to try it on, plug the battery into it and see if that works. In case it doesn’t, you know that the battery is to blame, and not the charger.
But, if that different charger works and your current one doesn’t, you know the issue was because of the charger. You’ll have to buy a new one so that your battery can charge normally.
If the charger was new too, you should be able to claim a warranty on that as well. Milwaukee will send you a new one after that, that works without any worries.
- Cells Inside Have Reduced Voltage
Your Milwaukee M12 battery may not be charging to full bars because it no longer can. This can happen when the individual cells inside start to lose balance in their voltage.
Something like that is a direct result of one of those cells losing their capacity. When one cell loses its capacity, it also loses its voltage. That means it’s out of balance with the other cells.
Only one of the cells inside your battery is problematic. That’s why it’s still working, but not holding a charge properly or getting to full bars. There’s a way to confirm this.
Usually, the charger will display a flashing red and green light if the battery isn’t charging. This means it has detected a bad battery.
I have a short video about how you can fix this issue and you can watch it below.
You would need another similar healthy battery here to jump start and reset the bad battery. Using two wires, connect the positive and negative terminals of the two batteries.
Leave it for around 15 seconds and then disconnect it. Then, try to recharge it on the Milwaukee charger and it should now be charging normally.
It’s very important to know the meaning of the different lights on a Milwaukee M12 battery so I have a short video about this topic. You can watch it below.
If it shows a solid red it means the battery is charging normally and this will turn into a solid green when it becomes fully charged.
As mentioned earlier, a flashing red and green indicates a bad battery. If it displays a flashing red, this means a hot/cold relay.
For that, open the covering of your Milwaukee M12 battery. With the covering open, you’ll see a pack of cells held together inside. Take these out, as I have in the image below.
After you have the cells exposed, you’ll need a multimeter. With something that can help you measure the voltage accurately, see if any of them are weaker than the others.
Get a suitable replacement cell for the pack if you find any that have bad voltage. That’s what’s stopping your Milwaukee M12 battery from holding charge and getting to full bars.
Related: I Left My Milwaukee M12 Battery on The Charger Overnight
I have a video which shows how to identify a defective cell inside a Milwaukee M12 battery and you can watch it below.
You need to open the battery and check the individual cells using a multimeter. Each battery cell should have an output, and if not, it’s identified as a bad battery cell.
- Old Battery That’s Dying Now
Even if the cells are fine, if you have a really old Milwaukee battery, its components may just be dying. Dying chips or circuits are quite common after a few years of regular use.
You can try to “reset” an old battery in order to make it charge normally again. I have a video which shows how you can do this and you can watch it below.
To fix this issue, you would need to use another healthy battery with the same specs as the faulty battery. Using a wire, connect the positive and negative terminals of the 2 batteries.
After 15 seconds, try to recharge the battery again. It should be charging normally this time around.
These are the types of things that regulate certain functions of the battery. When they die, those functions begin to fail. This includes proper power flow and the capacity of the battery to hold charge.
So, it’s best to replace a Milwaukee M12 if it’s quite old and being problematic. The parts inside are starting to give in, and you’ll have to deal with issues until you get a new one.
A new battery may be costly, but it’s a necessary expense when your current one is too old. On the bright side, as I mentioned at the start, Milwaukee batteries are made to last a long time.
So, once you get a new one, you can rest assured that it will serve you reliably for years, and give you your money’s worth without further hassles!
