As you’ve noticed, getting bespoke batteries here in South Africa can prove to be quite a challenge. I decided to experiment in powering my VESC and my Brushless motor off a Makita 18V Lithium ion tool battery that I had lying around (exact model and price here). I thought this was not going to work due to some form of protection circuit in the battery only allowing it to be used with official Makita tools. Also, modern day power tool manufacturers all advertise their own battery technologies aimed at improving battery life and performance by having the tool “talk” back to the battery etc. That might be the case, but after sticking a DVM on the battery when it was fully charged and seeing it reads 20V, I was encouraged to at least try.
Did it work? The short answer is, under testing circumstances, yes it worked. This does not mean that this is by any means a good solution at all. At least it proves to be a feasible solution.
There are many potential problems, here’s a few:
- This battery was not designed for this purpose. Well, “duh” you might say, but there are a few more things to consider. Exact safe continuous discharge rate is not accurately known for this battery and poses problems with what settings you feed into the VESC. Getting this wrong could seriously, and permanently damage your battery. Peak and continuous max discharge rate for use with an electric skateboard as compared to a high-end industrial cordless drill will vary considerably. Usage also differs significantly: While one can use a cordless power tool continuously for maybe 5 minutes max at a time, with brief off time and repeating the process for several hours on end – this differs significantly from use with a small EV where one could typically run on various speeds, but continually for up to 90 minutes. Of course, there are many other reasons too.
- Safety. One would need to find a safe way to connect wires to the battery terminals without causing any type of hot connection or having the risk of them coming loose during operation causing serious injury.
- Mounting. Without a 3D printer or shop full of metal working tools, it is no easy task to find a safe and reliable way of mounting this to the board. A possible solution to this problem would be to use a commercially available battery mount. This is a great one I found on ebay:
- Size. These batteries are quite bulky (at least height wise). Height is the biggest limiting factor, as most electric skateboard do not have huge amounts of clearance. Some of these batteries come in a slim form factor, however they have much smaller capacities – so this option won’t work.
- Cost. This is almost certainly a much more expensive option considering capacity and less than ideal performance for this application.
A quote from a user on the enertion forums regarding use of cordless tool batteries:
“I also believe that allot of Lithium power tool batteries are just made up of 18650 cells (like a space cell) but you would probably ruin it by using them cause drills don’t pull 60A+“
The key here is that not all 18650 are made equal. Just have a look at a video from one of my favourite YouTubers to understand why:
However, this option possibly has some benefits:
- Cool. It would be a pretty unique solution, one that I’ve not yet seen done (or at least very uncommon).
- Convenience. These batteries charge enormously quickly ~45minutes. Chargers and batteries are readily available. 6Ah (and higher) batteries are also starting to appear on the market. You can keep a spare or two in your backpack and simply swop out the old one with a fully charged backup. They also have a built-in battery charge indicator!
- These batteries have built in protection circuits that prevent it to a certain degree from being damaged from overuse / excessive current draw and would even cut out to cool down if it becomes too hot. These are features not available in many electric skateboard batteries. However, appropriate and safe VESC settings would still be essential.
Above also illustrating the brake feature.