Can I Restore Full Charge on Tool Battery

[BHopkins]

A few weeks ago, I removed an M18 Red Lithium 8AH battery from the charger while it was still charging, so I could complete a task. Since then, the battery no longer lasts very long, perhaps only about 1/4 - 1/3 of it's normal life. The charge indicator LEDs show that it is fully charged, but it just doesn't last as long as it used to.

It seems that it is getting a little better with each usage and recharge. But I was wondering if there is any particular way to help it reach it's full capacity once again.

I really like this XC8 battery, as I use it on the string trimmer and leaf blower. Before the incident, I was able to trim my entire yard, and get most of the grass clipping cleaned up, before having to change to another battery. Last time I got about 1/2 the edging done before the XC8 was dead.

 

[Rand]

I suspect it has nothing to do with removing it while partially charged.
How old is this battery? Is it possible to warranty it?

 

[cptbarkey]

Is it still under warranty? this page summarizes the various batteries and their warranty.
https://www.redtoolstore.com/blogs/...4wuLU0DRF8CKHtipbZGOw84ucxJpYrZ5RUvrPWedyiV6U

Its possible to refurbish it if you are skilled with small electronics and study several hours of YT videos.
The cells in your battery may have become unbalanced, there is a procedure and tooling to rebalance them, but its involved.

 

[Hirev]

How old is this battery?

 

[BHopkins]

I suspect it has nothing to do with removing it while partially charged.
How old is this battery? Is it possible to warranty it?

It seemed odd that simply removing the battery from the charger early would cause this, but the short life started immediately after that event. Before, it was fine.

I'll have to find the receipt, but I believe it is about 2 years old. I hadn't even thought about getting Milwaukee to warranty it. Thanks for pointing that out, everyone. I tried to find my battery on the website that @cptbarkey provided a link for, but couldn't find any numbers on my battery that match up with what is shown on the website page. But by description, it should have a 3 year warranty.

 

[JHZR2]

Li-ion doesn’t get “memory”. There are some rudimentary controls/bms, and likely some balancing circuitry. It ,ay have been unbalanced and didn’t complete.

You can put a meter in the slots and get the individual voltages. They should all be very close. What do you measure?

 

[boom10ful]

Li-ion doesn’t get “memory”. There are some rudimentary controls/bms, and likely some balancing circuitry. It ,ay have been unbalanced and didn’t complete.

You can put a meter in the slots and get the individual voltages. They should all be very close. What do you measure?

The battery balancing chip is inside of Milwaukee packs but is not activated. There is no balancing on their packs. I recommend manually balancing the cells every 2 years, especially the higher amp hour packs

 

[ripcord]

Lithium ion batteries gradually degrade over time no matter what you do with them and there is very little than you can do to recover any lost capacity. The best way to slow the degredation is to store them at 50% state of charge.

 

[Carmudgeon]

BMSes can be smart, or dumb. The one in a tool battery is probably isn't Einstein-level, but even the smarter ones can get out of sorts, lose track, and need to be recalibrated.

I'm not on Team Red, but some intrepid member might have done a teardown and have a firmer handle on how those packs function.

Before doing anything else, try draining the battery to empty, then recharging it to full again, and leave it on the charger for a while after it indicates full. The cells are probably fine, but the BMS needs to be kick-started and "reset."

A smart BMS, like the one in your laptop, would have a history of data, and combine that with current readings to better determine the state of the battery.

A dumb BMS, like inside a tool pack, is unlikely to be that deep, and probably relying on readings, and maybe some dead reckoning, which was probably thrown out of wack when removed from the charger with a partial charge.

Also keep in mind batteries are either a jelly roll, or a sandwich of components. Not an pinpoint exact science but an educated guess as to how many electrons a smashup of chemical elements can pass. Only way to tell for certain what a battery can do is in use, under load.

If Team Red's warranty process is easy, that may be the best option.

 

[NYEngineer]

My brother gave me a "Super Charger" or whatever Milwaukee calls the fast charger. I used it a few times to do 12 volt batteries for my heated hoodie. I noticed the battery didn't last very long when it was charged in that charger. I used the small regular charger and the batteries were back to normal. Now I only use the fancy charger for M18 batteries and only every fourth charge.
It also seems all batteries take a charge better when they're allowed to cool completely after use.
I have some really old Milwaukee batteries.

 

[BHopkins]

Li-ion doesn’t get “memory”. There are some rudimentary controls/bms, and likely some balancing circuitry. It ,ay have been unbalanced and didn’t complete.

You can put a meter in the slots and get the individual voltages. They should all be very close. What do you measure?

I found a pinout for M18 batteries, and this is what it says.
Pos
Thermistor
Data
Identification
Neg

When I probed it, I got 19..9 vdc across neg and the data terminal and 20.2 vdc across neg and pos. No reading (vdc) across neg and the other two terminals. These two voltages seem pretty balanced.

My brother gave me a "Super Charger" or whatever Milwaukee calls the fast charger. I used it a few times to do 12 volt batteries for my heated hoodie. I noticed the battery didn't last very long when it was charged in that charger. I used the small regular charger and the batteries were back to normal. Now I only use the fancy charger for M18 batteries and only every fourth charge.
It also seems all batteries take a charge better when they're allowed to cool completely after use.
I have some really old Milwaukee batteries.

I also have a Rapid Charger and a few regular Milwaukee chargers. If memory serves me correct, I have been using the Rapid Charger on this XC8.0 battery. And the last couple times I charged it on the regular charger. Perhaps that is why the last couple uses, it is starting to yield more capacity?

Agreed on charging batteries when they are cooled off. Although MIlwaukee chargers are supposed to check the battery temperature, and will not charge them until the temperature is under some preset threshold, I usually let my batteries set for an hour or so after use, before charging them. It costs me nothing but time, in hope that it extends the life of the batteries.

 

[gathermewool]

How low do you typically discharge them to? I have a LFP battery that has lost some capacity (it mainly sits at 80-100% charge) and the etherwebs said to discharge it to zero and then charge it fully to recalibrate the BMS.

Now, if @boom10ful is correct that may not help. I have only done one discharge cycle using my CPAP and the above-mentioned LFP battery and it still didn’t last the night like it had in the past, but did last a little longer. Maybe a bad example dude to so many factors from using something like a CPAP, but it was a useful datapoint for me, at least.

I plan to run the battery down to zero at least once more to see if it helps. It’s a LFP battery so I’m not worried about the cycles.

 

[BHopkins]

How low do you typically discharge them to? I have a LFP battery that has lost some capacity (it mainly sits at 80-100% charge) and the etherwebs said to discharge it to zero and then charge it fully to recalibrate the BMS.

I almost always run this battery all the way to empty, when my tool shuts down. It is definitely getting a full charge cycle each time.

 

[NYEngineer]

The tool not running on the battery is not zero. You need a radio or a light or something to take it down further. I used to use the radio to run my old DeWalt NiCad batteries down to nothing. They lasted an insanely long time as well because I always discharged them to zero and then recharged them.

 

[Carmudgeon]

The tool not running on the battery is not zero. You need a radio or a light or something to take it down further. I used to use the radio to run my old DeWalt NiCad batteries down to nothing. They lasted an insanely long time as well because I always discharged them to zero and then recharged them.

For anyone reading this to imply that the OP do the same with this battery pack, it would not be a wise idea.

Part of the BMS' job is to prevent damage to Lithium cells by allowing them to suffer deep-discharges. Not unlike a car battery, Empty ≠ zero voltage, or anything below ~3V. Conversely, allowing them to be stored at full charge is also not optimum for best lifetime.

Lithium cells like to operate within a narrow voltage range, and though often ignored in real world practical usage, the best practice is to keep them between 20-80% SoC if better durability is a desired goal.

That said, they should be "exercised" and run through a complete cycle occasionally, for their health, and to keep the BMS happy. Keeping that laptop that only does desk duty connected to AC power all the time does no favors to its battery.

 

[jhellwig]

Milwaukee cannot make a good battery over 4 or 5 AH from what I have found. Lots of people have issues with the bigger ones having much shorter lives than they should. I have 8 year old 9.0 and 4 year old 8.0 batteries that have lost tones of capacity but my 13 year old 3.0 ones are still going full bore.

 

[Pablo]

I jumped on the nut barge

Well awhile ago with M12. I’ve been using Waitley aftermarket batteries in all my Milwaukee 12V stuff. Big ones too. Not one problem

So I bought two 18V Waitley for the Makita. Fantastic batteries with digital charge read out even

The only aftermarket batteries I would recommend

 

[ripcord]

I jumped on the nut barge

Well awhile ago with M12. I’ve been using Waitley aftermarket batteries in all my Milwaukee 12V stuff. Big ones too. Not one problem

So I bought two 18V Waitley for the Makita. Fantastic batteries with digital charge read out even

The only aftermarket batteries I would recommend

Wow! Those are inexpensive and a good deal even if the amp hour ratings are a little optimistic.

 

[Cujet]

"If" a cell or two has dendrites, that will reduce the capacity. One way to manage this is occasional high discharge rates. Most tools are designed not to place a very high discharge rate on the cells to ensure an overall long battery life. But the big grinders working hard are often the Amp draw kings.

 

[cptbarkey]

Milwaukee cannot make a good battery over 4 or 5 AH from what I have found. Lots of people have issues with the bigger ones having much shorter lives than they should. I have 8 year old 9.0 and 4 year old 8.0 batteries that have lost tones of capacity but my 13 year old 3.0 ones are still going full bore.

I have read the same complaints, yet I have owned a few 6ah and 8ths with zero issues, now a few forges (8 and 12) and again zero issues.