Many cordless power tool brands – Dewalt, Milwaukee, Makita, Bosch, and others, have faster and slower battery chargers.
Shown here is Milwaukee’s M18 Dual Bay Rapid Charger, which charges batteries faster than their standard charger. Their Super Charger can recharge High Output M18 batteries at an even faster rate.
Do fast chargers negatively affect power tool batteries? This is an increasingly common question, and a very good one.
Advertisement
A reader wrote in today, prompting me to think about this again. Mosh wrote:
Does charging my tool battery with a fast charger kill them? My Dewalt fast charger has a built in fan for cooling.
In theory? Yes. In practice? Probably not.
Lithium-ion cordless power tool batteries are prone to wear. Each battery has x-number of charge cycles before it loses y-percent of its initial charge capacity. Once the battery pack holds noticeably less charge than before, or fails completely, it’s due to be replaced.
So, the question isn’t whether a fast charger will damage or “kill” batteries, but whether it will accelerate the wear on that battery.
There are several factors that can shorten a battery’s usable life, with heat perhaps being the most significant.
Advertisement
Charging a battery pack creates heat. Charging a battery pack at a faster rate leads to more heat.
Logically, if faster charging means more heat, then doesn’t faster charging also shorten the life of Li-ion battery packs?
Faster chargers typically feature active cooling that helps batteries shed their heat at a faster rate. Charging rates also typically slow down a bit once a battery reaches higher charge capacity, such as 75-80%.
Most sophisticated chargers also contain thermal sensors and will not charge a hot battery.
As long as the heat is controlled, there’s less chance of accelerated wear.
When Milwaukee’s M18 Super Charger came out, I asked them if their Rapid Chargers and Super Chargers affect the usable lifespan of battery packs.
If you have two battery packs, such as M18 5.0Ah XC, with one recharged on a standard charger and the other on a Rapid Charger, will there be any difference in charge capacities or usable lifespan after 50X/100X/500X use and charge cycles?
Here’s what they said:
No, there won’t be a difference in lifespan of batteries between standard, rapid, and super charger.
Packs outside of High Output have a ‘cap’ where they simply will not charge faster on this charger. That ‘cap’ is comprised of many things, like cell chemistry. The high output packs can handle this faster rate without degrading life due to the chemistry and mechanical design of the cell tech.
It’s possible for faster chargers to accelerate battery wear, but it’s also likely that power tool brands take temperature thresholds into account when designing their faster chargers.
In 2019, when I was at Milwaukee Tool’s headquarters for a new product media event, we were taken to one of their battery labs, and I was given permission to walk around while a product manager went over battery pack design basics.
I won’t go into specifics, but the nature of the equipment in the room indicated a level of Li-ion battery cell and battery pack research I never would have expected from a power tool brand.
A few years earlier, Milwaukee’s battery lab at the time included rows and rows of power tool battery and charger banks that were used to automatically cycle their battery packs, as well as competitors’. They have since moved this lab to a different location, and I have not seen it since.
I would assume at least this level of battery development and characterization sophistication from most major power tool brands today.
Can it be guaranteed that faster charging won’t damage a battery pack? No, I don’t think so.
But, to be frank, I have a bit of faith that power tool brands are careful in their charger designs.
The fact of the matter is that battery packs are still wearable products that will eventually need to be replaced.
For my own use, I weigh present value vs. future costs – I use a fast charger if I need the speed, and a standard charger if or when I don’t.
Hypothetically, if a battery that is always fast-charged gives me 200 charge cycles before it loses capacity, vs. 300 charge cycles for a battery that is always slow-charged, is it worth it?
Do you leave your battery packs fully charged for long periods of time? Do you completely drain your battery packs every time before recharging? There are lots of factors that can accelerate wear.
Unfortunately, answering the question about whether faster charging accelerates battery wear requires significant time and equipment investments.
Brands – or at least Milwaukee Tool – say that no, their faster chargers do not accelerate Li-ion cell degradation.
There are a lot of different cordless power tool brands, a lot of different battery pack sizes, and a lot of different chargers. It’s possible that faster charging can negatively affect some battery packs.
Faster chargers tend to be premium add-ons, or are sometimes included as standard with higher capacity batteries. Some other brands’ fast chargers are their “standard” chargers, with slower chargers being value kit inclusions.
If you’re worried about the potential for heat-related wear, simply don’t use a fast charger unless you need the speed benefits.
I think that this is a valid concern, especially with how much high capacity battery packs cost to replace. But, those pricier higher capacity and higher output battery packs can also handle faster charging rates.
How about an example.
Milwaukee Tool has table that shows how fast their M12 and M18 batteries recharge with different chargers. Their Rapid Charger is faster than their standard charger, and their Super Charger is faster than both when recharging High Output batteries. (This is because High Output batteries have a lower charger density and heating profile during charging.)
On Milwaukee Tool’s 3 tiers of chargers, the fastest that an M18 2.0Ah battery can be charged is 25 minutes. The fastest that an M18 compact 3.0Ah HO battery can be charged is 35 minutes. Their M18 6.0Ah XC battery charges in 64 minutes on a Rapid Charger and 35 minutes on a Super Charger.
A compact 3.0Ah battery is likely built with 21700-sized 3.0Ah Li-ion cells. An 18V or 20V Max compact 3.0Ah battery pack would have (5) of these cells.
18V or 20V Max 6.0Ah batteries are likely built with (10) 21700-sized 3.0Ah cells. (Some brands, such as Makita and Bosch, have 18V 6Ah batteries with 18650 cells.)
Okay, so Milwaukee’s M18 CP3.0Ah and XC6.0Ah batteries are built with similar or even identical 3.0Ah cells.
If a Super Charger can recharge each cell in a CP3.0Ah battery in 35 minutes, why couldn’t it also recharge each cell in a XC6.0Ah battery in the same amount of time? If you double the current across double the number of cells, each cell should create comparable levels of hear, right?
Thermal dissipation is important here. As long as the batteries can shed the heat, why would there be any negative effects from a faster charging rate?
A Milwaukee M18 XC8.0Ah battery is built with (10) 4.0Ah cells, and their HD12.0Ah battery is built with (15) 4.0Ah cells. The Super Charger recharges the 8.0Ah battery in 45 minutes, and the 12.0Ah battery in 60 minutes.
Hypothetically, since each battery has 4.0Ah cells, shouldn’t it be possible to deliver 50% more energy to recharge 50% more Li-ion cells in the same amount of time?
But, the 12Ah battery takes 33% longer to recharge than the 8Ah battery.
This could be due to power limitations, but it likely has more to do with cooling. When you have a 15-cell battery pack, there’s a row of Li-ion cells sandwiched between two others, leading to more complex heat distribution and dissipation profiles.
Maybe I’m overly optimistic, but I like to think that, as part of the design process, brands take into account how fast their batteries can be recharged without added degradation over time.
If we disregard tool brands’ assurances, and we cannot easily test this experimentally, what about anecdotal evidence?
Faster power tool battery chargers have been around for quite a few years now.
Have any of YOU experienced noticeably accelerated power tool battery wear after using fast chargers long-term?
Adam
I’ve always figured the companies knew why they were doing. While I’m sure there is possibly
a tiny measurable difference down the road, it’s probably not noticable.
If there was a difference, you would hear a lot more complaints from users experiencing poor battery performance. I don’t think any of the tool companies would want to deal with this
Louie Orama
My thoughts VERBATIM while I read the post. “Is this gonna give us a headache? If so, don’t release it.”
David A.
Exactly what I thought as well. If large commercial users suddenly noticed a decrease in battery performance they would definitely object (and rightly so). The incentive for the tool brands to keep customers satisfied is pretty strong because competition in the industry is fierce.
Alex
Anecdotal evidence is useless. Instead, let me give you a link. This discusses the effects of fast charging on smartphone’s batteries:
https://www.androidcentral.com/xiaomis-200w-charging-isnt-bad-battery-health-you-might-think
The batteries in current power tools are similar and are affected by similar processes. There is a definite decrease of battery’s lifespan with faster charging and it’s up to individual person whether they want to charge their battery slower or faster but with decreased lifespan.
Anson
Eight minutes would be a charge rate(C or Cr) of 7.5 (1C=60 minutes), recommended charge rates are between 0.5C(120 minutes) to 2C(30 minutes) for most batteries lithium batteries.
https://www.power-sonic.com/blog/how-to-charge-lithium-iron-phosphate-lifepo4-batteries/
In the above link they’re using a charge rate of 0.4 because the batteries are suggested for replacement of sealed lead acid batteries for long term use.
Here’s another link detailing a test to charge a LiFePO4 battery at 4C. Hopefully this helps demonstrate the diminishing returns.
https://www.homemade-circuits.com/lifepo4-battery-charging-discharging-specifications-advantages-explained/
Ice Road truckers driving at 1C/2C would be considered the speed limit(25-45mph) while driving at 7.5C would be driving 80mph, at that rate damage to the ice will occur.
Big Richard has additional information and a link about charge rates, it’s good.
Lance
It’s not a question of whether or not fast charging decreases a battery‘s lifespan, it’s about how much it decreases the batteries lifespan. People fall for clever marketing all the time and this is no different.
Milwaukee stating that fast charging batteries does not affect their lifespan is a lie. Is the amount of accelerated degradation significant? That is the question, and that is the data they will never share with their customers choosing instead to hide it behind marketing.
There’s a good chance that the trade-off is worthy, and the effects are not significant for most people, but come on… don’t treat your customers like they’re stupid.
Anson
Their statement is “No, there won’t be a difference in lifespan of batteries between standard, rapid, and super charger.” – As the rated lifespan is 300 cycles before it stops working (2-3 years depending on sku), that’s the statement to be evaluated as true/false. The statement is not about if it causes damage to the cells.
More battery cell manufacturers provide their data sheets on the web than do not. Battery re-sellers typically display less information.
If you open your battery packs and check for manufacturer marks you can go look up what the expected cycle data actually is. They’ll often provide the number based on the number of full cycles. Partial cycles don’t wear as hard as full cycles so 2x 50% is not equal to 1x 100%. Often including a rated capacity, i.e. at 1000 cycles you can expect XX% of original rating.
If you’re tracking the exact percentage and discharge rate of your batteries then the tool builders data of their test cells could be used, otherwise there isn’t enough data correlation to make a comparison.
Dewalt and Milwaukee have talked about battery wear on youtube factory tours. Using a high drain tool causes more damage than any other aspect. (Concrete saw)
When a review drains the battery in 10-30 minutes that’s far harder than the charger will push it.
For lithium cells once it’s manufactured it starts aging, cells lose maximum capacity even sitting, that’s why when Project Farm does tests they compare the batteries used against batteries that have been shelved so they can minimize discrepancies.
It wouldn’t surprise to see “Marketing” asked for the numbers from engineering and the 300-500(milwuakee and dewalt) cycles they reference seem low compared to the cell data sheets. The manual says that’s for the battery pack. That’s not a guarantee of 300 cycles at 100% of rated capacity.
Look at papers and articles about “Battery Aging and Characterization”, their are volumes of information about cell charging and discharge profiles out there. The candle power forums have HUGE amounts of information about various lithium cells.
Ken
Not even a good comparison , phone battery/ tool battery. Reason fast charge kills a phone battery is no cooling. Some phones here lately do have a heat sensing technology.
J. Newell
Exactly. With mobil devices, faster charging is almost always just applying a higher rate to the same cells charged under the same conditions. There are a few chargers with active cooling, but none are sold by the major major mobile device manufacturers, and AFAIK there are no well-conducted tests that show that there’s any advantage to the fans that some third party chargers have added to chargers. As a guess, it’s unlikely that these fans help much, if at all, when charging a battery that’s packed tightly into the device and then in most cases further insulated with a case.
The rapid chargers from (for example) Dewalt and Milwaukee have fans that provide active cooling. And, at least in the case of Milwaukee, the rapid chargers also detect battery pack type and won’t rapid-charge any M12 pack or the earlier M18 packs.
I don’t recall seeing any testing on this issue, but I have wondered, especially with the bigger Milwaukee packs, whether the rapid chargers might *increase* battery life by charging batteries at cooler temperatures for shorter periods, even though they’re charging at a faster rate.
As so many others wrote here, the tool manufacturers have huge motivations to get charging (and battery design, especially heat dissipation during both use and charging) right. If Makita introduced a new battery design or technology and suddenly Makita users on jobsites were seeing poor charging or runtime performance, word would get around very quickly and there’d be reputational damage that would translate to market damage (volume and pricing) that would take years to turn around.
Wayne R.
I always wonder why these companies don’t do more to cool the cells when they’re charging. Not suggesting an internal fan, but better ventilation? Heat sinks?
None of the batteries I’ve ever looked at had any apparent cooling features. Does that still hold on the newer & bigger batteries?
I understand that there would be arguments against that for compactness & cost. But still, design a fan into the charger to hit some internal cooling fins somewhere? Do it right and maybe charging speed can increase, and turn it into a selling point…
MM
I think that better cooling technology of some kind must end up being developed. There’s the obvious push to put battery power into more and more applications: OPE, riding mowers, and even small construction equipment. One huge problem with that is battery charge rates. It’s no big deal to fast-charge a typical cordless tool battery because there’s just not that much power in there. But a battery pack large enough for a big commercial riding mower, cement mixer, a big backpack blower, skid loader, logging saw, etc, is going to take far too long to charge off a charger limited by a normal 110V outlet. A homeowner can spend days charging his electric ZTR mower before using it on the weekend, but a commercial lawn service needs to be able to get a full day’s runtime out of an overnight charge. Someone is going to have to come out with a high current charger running off 220V before those larger tools become practical for commercial use. And that kind of charging rate is only going to be possible with some kind of cooling of the pack.
One technology I have seen used by people racing radio control boats is to layer aluminum or copper plates between each of the pouch cells in the battery pack. Sometimes there are water cooling tubes running down the edges of the plates, or in other cases the plates are oversize and stick out between the pouches acting as a finned heatsink with no water passages.
Sean
I think EGO batteries are notable for their cooling-centric design; for example, the way they spread the cells out in a U-shape to maximize surface area, the phase-changing material the cells are wrapped in, and how the vents are placed so that the cooling fan of the tool (and maybe the charger?) draws air through the pack.
I believe Makita also has fans built into some of their chargers.
My guess is that other factors outweigh heat when it comes to charging speed, so most manufacturers won’t bother until heat reduction becomes a larger bottleneck.
Stuart
EGO batteries are pretty cool (no pun intended). I don’t know if it’s just the higher capacity batteries, but they also self-discharge to ~40% storage capacity after ~1 month of disuse.
Jamis
Ego has stated their 56 volt packs are good for 1,000 charge cycles. I have yet to see other brands go out on that limb.
Jamis
FWIW, I have 3 18 volt Ryobi One+ 4 ahr. packs that are 13 years old and 2 6 ahr. packs that are 6 years old. They have all been charged on a Ryobi rapid charger. None seem to have any degradation as far as run time, but no documented number of charge cycles except I use them in rotation. I also have five of the 40 volt packs that are being used in a snowblower, but they are all new this season. I have 2 rapid chargers for these, so we’ll see how well they perform.
Andrew
If the charger and cell communicate during charging the heat Can be controlled.
Suggest you speak to Makita as they have intelligent chargers.
Robert Joe
My Makita Track Saw came with two batteries and a charger. The charger is dual port and has a cooling fan built in. My other tools are Dewalt and I two chargers. One is higher amps. I just use the lower amp one if I am in no rush. Again not sure if it will make a difference in the long run. For my phone, I never use a fast charger because the phone gets noticeably hotter and that can’t help with longevity…
MM
The existence of the fan on Dewalt (and presumably other brand) chargers is proof that the charger can detect the state of the battery and adjusts the charging current accordingly. Taking the Dewalts as an example since I am most familiar with them, there is an LED on the charger which indicates if the charger is operating at a slower than normal rate because the battery is too hot or too cold. The models with fans switch the fans on and off as needed based on what the charger detects from the battery as it is charging.
Given that I can’t imagine that fast chargers would damage batteries–they are capable of measuring the charging process and will slow down and shut off as needed to prevent damaging the batteries.
Big Richard
I don’t know that damage is the correct word. Reduce the overall number of cycles and/or impact charge potential? Yes, however slightly, it is still yes. There are so many variables that also contribute though, like depth of discharge (most important), storage conditions (full battery stored in high temps is not good), even charge level (charging to only 75% versus 100% can retain charge capacity longer over mores discharges.
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries
As a general rule of thumb, I try to charge at 1C (1:1 charge rate to battery capacity) or less. So a 2Ah battery I am going to charge on a 2A charger, a 5Ah battery I’ll throw on the 4A charger, etc.. Now, the further you discharge the battery, the more important this is. I never like to run them dead. I’ve got something like 12 different battery platforms and I don’t know how many dozens of batteries, but I have never had a premature failure from any brand. I work my tools hard, but smart.
Joellikestools
I thought my collection of six different battery types was a lot. 12 is a lot. What are the advantages from the variety?
Big Richard
Two or three of those are literally only one tool, and it’s just a goofy one-off tool that is not available on other platforms.
Otherwise it is combination of things. It’s not so much of an advantage, sometimes it is buying the best tool for the money, for the job. If there is a really good deal on a good tool and I have a need for it and can justify it, I’ll buy it, regardless if I am already invested in that platform or not.
Jared
I can’t fault your battery health regime, but I imagine less fastidious users are wondering something different about the trade-offs…
E.g. if using the “fast” charger means a battery can be used 200 cycles before there is noticeable deterioration versus 400 cycles with a regular charger, that might persuade me to use standard charges except in times of need.
If it’s 375 cycles versus 400… that is a different story.
Big Richard
No doubt. Depending on the user, the amount of time and energy expended pampering those batteries may be more than the cost of a new battery due to shorter lifespan. I can say I am a little more reckless with the compact batteries than I am my 12Ah batteries for that very reason.
Derek
I just realized one of my two Dewalt chargers is faster than the other. Don’t think it’s even been plugged in yet.
I picked up one of these so I can leave the batteries in the charger, hit 30 or 60 minutes on the timer and walk away.
https://www.amazon.com/Century-Digital-Countdown-Repeat-Function/dp/B01D3QEK4E
MM
The timer is entirely unnecessary. The chargers shut off automatically when the battery is done.
Adam
It would be a negative influence if the battery never charges to full.
Tim
That’s a backwards statement. It’s detrimental to charge to 100% as far as wear cycles goes, you get far more cycles of charging to 80% and in no way hurts the batteries.
Jeremiah McKenna
You do realize that Milwaukee, DeWalt, Ryobi, Ridgid, FLEX, and the other namw brand chargers of the last ten or so years don’t actually charge your batteries to 100%, right? Once they hit their approximate 70% level, they slow down their charging rate until around 80-85% and then if you keep it on the charger, they allow the battery to drain a bit, but still only charge to said limits.
The batteries also have a fail safe limit to the discharge levels. So when your battery stops turning the motors and blinking, they aren’t actually fully discharged.
Derek
It’s not to stop them from charging but just an added layer of security in case something goes wrong with the charger the battery doesn’t catch on fire.
Unnecessary but the $12 helps me sleep better at night.
Mxx
Let the battery pack cool down before charging on the slow charger. Including the 8s and 9s. Hide the fast charger.
Dave P
Our time is worth more than getting a few more charges from a battery. LOVE the rapid chargers…
Saulac
An opposite question: are there charger that extend/restore batteries. All my M12 chargers are the same. I have 5 or 6 Dewalt 20v chargers and they are not all the same. I know I do not have any fast charger (yellow?), but I have one charger that will charge batteries that other chargers could not. I know lithium batteries does not have memory…but wonder if there is any maintaining or restoring charger that I should cycle me batteries throught.
Big Richard
Sometimes if a battery’s voltage has dropped too low, or there is a bad cell, higher output chargers will not charge them, but a low output charger will. That could be your case. DeWALT’s DCB107 1.25A charger can bring some “dead” batteries back to life.
Stuart
Not that I know of.
But, as Big Richard said, some chargers have different low voltage thresholds.
I have been able to charge otherwise dead batteries with standard chargers when faster chargers didn’t work.
Saulac
Yes. That is my case. I forgot to mentioned that those batteries tend to be older or when I tried to make a few more cuts… I also use the battery-to-battery jump start trick successfully when I let the voltge dropped to too low to no bar. The jump start is simple to do and very effective. I exchange a few Dewalt 20v batteries under warranty before I knew the trick. I am pretty sure now that those batteries were fine and just needed to be jumped. TBW, I done it via local Dewalt service center. They just exchange me new ones, no question asked. Why no charger have this resurrection mode built-in? Do brand worry that people, like myself, will abuse it? Ha ha…
Tim
Batteries which have deep discharged have grown dendrites and are dangerous unless you have a charger which monitors internal resistance and temperature, just monitoring temperature isn’t enough when dealing with damaged batteries.
Rog
The Makita charger has a built-in fan to cool the batteries while charging. Not sure how much help it is overall but I imagine it’s better than no cooling
Tator
Ego has this feature also, plus ventilation holes in the battery packs themselves.
Hon Cho
The magic sauce of battery chemistry, charging rates, discharge rates , discharge depth, temperature ( storage, charging, in-use) make it darn hard for end-users to know and implement the best strategies for maximizing performance over each battery’s life . So, we rely on manufacturers to sell us products that are consistent with their performance claims. I’ve resigned myself to consider batteries as consumables they are and just use them until they don’t work for my needs. I believe Milwaukee and DeWalt both have three year warranties on their batteries, which is pretty generous. I have no experience with battery warranty claims so I don’t know how much hassle it is to get warranty service on a faulty unit.
MM
This is clearly true, but I can’t help but wonder how much “battery life maximizing strategies” actually matter in the long run?
I am still using many of the batteries from when I first jumped into Dewalt 20V max back in 2013. In fact, the only batteries from back then I have taken out of service were not due to electrical problems but rather mechanical failure from the packs being dropped onto concrete. I leave my batteries sitting on chargers for days. I have a relative who uses Ryobi OPE and they keep their batteries on the charger 24/7 in a non-climate-controlled garden shed in Texas. It freezes in the winter and in the summer it’s well over 100F in there all day long. Those batteries are going on 5 years now and still work well.
Now I’m not claiming that those are best practices for battery longevity but it seems fairly clear to me that modern batteries honestly don’t require much thought. Like Adam wrote back at the top of the page I think the manufacturers know what they are doing and “fast charging” will not do appreciable harm to the battery.
Jared
This is basically my feelings on the subject.
I put my batteries on the charger and take them off whenever I remember – or next time I need one. My batteries are stored in my unheated garage. I use them until the tool stops. I store them fully charged.
I know the conventional wisdom says none of that is “best practice”, but all my Li-on batteries are still in service even though several are getting pretty old.
Fast charging, when the manufacturers are telling you it’s fine, the chargers have active cooling and there’s no demonstrable evidence of a significant impact, just doesn’t seem like something to keep me up at night.
Munklepunk
Your description of how much effort tool companies put into battery tech is just another reason to not buy knockoff batteries.
Philip
Milwaukee HO tools and the HO batteries are at high risk of failure.
Type “AGREE” if you have experienced a Milwaukee HO battery failure. Type agree if you regularly trip out the batteries .
We need your input to see just how systemic the problem is. If you disagree… state what HO tools you use and the capacity you use them at.
Andy Ringsmuth
I don’t know if it helps or not, but on my Dewalt batteries, if they are noticeably warm after using them for a high-drain task and I need to charge them, I will literally put the charger in my garage fridge and run the cord out the door.
I figure it probably can’t hurt.
Big Richard
I would not recommend charging them in a fridge or any environment where ambient temperatures are less than 40F, that can really damage the cells.
https://www.dewalt.com/dewalt-dna/featured-articles/best-practices-for-battery-life
Stuart
I agree about not charging a battery in freezing/sub-40°F temperatures.
User manuals typically have recommended temperature ranges.
That Dewalt article reads as if it was never updated for Li-ion batteries.
JR Ramos
It really depends on the pack and BMS as well as the charging procedure in the charger’s chips. The cells will warm during charging and a good charger design can monitor various aspects and adjust current appropriately…some better than others. In this case it would hopefully not allow higher charging currents if the pack temp sensor indicates it’s below a certain temp…and then raise it once or twice as the temp increases. That’s perfectly fine. Lower current charging is fine even at quite low temps although it does increase “wear and tear” a smidgen and you may not really get a full termination charge. Depends on the electronics.
JR Ramos
i.e. ambient temperature vs. actual internal cell/pack temperature. Just because it’s 40F or 20F doesn’t mean that a charger can’t do its job safely and correctly in those ambient temps. It does need to do it intelligently, though.
Dave
I run my batteries hard and slap them on the rapid charger the instant they quit. If they will fail, I’d like to know it before I invest more into battery powered tools & equipment.
MFC
Milwaukee techs are full of bologna. They’ve all drunk the Kool-aid or been forced to. The fast charger does kill batteries. I used two 12ah batteries, one with charging on the rapid charger, and one on the standard charger. The rapid charger killed my 12ah within 2 years, although I was able to get it replaced under warranty. I don’t use the rapid charger anymore unless it’s an emergency. I have been charging 3ah, 5ah and 2 ah batteries on standard chargers for half a decade with no issues.
Heat = Death to batteries
Cold = Death to batteries
Either extreme is bad.
Xrh07
0 chance a 6A rapid charger kills a 12.0 due to charge rate. That’s only a .5C charge rate. Which is overall slower than a 5.0 on a 3A charger. (.66C)
If your batteries are getting “killed” it’s probably the tools overheating the packs and killing the cycle life. Not exactly surprising with Milwaukee though since they’re hellbent on shipping tools that need 90-100A battery packs.
bj
I think Makita only has one 18V slow charger (DC18SD) that comes with their lower cost kits – everything else is rapid. I’m just a DIYer, but I do have 15 batteries in rotation. I think two batteries are dated 2009 and can still take a charge, albeit with reduced capacity. I can’t get myself to throw those out since it’s still good enough for my low draw tools (lights, radio, USB charger). There was a third battery (2009ish), but that one died several years ago.
Unlike some of the users here, I have found that my Makita batteries have very low self-discharge. I never felt the batteries in my “charged” queue were deficient in power and the ones with BLI always maintained 4 bars (even after two months).
Stuart
Regarding self-discharge, are you using the ones with battery fuel gauges? I have found that Makita 18V batteries that have battery fuel gauges do self-discharge over time, even until they’re completely dead. I have not experienced this with other brands. Dewalt’s USB adapter will do the same to batteries if they’re attached and idle for long periods of time.
MM
I have noticed that some 3rd party battery adapters have built-in USB power sockets. This will also drain batteries if the adapter is left connected to the batt even if there is no device plugged into the USB socket. I have removed that feature from two of my battery adapters because it’s something I never use and I’d rather not have to worry about the battery running down to nothing just from being left connected to a tool.
bj
Off the top of my head, I have around 11 batteries with BLIs (battery level indicators) or fuel gauges. Unfortunately, my experience differs from yours, but maybe we need to clarify “over time.” I’m not a professional in the trades, so at times, my batteries can sit on the shelf for a while (especially my 2.0Ahs). The batteries that are not in my fans/vacuums/lights are charged, removed, and left in section of my shelf allocated to fully charged batteries. And while I don’t dispute the fact that it is self-discharging, I have not found it to be noticeable for my usage. For sure my Makita USB adapter will drain batteries when idle, so I turn those off or disconnect from my battery (older model did not have an on/off switch). Again, just my experience.
Tim
I can vouch for Rigid batteries with BLI, they do not self discharge. I’ve had a 2Ah and 4aH sitting around for months with 2 bars showing on the meter and they have not discharged at all.
JR Ramos
Self discharge is a normal part of aging of the cells but it’s especially noticeable when they have deteriorated due to high discharge down to low voltage levels and/or have been allowed to sit for awhile at a low state of charge. Generally it’s not too bad but if it’s really accelerated then the cells can become dangerous during the charging cycle if the BMS/charger isn’t a good one (more than just temp sensing).
Most BMS boards in packs will have some level of parasitic drain as well, although it’s very small. I’ve not bothered to check pack voltages to monitor the way I do with individual cells for lights and other devices, but this small drain is almost everywhere – more or less drain depending on the engineering design of the circuit(s). Some packs don’t have this on in the pack, but rather in the tool body (or can have both).
For well used packs, it’s just normal, though, and eventually they’ll be too tired to charge or hold a charge. The indicator lights don’t always tell the whole truth, either…sometimes more truthful on an in-use pack as opposed to one that’s been resting for awhile.
David
Has anyone had problems with the hd12amp not discharging fully?
Phil
If/when you have multiple batteries (as most do) the need to “fast charge” is redundant and unneccessary. as such, whats really happening is people don’t recognize they simply have bad habits/bad desires. I have 2 Milwaukee fast chargers but I dont even use them. in contrast, my buddy uses his Milwaukee fast chargers (though he doesnt need to) and last week he informed me many of his 12V batts (approx 3 years old) are no longer holding charge/giving normal run time during use. by comparison my 12V batts are going on 7 years old. he just orderered 4 new batteries. translation: SLOW CHARGING FOR THE WIN.
Bob Voss
I received a Milwaukee bare tool m12 work light as a gift.
It said only to only use the m12 charger I went to nearest Home Depot, (50 miles away) and found the $99.00 battery/charger on sale for $69.00, (saved the gas money and signed up for their NEW Veterans discount which same the tax.) I bought other things I needed and was very happy.
I read the directions and opened the plastic packaging with difficulty ,then let it set overnight in my 72° dining room.
the next day I charged it, but only got the defective battery red and yellow alternating leds signals over and over,(did not get hot), my wife has the same m12 battery in a heated jacket and the battery I bought charges fine on USB, meaning the charger pack is defective and requires a 100 mile round and getting another battert / charger. I have never bought Milwaukee before and after the battery pack, probably never again..) I usually shop at nearby Lowes, (which has had Miltary discount for years and have it on my no e credit,, MY LOWES card, which records all my purchases.
.
JR Ramos
My apologies for not thoroughly reading all of the comments, but my opinion is that this greatly depends on the BMS and on the individual cells chosen for the pack. In general, these high current/high drain cells in tools are quite robust in terms of the current/heat they can handle, and that works both directions. Discharging generally creates far more heat in the cells/pack than fast charging, and frankly none of the fast chargers on the market even approach the acceptable high rates that manufacturers state their cells can handle. But fast discharging and BMS logic that might allow discharging at higher currents/voltage sag down to lower voltage levels is what will really put the hurt on cells and vastly reduce their cycle life as well as their operating capacity during that time (mostly by increasing their internal resistance, which snowballs into heat).
That said, slower charge rates are always best practice if you’re interested in eking the longest life out of cells. This is true for individual cells or cells in packs. If a charger sequence allows for a slow “identifying” time period followed by a ramp up to a high charging rate, followed by a longer tapering off of current for termination…that’s the best approach for these cells. They can handle the high current and that’s fine for filling up the glass until it’s close to full, but terminating carefully/correctly is important (just as not draining them too deeply is equally important).
Not all cells are the same. I’ve disassembled a number of packs of my own and that I swiped from the recycle bins at the box stores just for an explorative look (and to harvest some cells that are still good). The variety of quality and performance of cells used in packs – even from the same brand – is rather wide. It’s maddening because the per-cell cost difference between some of the cheapies vs. leading cells is very minimal *especially* for the retail price they are charging for these packs. It’s ridiculous but the pennies do add up in volume and design budgets must be met. This is to say that Cell A in Brand X’s pack may do fine at a 5C charge rate or more, but Cell B in some other pack may not like that as much…so the charging sequence and such needs to accommodate the cells in the pack. Other than that, fast charging isn’t necessarily bad at all like it could be with early (or ultra-cheap currently available) lithium cells and nothing at all like the comparative wimpiness of NiMH (old NiCd was actually a little better in this regard but then there was the “memory” issue to cope with).
One of the chief limitations here is heat, as so correctly mentioned right off the bat by Stuart. This is compounded greatly by the insulative plastic housings the cells are surrounded by (and sometimes further compounded by cell holders that increase this insulation). I don’t currently own a fast charger but would have no concerns using one again for my Milwaukee or Bosch packs. My approach has been to have more packs available and try to not run them down so low before charging, and just let the slow charge do its thing. But I really think discharging is the big killer…certainly has been for a few of my Milwaukee packs (it’s a pain to get them warranteed but they’ll take care of it…slowly).
The cooling (ambient or forced) in a charger is just for the chips on their boards. It does little to nothing at all for the packs themselves. Standard utility/hobby chargers are the same way although individual cells in individual bays suffer far less from heat even at high charging rates.
JR Ramos
As a side note, there has been recent published research that suggests some higher current/voltage “zapping” of lithium-ion cells while charging shows an ability to reverse some of the dendritic “aging” in the magic sauce. It actually looks like a useful discovery – believe it may be targeted more for the automotive market if it comes to fruition but it should apply to all lithium cells (I think…not sure if cylindrical jelly-roll cells would be different than pouch cells but probably not). If this has commercial merit then perhaps we’ll see it trickle down into charging algorithms and sequences, which could go a long way toward extending cell/pack life and maintaining performance before the lithium finally does give up. Most lithium/battery research ends up being pie-in-the-sky stuff and never sees application outside of the lab research and such, but this one seems like it shows great promise.
Kevin
I’ve done a lot of work with battery technologies. In the case of the ubiquitous lithium ion battery chemistry, the short answer is no, they don’t have any sort of appreciable effect on lifespan of the cells, and in turn the pack as a whole. The notion that rapid charging these batteries somehow shortens their life expectancy, which is akin to a modern day wives’ tale. While generally true on a very basic level that increased rate of charge can “wear” a cell more, it’s simply not the case all things considered. All things being equal, the idea is a higher rate of charge, greater energy delivery, generates more heat, which is what lithium can act adversely to. Heat is what harms batteries that are based on lithium chemistry, not simply the rate you charge it. However, they implement countermeasures to mitigate the excess heat associated with higher charge rates. I’ve torn down the super charger and they do a more than Ada quart job of managing the thermal conditions. Not only do it the charger actively cooled via fan, the fan directs airflow through a huge heat sink. I haven’t measured the temperature but I’d be willing to wager it runs nominally cooler than the standard charger which has no active cooling obviously. As long as you can mitigate heat, the batteries don’t care how much current you deliver to them.
Pete
Assuming someone is charging $100 per hour for his work and a battery costs $100 and you can fast charge a battery in 30 minutes vs an hour in slow charge then it takes 2 charge cycles to buy a new battery.
Does the discussion of reaching the spec defined 900cycles of a battery makes real life sense? Not for me.