Milwaukee 28V Battery problem

[Jay64]

I have a set of Milwaukee 28V tools that I have had for a few years. Just the other day I went to charge up a couple of my battery packs. One charged up fine. The other one started off with a red light on the charger, indicating that it was charging, then after a while it changed to the alternating red/green light, indicating it had a problem. I took it off that charger and put it on the other charger that charged the other battery ok. It started showing that it was charging, and then that one too started flashing the red/green light. These packs have the button on the front that lets you check the power level via 4 lights. Both packs had 1 light left when they went on the charger. The problem pack now has 3 lights showing. Does this mean that the pack is out of balance? Is there anyway to test/fix this? I have long ago lost the manual for the charger.

 

[marty]

Jay64,
Try this place for the manual http://www.milwaukeetool.com

Milwaukee tools have had different warranties over the years. At one time they were guaranteed for lifetime.

 

[erdurbin]

Call a local service center and see if it is still under warranty. I am pretty sure they go by a number printed on the battery itself. I also think they can tell you if it has a bad cell or not.

Check with a volt meter and see if it shows any charge. If it does show charge, you may just have one or a few bad cells. I have taken many of these packs apart and there are usually 1-3 cells bad. However, some packs have all good cells, but they do not charge anymore like you are reporting. When you take them out individually, they charge fine, indicating good cells.
Even though LiMn do not need a BMS, these have one and if a cell gets below a certain voltage, it will not charge the pack at all. The only way I have found to fix this is below.
This may sound crazy, but I read somewhere else where you could possibly rejuvenate that battery by putting it on the charger and taking it off many times in a row until it finally starts charging properly. You may have to do this 100 times. I think this was for a LiFePO4 Dewalt 36v.

these are all just suggestions, let us know how it goes.

But after reading your post again, if you have 3 lights out of 4, doesn't that mean it is 75% charged?

 

[Jay64]

Yeah, it is indicating that it is charged 75%. I put it on my flashlight, and it powers it up. So it isn't like the thing is totally useless, dead. But there is some problem with it. I don't think it is the charger, since the pack behaved the same way on both chargers, and the other pack charged up fine on the one charger. One of the reason, that I'm asking about it is to try and understand the 'battery pack' concept better. I could just take it down to the service center and get it changed out without ever knowing what was wrong with it, but I wouldn't learn from that. Thanks for the suggestions on how to check it. I'm sure eventually I will end up taking it down to the sevice center and have it replaced. Might as well if it is under warranty. But in the mean time I want to test it as much as possible first.

Actually, I just remembered that I have my tool box right here in the kitchen. I pulled out that battery and another battery that also is showing 3 lights. They both registered the same on my meter, looks like its about 22 v??? I will try to put them both back on the charger and check them when they are full, well, at least if the one gets full.

 

[Ypedal]

Can you check the contacts ? they may just be dirty and need cleaning , giving the charger a bad reading.

If out of warrantee.. i'd open them up, but otherwise bring it back for a fresh one !