The US CPSC has announced a recall of Skil 40V 5Ah cordless outdoor power tool batteries due to an overheating issue that poses fire and burn hazards.
According to the notice, there have been 100 reports of “thermal incidents,” such as overheating, melting, smoking, and fire.
There were 8 reports of minor burns and/or smoke inhalation injuries, and 49 reports of property damage.
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STOP using the recalled Skil 40V 5Ah lithium-ion battery and contact Skil for a replacement or refund.
Chervon, Skil’s parent company, will provide registered affected users with a battery collection kit and instructions on how to return the battery.
The recalled Skil battery was sold separately and as part of kit bundles with select cordless mowers at stores that include Lowe’s, Amazon, and Walmart.
According to the CPSC, about 63,000 batteries were sold in the USA, and 359 in Canada.
The recalled batteries was sold from October 2019 thru December 2024. There are 12 affected manufacturing dates – you’ll need to check your serial numbers against the list to see if your batteries are included in the recall.
This image shows you where you can find the serial number on the 40V 5Ah battery, and which 3-digit date codes are subject to recall.
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Recall Number: 25-071
Thank you to Jason for the heads-up!
Jared
I didn’t know there was a 40v line from SKIL. Sounds like the rest of Canada didn’t either.
Rzorrok
I have some of them. The mower is OK, not great, but the chainsaw and pole saw are both excellent.
Mike
Chervon makes both Skil and Ego brands. I have an 8 year old Ego mower that is still going strong. Bought the Skil as a second mower. Although not as robust as the Ego, wife and daughter both like the mobility and lighter weight of the Skil. Battery is not one of those recalled.
frobo
Thanks Stuart, I have a couple of these (and another one on order). I’ll check out the serial numbers asap.
eddiesky
Weird. I wonder, unrelated but weird…this morning I saw a flashing green aura in my living room. I forgot I had relocated the EGO charger and battery from garage (getting cold out and garage not heated)…the battery which is fully charged…would just flash intermittently. It was not on the charger. I hit the button on the battery and it did the segment rotation till all 5 segments lit and then out.
Almost need some Battery Box to store these in that could contain an errant thermal event. (Battery fires in laptops and devices are/were called Thermal Events in my Apple tech repair days)
*I’m reaching out to EGO about their battery weirdness as this is concern..might be nothing but thanks for post on the Skil batteries…
What are thoughts on proper battery storage? I could see cheap knockoffs being a problem but what about Milwaukee, Dewalt, Bosch, etc ? Should a market exist for storage that is metal, ventilated with ability to seal off with thermal sensing? Or like chem-storage lockers, have firehose input bung?
Doresoom
The EGO batteries flashing green is normal. After they sit in storage for a while they will automatically discharge to about 60% to optimize battery longevity.
Stuart
30%. And they flash red, which can be concerning. It’s so annoying, but makes sense since EGO batteries are used for seasonal tools with not much purpose over the long months in between.
Saulac
Want to learn more on this lifetime optimization. I thought the day of charging level and storage was behind us. Recently reading something about NOT getting the battery fully charged to extend the battery life on a Ring door bell and was a bit surprised. Is this a Lithium battery characteristic or more with cheap circuit board some batteries may have?
Doresoom
It’s true for all lithium ion batteries.
Stuart
How do you feel after you eat a meal and your stomach is at 80% capacity? 100% capacity where you cannot possibly eat another bite?
Battery management gets complex and decisions are made at the engineering level.
My Sony battery charger has a setting where it can do a normal charge or full charge. If you need the longest runtime possible for a project, opt for the full charge. Otherwise, normal charge is said to prolong battery life.
There are no hard rules.
A DIYer in a mild area might use a cordless snowblower 1-4 times a year, and expect the battery to last 10 years.
A PRO user might use a cordless vacuum every day and run through multiple battery charge cycles in the process.
Most brands are going to make decisions that improve customer satisfaction.
Nate
BatteryUniversity has a ton of detail.
Basically, every other chemistry (lead, nickel) wants to be at 100% charge. Lithium is different, and degrades rapidly when held in a high voltage (fully charged) condition.
But manufacturers want to rate their cells with the highest capacity, so they push the voltage up. Arguably, what they consider “fully charged” is considerably overcharged, if you look at what’s actually happening on the electrodes.
So lithium (both lithium-ion and lithium-iron-phosphate) does better if it’s not fully charged. Yes you get less runtime out of each charge cycle, but you get tons more cycles because the cells just don’t degrade. If you can operate a lithium pack between 20% and 80% state-of-charge, yeah you’re only getting 60% of the rated capacity, but it’ll last 500% as long as one that’s cycled between 0% and 100%. The payoff is enormous.
However, the trick is that packs are made of many cells in series, and the cells aren’t precisely identical. They can go out of balance after a while, and most battery management boards perform what’s called “top balancing”, where the pack is brought to 100% and then then strongest cells are slowly discharged while the weaker ones catch up. This is necessary at least once when the pack is new, and it’s probably a good idea to do it once in a while thereafter; annually is probably plenty.
So, all my packs have 4-LED capacity indicator, which really just reads the pack voltage. I try to pull ’em off the charger at 3 bars, not letting them get up to 4. And I try to stop using ’em when they get to 1 bar, not letting them get to where they shut themselves off.
As a result of this gentle treatment, I have packs from 2013 still in service and performing at a significant fraction of their original rating.
JR Ramos
It isn’t a huge deal, as Stuart said. Yes, you do get some longer cycle life on paper but whether or not you can actually benefit from it in a tool battery pack with electronic controls that often kill them off too early (aggressive safety stance for high drain use with several cells in series…) is dubious.
Battery University that Nate mentions is an excellent (and exhaustive) site, well worth spending some time there reading and learning. Some of the information is pretty dated but mostly still accurate. What they say about full charge (which is actually a state of max overcharge) is still true but their info was mostly coming from older cell chemistries. The ones used today and notably the 21700 cells are more robust and can tolerate a lot more “abuse” in various ways without suffering the same amount of “damage.”
For small cells like in your Ring, if you don’t mind recharging more often then yeah, you could do that and probably see more benefit. Limiting the top end charge to something like 4.1v or even 4.0v instead of the full 4.2v doesn’t lose you much capacity especially in low drain applications like that. In high drain applications like power tools, that tenth or two of voltage disappears in mere seconds anyway. But on the flip side, with the full standard charge on a low drain Ring camera, you will enjoy a bit longer use between charges, just maybe at the expense of a few dozen cycles lost and perhaps reduced capacity a tad earlier than expected. Small cells show these minor differences more than larger typical round cells do.
I have no idea what they may have going on with their control circuits, but those usually do govern a lot and can alter basic cell characteristics/practices enough to make it a different animal almost. Experiment if you want…take notes, see if anything matters to you between the full charge/slightly less charge. It’s really just the duration of heat toward the end of the charging cycle that is causing any slight damage…heat hurts most things…true for NiMH cells as well (and old NiCd but for all the shortcomings of that older tech they sure were robust and hard to truly hurt until they were really spent).
Good examples of abusing cells the wrong way are things like the Dyson packs and Milwaukee’s choices with the M12 6.0Ah packs. Both of those just have waayyyy too many early failures and lifespans because they push them like Tesla. lol. Your camera will never be so harsh even on a busy day.
If you really want to less-than-max-charge your batteries that may take a little work on your part. You could get a very expensive hobby charger that will let you set the parameters, but most basic battery or device chargers just let it go until it’s done and don’t have any indication of what the voltage is. You can pull the battery a bit earlier than the typical charge time is, measure the voltage with a meter, and adjust time from there. By the 4v stage the battery will probably be cooling off again but could still be warm (that last period to get to max charge is slow and tapers down…to get the best goodness that way and minimize a little of that full charge damage).
By the way, these li-ion cells are white-sheet nominally rated as 3.7 or 3.8 volt cells (depending on manufacturer and model…same difference). When we charge them to 4.2 volts it’s an overcharge, not a full charge. It’s safe, no worries, but that’s what we do. Storing them at a lower state of charge is good for long term, especially if warmer temps are expected like in a garage (or worse, a shed or a truck). Determining state of charge as a percentage isn’t a straightforward thing as the energy stored and able to be released isn’t linear along that voltage reading. By the time cells are down to 3.4 or so most consider them functionally dead for most applications and as you drop to 3.3 or 3.2 you’re just squeezing out the little that’s left (still adequate for low drain stuff like low power flashlights and some devices). Some power tools cut off the juice before it even gets as low as 3.4 (again, aggressive safety (that cell balancing Nate mentioned, but also user satisfaction so the huge drop in voltage that equals much lower performance in a tool doesn’t make users unhappy while they’re draining to that point).
But generally for long storage at room temp or a touch cooler, I think most have settled on about 3.4v as a good target, but 3.5 is fine and really even that nominal 3.7v isn’t going to hurt anything unless it’s above 80F or creeping into the 90s for months on end.
Every type of battery has had its shortcomings. The “memory” effect with NiCd….lower overall robustness and performance and lifespan with NiMH….and li-ion gives us great results at the expense of some slight safety concerns and needing to learn the care and feeding of something “new.”
Doresoom
Here’s the explanation, page 15 of the manual: https://egopowerplus.com/media/productattach/1/9/19-0104_ego_battery_manual_na_v2.pdf
Jason M
More parent videos plz
Jason M
Patent*
eddiesky
Update: tis normal per EGO. The batteries when idled or left off charger will do a maintenance cycle. Per their support which I called.
eddiesky
LOL..you posted while I was on the phone! Thanks Doresoom!
Saulac
Been around those flammable cabinets since forever, love them ‘cause they last forever, and it never occurred to me those “caps” are fire hose inlets. Make perfect sense as you do not want to open the doors if it is burning. I had thought they are to connect metal pipes for ventilation to outside….but have never seen such applications.
MM
I have never seen a flammable storage cabinet with the correct kind of threads to allow fire hoses to be attached. I’ve worked with the cabinets for many years but those I have used have standard tapered pipe threads on them–NPT. Fire hoses use different thread standards and are not compatible without an adapter. Furthermore, the instructions for the cabinets I have personally purchased and installed refer to the connections as being for ventilation purposes. For example:
https://www.justrite.com/media/techtalk/TT-Cabinet-Venting_9-5-19.pdf
Some of these cabinets may well have fire connections, but I believe that most of those connections are intended for ventilation.
Stuart
Agreed – I’ve only ever seen venting for the purpose of ventilation. That’s part of the design intent, to reduce the buildup of ignitable vapors that can happen in fully-enclosed spaces.
On top of your link, there’s a little more here – https://www.justrite.com/safety-cabinets/ventilation .
will
The power tool companies need to follow the phone companies (oneplus,honor so Chinese companies) and us silicon/carbon based over lithium ion. They seem to be denser,lighter,run cooler and last longer per charge. They seem to handle speed charging better as well. This is relatively new tech as far as I know ,but would be worth a look. That is unless silicon carbon doesn’t handle high power draw as well. Either that or it wouldn’t be compatible with existing tools. Either way it’s time for a change.
Stuart
Phones sip energy. Power tools guzzle it.
JR Ramos
I may be wrong if the phone pholks are using something different, but the silicon approach has been in round cells for a few years now – not getting much attention or good reception, however. The Samsung 50S 21700 was the first out and while it could handle a moderate amount of current *with* a nice high capacity, the poor things just fall on their faces and die early deaths much, much sooner than decent li-ion IMR or INR cells that are the norm. I can’t remember the numbers now but near their rated current delivery (i.e. not torture tested) they were losing well over 20% at a very low number of cycles (I want to say something like four times earlier than what we usually see with good li-ion). That 20% loss is an industry standard metric for cycle life performance and voltage maintenance. It dropped just as fast down to like a 40% loss in not that many more cycles. So it has some up front short term benefits but it comes at a significant cost in lifespan – that was true at lower currents as well as the moderate ones, and the torture tests that pushed them beyond rated delivery really snuffed them in short order, where other cells will handle that a lot better (still damages them all quickly, though…lots of heat).
Tabless was a much better leap for high drain applications like power tools, e-bikes, cars, etc. It’s the new black and hopefully will see wider production and economy-of-scale reduction in costs, then wider adoption by power tool companies. Assuming we don’t find ourselves globally in a lithium crunch in the coming years…..
ColeTrain
It’s amazing how we all daily think nothing of lithium. It’s easy to keep stable but just as easy for one minor mishap for it to show it’s true power. It is after all an alkali metal. The fact that it has the power to propel a 5,000 lb car to 60 mph in 3 seconds and we think nothing of it is wild… Yet we sleep with it inches from our face plugged into a power source. Just watch a video I was lithium reacting to water and you’ll get it, and yet many of us swim with our phones. LOL. Plus lithium can get in a self-heating state fairly easily and when that happens you have all the fires that you hear about. Hell I know better and I still ignore it at times. One thing people should know that don’t is when you’re lithium device is charged, unplug it. There is a zero benefit from leaving it plugged in. If it says 100%, it means 100%. There is no 110% with lithium batteries. Actually there is, it’s called a thermal runaway, AKA fire. How much do you trust the protection circuit in your battery?
Stuart
There’s caution, and then there’s panic. When driving down the highway, you are one turn off the wheel away from demise. There is inherent danger everywhere. The key is to avoid unnecessary risks, and simply take recommended precautions.
Batteries from reputable brands are thoroughly engineered and tested. Something went wrong here, and Skil hasn’t provided any details. But it at least seems like they’re cooperating with the recall.
Energy must be respected.
Random info: 240 watt hours, around the energy capacity of an 18V 12Ah battery rounded up, is about 206 calories.
Doug
Other brands must also be part of it. Batteries aren’t that unique and there aren’t that many manufacturers.
Think about how many batteries are out there now. Think about the future. We all have batteries galore and they’ll get old and they’ll get unstable and they’ll need to be disposed of. A Dewalt 5ah might be fine for 20 years but eventually I would think it will stop being fine. How old is old? How many charge cycles? What about disposal? How many of you honestly recycle all your batteries? Even if 1 in a 1000 is landfilled that a lot of batteries in our landfills.
It’s going to get worse especially EVs. Imagine when those batteries need to be changed. Nothing is regulating these batteries. Fires and explosions waiting to happen.
Stuart
The problem is with the Skill battery pack. Different brands might use the same or similar Li-ion cells, but they all tend to have different management systems.
Skil hasn’t disclosed what went wrong with their batteries, but it could be flawed or defective thermal management.
It’s like pasta boiling over in a pot. That’s not the fault of the pot or the burner, but a failure in oversight and control.
Nobody should be throwing Li-ion battery packs in the trash. So many retail stores offer recycling, such as Home Depot, Lowe’s, and Staples that it’s fairly easy and not too far out of the way.
Richard Fairlie
I have one of the batteries in the recall. It overheated and melted the plastic case and the charger case. I asked and they are only replacing the battery, not the charger. Luckily I have another charger.