Experiences with 36V tool battery as drive battery

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SuperHans

1 mW
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Mar 10, 2025
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Berlin
Hello,

I'm currently developing non-profit mobility aids for children with limited mobility. I'm currently using a super-light AKM-75SX and limiting it to a legal 6 km/h using a push assist or voltage divider. I want the whole thing to be truly usable, so I'm looking for a 36V battery setup that can be easily removed from the bike for charging. Currently, the motor draws about 0.5-1.0 A maximum and isn't used continuously.

I'm currently using 5Ah batteries and, for simplicity's sake, am thinking about trying 36V tool batteries, which I connect to the controller using adapters available on AliXpress. Has anyone done this before? Is there anything wrong with it? I can get by with a minimum of about 3Ah - the simplicity/usability of charging is more important! What do you think? Good idea or do you guys maybe have any other ideas?

I'd love to hear from you.

Thanks and best regards, Hannes
 
Careful some tools have the BMS in the battery. Some tools have the BMS in the tool. Here in 2012 you can read what happened when I connected a Makita battery to a radio.

"PROBLEM Makita battery drains too low and turns to trash. Won't charge any more. Yellow death light on charger."

endless-sphere.com

Makita Battery powered Boom Box

Cut the bottom off Makita BML185 18V LXT Flashlight. Got a Altec Lansing iMT800 Boom Box. Want to power this with 18V Makita power tool batteries. Boom box is normally powered with this power supply or 8, D cell batteries. PROBLEM Makita battery drains too low and turns to trash. Won't...
endless-sphere.com endless-sphere.com
 
Tool batteries could work ok but the chargers are bulky and some of them do require communication with the tool to allow them to discharge.

have you considered using recovered scooter batteries. Seems easier to stick with something that is already setup for e-mobility. These are cheap.

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Hi, amazing - that's the kind of ideas I was hoping for. Will doublecheck the BMS situatiuon and look a bit more into scooter batteries. My intention for working with tool batteries was to benefit from the countless reverse engineered adapters etc. that are on thingiverse etc. and to use these as a starting point to design a easy to use battery case/holder. Will check whether there are similar adapter for scooter batteries around... Thanks again, Hannes
 
If all you need is 4AH-5AH, you can probably find a proprietary tool battery with a self standing BMS that meets your needs. I would think that a major manufacturer's tool battery is appliance level safe. You'll have to do some research with the guys that like to re-cell them.

I have bought some used scooter batteries though, and they were better made than any ebike battery I've owned, Always inside an extruded aluminum case, BMS circuit board soldered directly to the battery tabs, No rats nest of balance wires, often present in bike batteries. Spotwelded by machine, no hand welds. Multiple thermal sensors. In most cases, the BMS needed electrical handshakes with a scooter controller and had to be replaced. All were long and unwieldy for mounting on an ebike,, being 30 to 40 cells in a 10S configuration, I initially cut some in half and folded to fit on a rack, In the end, I took them all apart for the cells.

I do own a 36V2.5AH Ryobi battery. It powered my 500W ebike. 90WH gave about 9 miles. I was so encouraged, I bought their 5AH model. 180WH only gave 10 miles. The cells in it must have had a low C rate and couldn't handle an ebike. This was 2016. They are surely better in 2025.
 
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I think the issue is that, power tool plus power tool pack is appliance level safe. Power tool pack alone may be missing the BMS circuitry that makes the pack safe since some manufacturers put that part on the tool and charger sides, not in the battery packs.

So all of them can be appliance level safe when used with their matching tool and charger, but not all of them can be appliance level safe when only the pack is used separately from the intended tool.

I power my kid's power wheel car off of Milwaukee M12 tool batteries ever since the lead acid battery it came with died, but there's no BMS in them. To make it safe I had to add a part to provide the under voltage protection that Milwaukee puts in their tools:
 
Thanks again! I just ordered a fake B&D that's advertised as having under-voltage protection, etc. So there is a chance that BMS circuitry is build in... I will check and let you guys know. All things battery related is somewhat knew to me, so many thanks for pointing me to the things to look at. I'm printing this one: Black and Decker 40v Battery Adapter by WackyEngineering right now and hope for the battery to arrive soon. If it's fitting and holding well and the battery performs and has BMS I will design an battery/controller unit with an easy to detach battery based on that design : ) I hope for a small form factor and very usable unit... Thanks again, Hannes
 
What goes wrong with lithium batteries is unlike humans they will work till exhausted. Voltage goes down till they are dead. Dead as in will not charge.

I am looking for some humans who will dig with a shovel for 20 hours or so. I am not cruel. Will give them water, food and cigarettes when their energy level goes down.
SuperHans said:
fake B&D
Click to expand...
Charge is a place where you would make a fire. That be outside.
 
Yeah, quality brand name cells like Samsung have safety vents in the cells to let the boiling electrolyte out when something goes wrong. Cheap fakes are just like cluster bombs.
 
Interesting, but this is mainly while charging, right? It's a first test only. If this goes to a larger number of people I'll dive deeper into the mystery of cells and make sure to work with safe cells...
 
It's happened to me when just prying cells apart to salvage them from packs too. So mechanical damage can cause temperature to rise to the point where they pop. Also if you do regenerative braking or you have multiple packs involved and one ends up feeding the other. Maybe a short without a fuse could get the heat up enough too.
 
If the purpose of using a tool battery is safety, then avoid counterfeit or fake batteries. Stay with major brands.

If you join some tool forums/reddits and talk to re-cellers, they should know what is going on.
 
SuperHans said:
Thanks again! I just ordered a fake B&D that's advertised as having under-voltage protection, etc. So there is a chance that BMS circuitry is build in... I will check and let you guys know. All things battery related is somewhat knew to me, so many thanks for pointing me to the things to look at. I'm printing this one: Black and Decker 40v Battery Adapter by WackyEngineering right now and hope for the battery to arrive soon. If it's fitting and holding well and the battery performs and has BMS I will design an battery/controller unit with an easy to detach battery based on that design : ) I hope for a small form factor and very usable unit... Thanks again, Hannes
Click to expand...
I've been using Ryobi "40 V" yard tool batteries in E-bikes for a few years now.

If you buy "genuine OEM Ryobi", they have a rugged and sophisticated BMS in each battery pack. Output limit is 18-24 A dependent on the size and type. These are about as safe a lithium battery as you can get.

There are much cheaper knockoffs that I wouldn't trust.

The chargers are also cheap, rugged, light and compact.

Robotics clubs use these packs, there are several pre-wired docks available. 3d printed, so I reinforce them for e-bike use, but you may not need to for your use.

Read up on how to "re-awaken" a pack that has shut itself down for safety.

I wouldn't go Aliexpress for the docks, Ebay has several people selling them, I've been happiest with the ones from Collections (Terrafirma)
 
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Thanks for the insights - that makes sense and Ryobi sounds great. Guess I switch over to Ryobi then. Will check when back from holidays. Many thanks to all of you. What a great forum : )
 
Everyone's tinkered around and done it, A pair of 18V drill packs in series is probably quite safe,

forums.electricbikereview.com

Ebike conversion powered by Ryobi

I am in the process of building a custom 10 amp hour battery for my wife's ebike conversion. Until then I thought I'd slap a couple of 18 volt Ryobi batteries in series take her for a spin. The parts consist of a Ryobi battery wall hanger and a Ryobi battery clip, both on eBay from...
forums.electricbikereview.com forums.electricbikereview.com
 
Since you also mention possibly using a voltage divider to reduce the speed,…
….One minor question.. why 36/40 volt system ?… motor spec ?
The low speed and power levels you quote ( 1.0 amp max, non continuous ), are very low and could easily be supplied using a much more common, cheaper , lighter, compact, 18/20 volt tool pack system.
i suspect the motor could be adapted to use such a system.
But you may have good reason to stick with 36 v ?
 
Last edited:
Hillhater said:
One minor question.. why 36/40 volt system ?… motor spec ?
The low speed and power levels you quote ( 1.0 amp max, non continuous ), are very low and could easily be supplied using a much more common, cheaper , lighter, compact, 18/20 volt tool pack system.
i suspect the motor could be adapted to use such a system.
But you may have good reason to stick with 36 v ?
Click to expand...
RPM per volt maybe? That's usually the reason to commit to one voltage or another.
 
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