If…the idea of using cordless tool batteries to power an ebike has ever crossed your mind? You are not alone. After some research, I found out that…it is not as crazy as it might sound.
First of all, I have known for a long time that the 18650-format cells that are in cordless tools (18650 = 18mm diameter, 65mm long), are the premium cells that you would want for making an ebike battery pack. Its true that laptop computers also use 18650-format cells, but…those are low-amp cells that compete on lowest price, not high-performance or long run-time. Just four years ago, pioneer ebike hot-rodders like Doctor Bass had to buy and gut cordless tool packs to get high-performance cells (now, there are hot-rod packs from many suppliers, like Luna Cycle).
So…this leads to a question. Which cordless tool packs can power an ebike? This isn’t a crazy question. International trade conflicts mean that at any moment, products from China can become a temporary casualty of a trade war (there is currently a trade deficit, meaning the US buys more from China, than China buys from the US). Trust me, all ebike products have some component that comes from China.
If there is a trade war, there will still be tens of thousands of cordless tool battery packs that are still in US warehouses. They will be waiting to be bought by construction contractors, but…if some of them are appropriate for our ebikes, right when you need one most? this article will try to help you identify which one are worth going out of your way to snap them up, before anybody else gets them.
First of all, we must limit ourselves to the voltages that are supported by common ebike controllers. The capacitors (inside ebike controllers) are the component that will limit the top voltage of the system. The common 36V, 48V, and 52V controllers typically use 63V capacitors. Then, the Low Voltage Cutoff (LVC) is what really designates what a certain controller is suppose to work with (some controllers have a fixed LVC, and others are adjustable), and an LVC is important, because you never want to drain the cells to zero volts. Sadly, I haven’t found any good lithium cordless tool options at 48V (13S), so…
If we agree on a low voltage of 3.3V per cell for common 18650 chemistries (3.3V for long pack life, as opposed to a more common 3.0V per cell), then…a 10S and 14S battery pack would have an LVC of 33.0V and 46V…respectively, (commonly called 36V and 52V batteries).
Ebike battery packs made from lithium 18650 cells are considered fully-charged to 100% when they are at 4.2V per cell, so…a nominal 36V / 10S battery pack will have a top-voltage of 10S X 4.2V = 42V, and a 52V / 14S pack will have a top-voltage of 14S X 4.2V = 58.8V. The cordless tool battery packs we are interested in have a top-voltage of 10S / 42V…and 14S / 58.8V, commonly called 36V and 52V.
So…where does this lead us?…if you are happy with 36V (10S) and 52V (14S), then…you DO have some cordless tool options for your ebike.
It is possible to get 36V (10S) from connecting two 18V (5S) cordless tool packs in series (in fact, several manufacturers do this for some of their tools like Ryobi, Makita, Black and Decker, along with Greenworks). I don’t think this will ever catch on for ebikers, and the only 36V / 10S packs that “might” find a few EV users will have a full 36V / 10S voltage in one single pack (plus one single charger, instead of two 18V chargers).
[This web-magazine is focused on ebikes, but…we also love power-boards. Most of those are using “Radio Controlled” (RC) components, and for good reason. That being said, common RC voltages are 18V (5S), 22V (6S), 28V (8S), and a few even use 36V (10S), or 44V (12S). If I was starting a power-board company? I would DEFINITELY use an existing cordless tool battery pack as my interface. Why wrestle with shipping compliance and warranty issues when my product can simply use a battery pack that can be found at any Home Depot, Menards, and Lowes hardware store? not to mention Ebay and Amazon ]
If you are interested in getting 36V by connecting two 18V battery packs in series, seriously consider the Milwaukee 18V / 9.0-Ah packs. In fact…if you are happy with 36V and 9.0-Ah…this would be my preferred battery pack, since the largest single 36V pack listed below is 6.0-Ah.
I don’t list anything from Ridgid, Skil, Festool, or Hitachi in the text below. Their lithium batteries do exist, but I haven’t found any worth mentioning for this type of application. Metabo and Hilti brands are high-quality and heavy-duty, but their batteries are only 18-volt and low-Ah, not to mention very expensive.
It’s my understanding that Milwaukee has purchased Ryobi and Ridgid brand names. It has been speculated that Ridgid is now their “affordable” brand, Ryobi is marketed as the mid-range home-owner “light duty” brand, and Milwaukee is advertised as their serious heavy-duty and high-quality contractor “use all day” brand.
36V choices (10S)
There are several cordless 36V tools that use TWO of their 18V battery packs (mounted in series) to achieve 36V (like Makita). That is good for the contractor who wants more power than 18V (while still using his existing 18V batteries and chargers), but…I don’t think the 18V batteries will be popular with ebikers. However, there are actually quite a few 36V battery packs, though…
[be aware, if you are buying cordless packs in order to cut out the cells and build your own pack? The smallest packs provide the most amps per cell, because in order to get the minimum needed amps to power the tool with the fewest number of cells, the small packs have the highest current cells. The 2.0-Ah packs often have only five of the Samsung 20R cells rated for 22A per cell in a 10S / 1P configuration, and the 5.0-Ah packs often have Samsung 25R cells in a 10S / 2P, rated for 20A per cell (2P = 40A total). The 6.0-Ah packs sometimes have the 30Q cell in 10S / 2P, rated at 15A per cell (2P = 30A), however…do your homework before buying any pack, and first buy just one to gut…before you buy ten of them]
Be aware, there are many 10S cordless tool battery packs (ten lithium-ion cells connected in series), that the manufacturer is calling a “40V” pack. Rest assured that all of the packs listed in this section are the same voltage, whether they are called 36V or 40V.
The Kobalt brand is the house re-branding name for cordless tools from the very large Lowes chain of hardware stores. The 40V Kobalt line has a 2.5-Ah, and also a 5.0-Ah size, the KB540-06
Ryobi products are typically found in Home Depot hardware stores. Their 40V line has a 2.4-Ah size of pack, a 4,0-Ah, and also a 40V 5.0-Ah…part number OP4050A.
The Stihl brand is very well-known as a serious gasoline-powered gardening tool maker, like chainsaws. Their 36V AP-300 is a serious 6.0-Ah. In this video below, the smaller AP-180 is shown “opened up” for a few seconds, showing that is has 30 cells in a 10S / 3P configuration. 3P providing 6.0-Ah means each cell is a 2000-mAh, which suggests that they are likely the highest amp-producing cells available, and…that explains why Stihl is getting chainsaw-levels of power from only 36V, the Stihl tools use very high amps.
The Troy-Bilt brand is listed as having a 40V 6.0-Ah pack, but…I can’t find any details about it so far. They want people to buy it, but I guess they just don’t want you asking any questions about the internal details…
The DeWalt 40V DCB404 is only 4-Ah (somewhat small), BUT!…the DeWalt 40V DCB406 is 6.0-Ah.
I saved the best for last, and if you really want to use a 36V battery pack for an electric bike? seriously consider the Bosch 36V packs. Not only is Bosch a very large global brand that has a reputation for using quality components, they are the only 36V pack that uses air-cooling. In our article on making lithium batteries last as long as possible, one of the key elements was preventing them from getting too hot. I’ve only found two brands that have this air-cooling feature, Bosch and EGO.
The Bosch charger definitely blows air through the battery pack when it is charging. I haven’t found proof yet that it gets powered air-flow when you are running the tool, but…their engineers are nuts if they didn’t do that. But…even if they don’t...the Bosch 36V / 10S pack system has a 6.0-Ah option for their mower, so…it’s at least as good as the other options above. If the 6.0-Ah pack is fan-cooled when it’s running, then it is the clear winner. At he very least, it’s construction allows an ebiker to add a fan to it, and the others do not.
Husqvarna and Craftsman are generally considered fairly decent brands, but…their only 40V packs are small (4.0-Ah, or less)
If you Google 36V and 40V battery packs…you will also come across the off-brand names Enegitech, Earthwise, Lynxx, Sun Joe, Oregon, and others. I have no experience with these, but I suspect they use some pretty generic cells with a cheap BMS and a cheap charger, so I don’t recommend them. If you try them out, please post about them on the internet (and send me a link), whether the results are good or bad.
Hilti makes a rock-solid 36V / 6.0-Ah pack made from only the highest quality components with a bomb-proof warranty, but…did I mention? Its over $420 for only one of them without the charger…yeah.
Conclusion for 36V packs
I do not consider 6.0-Ah to be a very big pack (for an ebike, at least), but…if your ebike can “get by” with this size, then…the 10S DeWalt, Troy-Bilt, Stihl, and Bosch all have a 6.o-Ah battery pack model available. Prices vary, so shop around…(don’t forget the option of using two Milwaukee 18V / 9.0-Ah packs in series)
I had really hoped I would find at least one cordless tool lithium battery pack that used 48V (13 cells in series, 13S). The few 48V devices I found (lawn mowers, etc), turned out to use lead-acid batteries. If you find any, please send me a link.
52V choices (14S)
This is the jackpot for cordless tool batteries being re-purposed as ebike packs. Before we get started here, a large direct drive (DD) hubmotor draws very high amps for the first few moments of acceleration. How high? well…how much money do you have? Speed costs money, and large DD hubs can take as much as you’ve got. I don’t recommend cordless tool packs for a large DD hubmotor…
However, mid-drives such as the popular Bafang BBS02 and BBSHD typically only draw 25A-30A when using the stock controllers. Their controllers will also run off of a 48V pack or a 52V pack. There are several selections listed here that will easily provide 52V and 30A. There are even small geared hubmotors that would be happy with 52V / 30A, without straining the battery packs.
When a pack with 14-cells in series is fully-charged to 4.2V per cell, the packs’ top voltage when hot off the charger is 58.8V. The nominal “average” voltage is commonly referred to as 3.6V per cell, so the 14S nominal voltage is 14S X 3.6V = 50.4V…
Some ebike 14S pack sellers call their packs 50V, and others call them 52V, but…if they use lithium-ion cells? They are all the same exact voltage. That would be 50.4V nominal up to 58.8V when fully charged. The internationally-recognized standard for DC voltage to penetrate dry skin is 60V. The starting voltage of these 14S packs just barely misses that, but…after only a few moments of run time, the pack will settle into the long “nominal” voltage portion of the discharge that is near a much safer 52V.
The Worx brand weed trimmer is listed as 56V, but it appears to be physically identical to the Echo 58V. There are teardown videos of the Echo battery (see below), but I haven’t found video of the Worx pack interior to verify my theory that they are the same.
These Echo packs are called 58V, but they are definitely 14S, so…they have the same voltage as the other packs in this section regardless of the voltage in the name. The Echo engineers wanted their packs to be as compact as possible, so they are mounted in a tight cube. That does make the pack small, but…it also restricts airflow through the pack, making the cells in the center of it warmer than the cells at the edges. Heat is bad, and it is very beneficial if you can avoid that as much as possible. It doesn’t matter how long the cells around the edge survive, if the cells in the center die an early death, the whole pack immediately becomes trash, amirite?
The largest Echo 58V pack is a modest 4.0-Ah, and this is another way in which their weed trimmer is kept to a very light weight, but…it also hurts the mowers run-time (they both use the same pack, with the mower using two of them, and the weed trimmer using only one). However, there are options, so…keep on reading below!
Buckle-up, because this section is going to be an earful. Fair warning, I am a huge fan of the EGO batteries. In the interests of full disclosure, I have never received anything for free from EGO, and I paid the full retail price for their weed trimmer and lawn mower, both purchased at Home Depot.
Not only does EGO use high-quality name-brand cells, they have done four specific things to keep the cells as cool as possible, which is why the EGO packs should last much longer than the other brands.
- Each cell has a PCM sleeve to absorb heat-spikes. PCM is a “Phase Change Material“, and the All-Cell company is famous for inserting their cells into a large block of PCM to help manage battery heat. With this type of PCM, it doesn’t change from a solid to a liquid, it’s more like changing from a hard rubber to a soft rubber, when the cell gets hot. During that process, it can actually absorb a surprising amount of heat. The heat still has to be dissipated over time, but this simple addition limits the highest portion of the working cell temperature peaks.
- Speaking of dissipating that stored heat that was absorbed by the PCM sleeves, these packs have an unusual shape that spreads the cells out, instead of bunching them up in a block. This helps air-circulation, which is vital for the next feature…air-fan cooling!
- These packs from EGO are not sealed, they have channels that allow fans to blow air through the packs when they are being used, and also when they are being charged.
- The last feature that helps these stay as cool as they can be…is their size. The EGO mower does have an UN-exciting 5.0-Ah pack available, but I opted for the 7.5-Ah, which is the largest cordless tool battery pack I have found (other than the backpack batteries listed farther below). A 7.5-Ah is not only the best range of a cordless pack, it’s size means that each individual cell is less stressed, and will run cooler than it would if you were pulling the same amps from a smaller pack.
Since these EGO packs require an open architecture to allow for the awesome fan-cooling feature, the electronics are all fully potted in epoxy against rain and accidental splashing. I’m sure the various brands of mowers and weed trimmers have a performance that all work about the same, but…it was the batteries that made me a fan of the EGO brand.
I now own a mower and trimmer, and I can verify that they are pretty damn great. I don’t need earplugs like I did with the loud gasoline mower, and it is quiet enough that I can get up early in the summer to mow, instead of waiting until later when it gets hot…and I used to do that so I didn’t wake up my neighbors who are trying to sleep-in on a Saturday.
One other great feature is that I own two 52V ebikes, and…when they get to being several years old? their capacity will eventually erode down to 14-Ah from the original 17-Ah (as all batteries do, regardless of manufacturer). When that happens I will buy a new 52V battery pack for my ebike, and the old pack can be used for the mower until it is completely dead. At a well-worn 14-Ah, my old ebike pack will still be almost twice the capacity of the stock 7.5-Ah EGO pack when that one was new.
Here is a teardown video of the Echo and EGO battery packs to show the insides:
Here’s another wrinkle. In a power outage, how many batteries do you have that can keep your smart-phone, re-chargable flashlight, and laptop computer charged for as long as possible? I have a small DC/DC converter that takes the 52V and produces 12V for my ebikes lights and radio. That 12V socket can also keep my phone, 18650-cell flashlight, and laptop charged up for a very long time, by using my 52V ebike batteries…and…my EGO lawn mower batteries!
One last note, the large 7.5-Ah pack will not only run the mower for which it is designed, it will also run the string-trimmer, which of course would make the trimmer a little tail-heavy. The smaller 4.0-Ah pack WILL NOT run the larger mower, and there is some voodoo involved by EGO to prevent you trying that. Both chargers will charge either pack, but…only the charger for the 7.5-Ah pack has four LEDs to show the state of charge.
[side note: EGO has two sizes of mower, I purchased the larger one for an extra $50 because it has powered wheels as a RWD. The smaller mower has a base-model 5.0-Ah battery pack. The 7.5-Ah battery alone is worth the extra $50]
I charge them to 75% immediately after mowing (three LEDs out of four), and then I only charge to 100% just before mowing. If you store lithium-ion battery packs at 100% charge, they will die much sooner than necessary. Store them at 90% or less, in accordance with the information we researched, found here. Doing this can double the life of your expensive packs!
Here’s another article on the EGO 56V batteries by one of my favorite writers, Karl. It’s from a year ago in April 2016, and this article convinced me to actually buy an EGO 56V weed trimmer, instead of just reading about them.
I originally thought that the DeWalt 60V packs must be 14S (fully-charged 14S packs are 58.8V). However, a teardown video showed that they are definitely 15S. A nominal 3.6V per cell would be 3.6V X 15S = 54.0V, and fully-charged they are 4.2V X 15S = 63.0V
This is cutting it real close to popping the 63V capacitors inside the popular Bafang BBS02 and BBSHD controllers. A small geared hubmotor wouldn’t care, as long as the easily up-gradable external controller was made for that voltage range, but…why use the odd voltage that nobody else is using? After looking into why, it’s actually quite clever what DeWalt did with these (warning! If you are uncomfortable with rough language, then don’t click on this AWE-some battery teardown video link)
Every major cordless tool manufacturer on the planet has a variety of 18V tools, which use five cells in series (5S). DeWalt created a clever 20V / 60V pack with 15 cells inside.
The interface is made so that…when it is plugged into a 20V tool, the pack is automatically configured as a 5S / 3P pack…with a VERY long run-time. However, when you want to use that battery pack on a more powerful 60V tool, you just plug it in, and the tool interface will automatically configure the pack as a 15S / 1P pack. High power, but with a short run time.
I know of one builder who is using these on his BBS02 ebike, and I wrote about it back in January of 2017.
If 15S interests you, the Snapper brand “might be” a better bet. It has a 15S / 2P pack that is definitely 30 cells at 4-Ah (with no fancy 20V / 60V switching like the DeWalt). However, even at 2P, it does not have very much range, so you will have to add several of them, just like Blain’s BBS02 / DeWalt cruiser listed just above.
I couldn’t find any battery pack teardown videos for these, but it uses TWO small 2.0-Ah packs to get a decent run-time from the mower (instead of one large 60V pack). The weed trimmer only needs one of these 60V packs at a pretty small 2.0-Ah.
Black and Decker 60V
B&D is still selling 36V lead-acid mowers, so its no surprise that their new lithium mowers use an existing system (rather than invest in a risky new-to-them format)…yup, the dual small 60V packs look identical to the Greenworks packs listed above. Each brand of mower does have differences in their features, but…both of them look like they use the same battery system. There is no word on whether both of them use the same 18650 cell, or what that cell-brand and chemistry that they might be. Both use small 2.0-Ah packs…
80V / 20S Systems
I don’t recommend these for ebike experiments. Not only is the higher voltage un-necessarily more dangerous, but…if you truly want to run 20S, I feel it would be easier to adapt using two large 10S / 36V packs in series. That being said, they do exist.
20S would be a nominal 3.6V X 20S = 72.0V, and when fully-charged?…it is 4.2V X 20S = 84.0V
The Snapper brand has an “82V” series (with a respectable 4.0-Ah size) that is made in partnership with Briggs and Stratton. B&S is no stranger to electric motors, and their ETEK motor is an ebike hot-rodders favorite…found in floor scrubbers and lawn mowers.
The Greenworks brand has an 80V mower, and the larger 4.0-Ah pack looks identical to the Snapper packs listed above. They also have a smaller mower that uses two 80V / 2.0-Ah packs, instead of one large pack.
This is the house-brand for Lowes, and the only size pack I can find is the 80V / 2.0-Ah
Making Mounting Adapters
No matter what size and type of cordless pack you decide you want to use, you will have to make mounting adapters for each pack. In the video tutorial above (for Blairs DeWalt Cruiser), he cut the bottoms off of six DeWalt worklights, since they were the least expensive DeWalt tool that had the slide-in interface for the batteries. Some builders have the tools and skills to make mounting adapters from scratch, but I believe most cordless battery ebike users will have to allocate some of their budget to buy a cheap tool to sacrifice (or buy a used tool at a pawn shop, or from ebay?).
Also, save the lights you cut off, they can still be used! three of the 20V lights “in series” can use the 60V battery pack voltage directly without a converter.
Cordless tool manufacturers want contractors to use more cordless electric tools, but its been a slow climb for them. I may only spend 30 minutes mowing and trimming my lawn and bushes, but…someone who does that for a living will go from lawn to lawn all day long. The only way I could see me using cordless electric lawn tools for a business is if I used the cordless electrics early in the day, in a neighborhood where the gassers are too noisy to use before 8:00-ish. After 8:00? I’d switch back to gasoline.
That being said, they are making an effort to provide larger batteries for more run-time, and one logical product to offer is a back-pack battery. I could only find three brands right now. Greenworks, Husqvarna, and Stihl. They are expensive per watt-hour, compared to clustering several smaller tool packs like the units shown above. The ads show them being used with cordless electric chainsaws, and various other tools. If you can swallow the price on these, they would make the chainsaw lighter when you are crawling around the branches of a tree when you are 20-feet above the ground…
I doubt the Greenworks backpack is selling well, since it is 82V and only 12.5-Ah. There is only so much room for cells in a pack of a given size, so the more volts you want, the fewer amp-hours you will get. Their GL900 is listed as $900
Husky makes a couple of sizes of backpacks in 36V. The BLi520X is 14.4-Ah and retails at $600…and the BLi940X is 26.1-Ah and $950.
These two guys (Husky and Stihl) seem to constantly compete with each other, so of course Stihl also has 36V backpacks. The AR900 is 24-Ah, and costs $850, and the AR3000 is the largest one at 31-Ah, selling for $900.
There is one huge issue with combining several small battery packs onto one ebike. You can attach two packs together in series without immediate damage (as long as it’s done right). In other words…an 18V pack attached to a 36V pack IN SERIES will make a 54V pack. Sounds odd, but it works.
However, if you are running two or three packs IN PARALLEL (in order to have a longer range without needing to occasionally swap from one pack to another), you absolutely MUST charge and discharge them all at the same time, and when you insert them into the mounting harness…if one of them has a lower voltage than the others? all the packs will rapidly equalize. This means a LOT of heat, possibly damage to one of them, but whats worse? It can cause a fire. This is no joke.
If you have two mounted packs (or more) and you install a switch to move your ebike power from one pack to the other (instead of physically pulling one pack out of a mounting slot and sliding a second pack into it), make sure that the type of switch you use has a neutral center position where nothing is powered.
Stick with a large global retailer of well-known “heavy-duty contractor-grade” tool batteries, like Bosch, EGO, Milwaukee, DeWalt, Makita, etc. Use a voltage that fits right in with a common ebike controller voltages, like 36V or 52V. Do NOT alter the batteries themselves, so technically you might be able to use the factory warranty if you get a defective unit. The on-board BMS’s and temperature sensors will not allow you to draw more amps than they can safely provide, so they should last a very long time…even on an ebike.
Fan-cooling the interior of the packs is a HUGE benefit, so I would encourage anyone to make every effort to find a way to get the 56V EGO or 36V Bosch packs work for your application.
Written by Ron/spinningmagnets, May 2017