Cordless power tool brands make small changes to their products fairly regularly. Sometimes there might be a bump-up in specs, other times a small manufacturing optimization. Or, there might be a change to improve reliability or reduce assembly mishaps.
What I have learned over the years is that there a lot of of small and often overlooked changes, but they’re meaningful ones, with thought and planning behind them.
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I have an M18 battery that’s been here for a while, let’s call it a “test bench battery.” When I have to do some quick testing with a bare tool, or a reader has a quick question, this is the battery I use. It’s an older 5Ah battery.
This battery hasn’t been used for a while, as I’ve been bringing more tools to the bench with their own batteries of other sizes and styles, such as compact, HD, or High Output. I have still been using M18 XC-sized batteries, just not here and not this one.
I was looking at it, and there was a small spot of flaky material crusted on the outside by the terminal.
Corrosion of some kind? Maybe a drip of something? Did one of my kids sneeze on it with focused precision?
It didn’t look like a leakage or corrosion problem to me. But was it coming from inside the battery pack? I wanted to check, so I took it apart.
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Okay, so that’s interesting – there’s some kind of grease within the power terminals. My guess is that it’s some kind of dielectric or conductive grease for moisture and corrosion resistance.
But, I looked at some other M18 batteries – newer ones – and they didn’t have any such grease.
Why would older batteries have grease within the battery contacts, but not the newer ones?
I examined a couple of batteries and peeked inside 3 of them – an M18 4Ah battery from ~2012, a 5Ah battery from 2014, and a 5ah battery from 2018.
There are no battery codes – I’m going by the date codes of the injection molding.
I contacted Milwaukee about when the change happened and why, and will report back if I learn anything, although given the nature of the question I can’t expect to receive too many official details.
Milwaukee issued expanded warnings about their M18 HD 9Ah battery back in mid-2017. The batteries I have that pre-date that enhanced warning, which relates to avoiding exposure to conductive or corrosive liquids that can get inside HD 9Ah batteries, had an application of power terminal grease, and batteries from 2018 and later – at the least those I checked – do not have any grease.
Perhaps the tool connection interface was redesigned for better moisture and corrosion protection on the higher capacity HD battery, and then the changes were made to XC batteries as well.
The more recent batteries also look to have thick custom terminals soldered straight to the circuit board, while the oldest battery has still-beefy terminals but with short wires connecting them to the circuit board.
I found this to be the most interesting difference, but it’s also clear that Milwaukee implemented many significant changes when developing their 5Ah battery.
There are some common features, but the M18 XC battery design looks to have been largely redesigned for the launch of the 5Ah battery, or at least between 4Ah and 5Ah releases. Unfortunately, I don’t have enough of a range of batteries to be able to pinpoint when any of the major or minor M18 XC design changes were implemented.
I also can’t tell you what changes or improvements have been made to the current 4Ah batteries, if any, as I don’t have any recent 4Ah batteries to examine. I would assume so, at the least for streamlined parts sourcing and production optimizations, but it’s hard to say without proof or confirmation.
I can see that major changes were implemented between ~2012 and ~2014 (when the Milwaukee M18 5Ah launched), with changes being made to how the cells were housed, and it looks like the updated design has persisted in the years since.
Even the top cap, which house the spring clips that latch M18 batteries to their tools, has been significantly updated.
I find myself wondering what this change was for. It’s easier to reassemble newer M18 batteries than the older ones, but I would presume servicing frequency would be too low for this to be of repair benefit. The newer design looks to require more labor-intensive initial assembly, to lock the clips under its own plastic housing. Perhaps this helps with sealing the battery against moisture or other potential contaminants?
One of these days, I’m going to have to do a full comparative study, piecing together a picture about all the small changes I can observe and uncover.
Answering why any of the changes were made can be elusive. For instance, earlier circuit boards had blobs of clear resin covering some components, while the newer ones look to have thicker lacquer. The 2014 battery had a blob of white potting resin. Why then but not in the 2018 battery?
I hadn’t intended to take this close a look at Milwaukee’s M18 battery pack evolutions – I was only looking to eliminate any chance the odd film outside my battery’s terminal was coming from any of the Li-ion cells within – but this was fun, and I’m looking to learn even more.
This isn’t a full teardown, but I hope you still found it interesting.
Brian M
They also changed the M12 batteries but it’s more apparent from the outside than the M18 change.
Brian M
I just took a look at one of my 2015 batteries compared to the later 5.0. The main change from the old red board to the newer green board was the U1 IC. That is a different size and different pinout which is why you see the changes (Unpopulated D19, D12, Q18, R42, R67, etc).
I’d guess that it was simply a cost or availability of that IC. I presume same thing with the grease, probably saves cost(and in this case, not really needed).
Stephen Ditsche
I have 20 plus Milwaukee M18 batteries. I have burned out a few over the years. I have 7 guys using them all day long & have never seen one come apart. I have from XC up to 12.0 now & they all seem to be just fine.
R
Nice teardown article.I just bought the 8.0Ah High Output battery at the trimmer deal posted today – my first Milwaukee battery. Excited for when it arrives, I expect top tier quaity power!
Phil Gray
I am trying to find out what the actual terminals are called and where I can purchase them. I do alot of 3d printing and need some for a project. The older style with the wire crimped on it would be preferred. Thank you for any help.
Truman Conner
My milwaukee batteries are mostly 2 piece. I haven’t dropped them, they just come apart, not happy. Way spendy for that to be an issue.
Peter
We’ve dropped batteries, I have about 10 total, but I’ve never seen one break.
One of our older 2 CP2.0 batteries a starting to go bad, but I’ve never seen one come close to coming apart.
Frank D
Something must have happened, as there are screws holding the halves together …
Mr. Tate Nasty
Have you ever held the fuel gauge button in and it lights up a sequence? Does anybody know what this means?
Stuart
What kind of sequence? Other than from lowest to highest?
Mr. Tate Nasty
Push and hold the fuel gauge button in until it flashes. It blinks some kind of a code.
Stuart
Maybe some kind of self-diagnostic? This is the first I’ve heard of it, will try to look for more details.
Jim D
Max tools have this on their batteries and it is a counter of how many charges the battery has. I will check a few here and report back.
Jim D
There is not a lot of information for this on the web but I did my best to sort through what was available and did my own testing.
You push and hold the test button on your battery until the lights flash. There are 4 separate codes that will flash. The first light turns on for a moment, then the sequence starts. The sequence is giving you a 4 digit number. If there are no blinks, the number in that spot is 0. (example: first light blinks 1 time, second light 0 times, third light 4 times, 4th light 7 times, then the number is 1047). Then 2 lights flash indicating the second sequence is starting, then 3, then 4.
The first light sequence is an indicator of the battery health and potential issues. 0001 means good working order. 0101 means some issue with the battery or charger. I am not positive though.
The second light sequence is the days since the first time the battery was charged, after the initial factory charge has been depleted.
The third light sequence is the number of charge cycles the battery has gone through.
The fourth sequence is some sort of manufacturing date code, but I am not sure how to read this one yet.
The battery I tested had the below sequences;
0001 – Battery working
2937 – Days since first charge (stamped battery date code indicates the fifth week of 2012, so this makes sense.)
0181-Number of charge cycles
1552 – Date code. I am not able to quite figure this one out though.
The last number never changes so that is what leads me to believe this is a date code. The first number hasn’t changed either but I am going to check with a busted battery soon.
If anyone can clarify on this that would be great.
Bob
The last number labeled date code is probably coded the 52nd week of 2015.
This is a common date code used on many things.
You will see it on Printed circuit boards near the vendor ID info
Matthew
I dropped my Milwaukee impact from about 30 feet while hanging gutter. It slammed down onto the concrete. Climbed wearily down the ladder. I just knew it had broken. Nope! Works like a charm. Took a lickin’, kept on tickin’.
Michael Davis
I’ve never had an issue one with the batteries you sure you didn’t take the screws out first before you found out that they come apart I’ve had Milwaukee tools and their batteries for years and I can’t complain one it’s a good tool and a good battery
Evadman
Looks mostly like changes for manufacturing cost. For example, the wire terminals have to be hand soldered to the board, but the new terminals would work in a pick and place machine.
There’s some other changes in the board I see, such as dropping to 806 from 1203 sizes. Looks like some 402s too on the new board, but it sure looks like they are on 603 pads for some reason. It may just be your picture, but the conformal coating on the old battery looks absolutely terrible. The red board looks much better. I can’t tell if the new green board even has a conformal coating.
The dewalt, m12, and Bosch batteries I have taken apart didn’t have conformal coatings at all. Even a poor conformal coating would make a huge difference if water got into the pack. Good job milwalkee.
I’m quite curious as to what the board handles. The pictures aren’t high enough resolution to read the IC’s, and I am very curious about what all of the discrete transistors are for. I counted 19 on the red board, and a few of them don’t appear to be populated on the green board. It would be way cheaper to use a transistor array, unless they are discrete or power dissipation reasons.
There is also a power regulator, but it looks to be a lower voltage one that wouldn’t be able to handle pack voltage; probably 9 volts in and 3.3 out, which would use voltage from 2 cells and feed a microcontroller. I can’t find a crystal in the picture though, which means It could be on the bottom or I am totally wrong 🙂
On the ‘new’ boards, it looks like the unplaced components don’t even have solder on the pads. On the right side, there are 4 longer pads; the red board has solder and the green one doesnt. The missing solder means they used 2 different solder masks, on purpose. The board otherwise looks the same, same layout and everything. I wonder if they removed those components because they weren’t actually needed?
The white potting material looks like it is over a thermister. That would help it last longer since it appears to have longer legs, but costs a decent amount. It would probably also affect the accuracy by having a longer lag time due to thermal mass, so they probably stopped using it.
I’m making a ton of assumptions based on small pictures, so take with a grain of salt 🙂
Stuart
Thanks for your observations and insights!
I think I’m going to have to take some proper photos this week, maybe only comparing oldest and newest batteries for simplicity.
Aaron SD
It could be that they use the same boards for different batteries and populate it based on need. This could save some money using common boards.
Nathan S
“I am very curious about what all of the discrete transistors are for”
I wonder if they are using these for battery balancing. Q usually denotes a switch, while D usually denotes a diode. Transistors naturally consist of a diode and can be operated as controlled diodes to hold a relatively stable voltage. It looks like several are connected similarly. Just another thought / theory….
Lynyrd
The 5.0 is actually an old battery not produced since 2018 (Although still sold). The High Output 6.0 and 3.0 are the newest and would provide a starker difference. On Youtube AVE does an excellent job of explaining the internals of Power Tools and Batteries.
xrh07
5.0s are still being produced. The ones in the stores right now are going to have 2019 or 2020 manufacture codes.
They’re not going away anytime soon either. 6.0 HO batteries are too big for certain tools and the 3.0 HO batteries don’t put out quite enough power for certain tools.
5.0s are a happy medium between peak power output and runtime.
Big Richard
Agreed. I still run 5.0s on my drills/impacts for the reasons you listed. Also great when I want good run time but don’t care as much about power output, i.e. lights, radios, fan, etc.. Usually the best deal when it comes to Ah per $, too.
Farid
Two additional reasons for using the grease come to mind. One, is to minimize arcing (although I don’t why anyone would want to change a battery while the trigger is activated). The other is to help keep the contacts stay cooler. Localized heating at the contact point might have been high enough in some cases to damage the plastic in the immediate vicinity.
Bob
I wouldn’t expect to see many changes along the way with a battery pack. Any time you make a change to a design involves re-submitting the changes for agency approval(UL, CSA, ETL etc.) This is costly and takes time. Depending upon the design and the approvals you’re going for, there are many things that are checked and evaluated. Sometimes trace/component spacings are required to prevent arc over and things. One way to reduce the spacing on the circuit board is to conformal coat the board, which reduces the physical spacing requirements for traces and components. This is usually the case for hazardous location approvals, but could be required here due to the high currents involved in charging batteries. Hard to say without looking at UL specs for this product.
As a side note, I heard that Milwaukee tool never allowed their engineers to design using micro controllers. Everything had to be discrete logic or anaalog circuit designs. Maybe that has changed, but it used to be that way. So that may be one reason you see a lot of transistors on the board. More likely they are MOSFETs and are used for things like reverse polarity protection and turning on individual batteries during charging to facilitate cell balancing and control charging current and temperature of individual cells.
There is a whole lot of engineering design that goes into designing rechargable batteries. That’s why you don’t want to just go replacing a battery inside a pack with any old replacement cell. That’s a good way to start a fire! The old Nicad batteries were a lot more forgiving, but they aren’t nearly as good as the Litium packs.
Jim D
The only issue with the date code is that it is the 5th week of 2012 according to the stamped battery. Kind of confusing.
Kol
I got 24 m18 5.0, 2 hd 12.0 and a hd 6.0, and 12 m12 6.0. Only had to throw one away in 3 yrs. Milwaukee wins
Arnie Kopp
Thank you for all the great info. It just reaffirms my trust in Milwaukee tools.
Ian
Hey, nice article. I found it interesting but i didnt find the answer to my question. Hopfully someone checkes this page soon and can shed a bit of light on this.
On the side of the board youll see white rubbery adheasive with a bit of foam in it that you have to tear in order to open the battery pack.
Question: What is the purpose of the foam and what is the little antenna underneith it? Could that be the water damage indicatior?
Thanks for reading!
Stuart
I’m sorry, I cannot identify what you’re seeing.
Which battery are you looking at?
Swim
They are talking about the temperature sensor. I’ve seen two different sensors but both act as a temperature controller through resistance. As temp goes up, so would the resistance until it hits a maximum temp of X, at which point the safety switch opens. Power then should cease at one or both Line and Neutral pins (+)(-) thus cutting power until the temp drops below some threashold