so yeah, first time making an electric vehicle. the intent is to reuse the battery and ESC on an ebike.
A lovely person at the event i brought the motorized cooler kart to traded vehicles with me for 10 minutes, and i got to ride his electric mountain bike with a mid mount motor, and it was awesome, so i have the itch for that now.
Anyway, more of a goofy and fun project, I wouldn’t say it was practical, and definitely won’t change the world, but hopefully is brings some entertainment to your lives! :)
Nice build video! I’m also a sucker for a funny unit conversion from meters/metres to burger units. And wood- and metal-working, batteries, speed controllers, motors, micromobility, and beer? Instant subscribed.
You mentioned crimping versus soldering, and I’m poised to agree, especially in a mobile application with vibrations. Although I wanted to mention another reason for crimping: in the event of an unfused, high-current short, there may be sufficient energy from the cells to instantly vaporize the solder, causing hot spall to fly everywhere, potentially combusting flammable material. For this same reason, ham radio towers will always crimp their grounding conductors in case of a lightning strike.
Have you considered cross-posting to [email protected] ? Also, did you have a booth at Open Sauce?
oh, thats a good point on the heat issue with solder… i mean the BMS and fuse should save it, but i hadn’t thought of that. Do you have recomendations for how to attach the main bus wires coming off the battery in a non soldered way? cause with flat top 18650 based batteries, you have to spot weld nickel strips, and soldering the main wire to the strip before spot welding is the only thing i can think of. If you go with something like headway lifepo4, they are screw top, so you could fab a contact plate that the wire crimps into, then screws to the battery, but yeah - no idea how to do something like that with flat top batteries.
I’m not an expert with building battery packs, but I think solder isn’t a problem for connecting the nickel strips, so long as it’s only a fraction of the whole pack. And if it’s encased within the battery housing, spall won’t be as bad of a problem. The highest currents would be where the “strings” are aggregated together in parallel, and that’s usually when heavy gauge copper is used.
I recall that Aging Wheels has done videos on cell replacement, and I think maybe there was some sort of copper/brass busbar which aggregated the various nickel strips and then had large screw-down terminations for attaching external cables.
Rewatching your video again, do I understand that your emergency cut-off is inline with the full battery voltage? If your design had a smaller auxiliary 12v battery for powering the electronics, you could have a low-voltage control signal that closes a normally-open contactor that connects the main battery. Your emergency cut-off would be in-series of the control signal, so that loss of the signal immediately cuts off main battery voltage.
The same signal wire could be routed around to other safety sensors to isolate the main battery if something is wrong. In the most extreme case, the wire could be routed so that severe structural damage would automatically sever the wire.
This would also reduce the amount of heavy wire to only where it’s needed, with some weight savings. Air conditioner condensers do this same trick, so that the safety sensors don’t have to be rated for full 240 VAC.
yeah, the emergency kill switch had the full power going through it. I did something similar with relays on the back with the initial esp32 control, where if the relays were powered but no signal was sent to the relays, it would close the brake pins on the cheaper ESC’s as another safety feature.
it was kinda cool, a little kid (like, elementary school aged) came up and was asking about the project, with his dad right behind him. the kids questions were all pretty much around how he could potentially make something similar. I answered them in an age understandable way, but also walked through all the different potential failures and how it related to saftey, and how I added things like the relays, battery fuse, and cut off switch to mitigate the risks. basically saying “yeah, making something like this is dangerous, but you shouldn’t let that get in the way of making your ideas a reality - its just important to walk through those risks and mitigate them as best as you can, and think if you can reach an acceptable risk before you spend money and time”. The dad didn’t say anything, but i could tell he was beaming since the kid was realizing all the safety stuff, and realizing that thinking through that stuff is very important. about 1/2 way through, the kid was just asking more safety related questions haha
That’s wonderful that children are interested in the project. This and related projects would be great to showcase at Open Sauce. I certainly enjoyed this year’s displays.
yeah, i went the past 2 years. sadly driving a project down wasn’t in the cards. Both times i brought a body mounted project though. First year it was a 3d printed cat treat dispenser that would track the distance my cat runs on a cat wheel, then gives him a single treat after he runs a certain amount. I had a mini version mounted on my chest. This past year, i brought some arm mounted EDF’s that I plan on using to propel myself on skiis in the snow. I plan on making videos about both eventually, but im trying to space out larger projects like those (and the cooler kart) with smaller ones :)
Bruh sounds like your wore those breaks out. Honestly though, where I live a motorized cooler could actually be a thing people buy. It would need sand tires though.
yeah, the VESC firmware has traction control settings, so each speed controller is talking to the others and has a maximum allowed speed range between the wheels, which might help for sand? trying to accelerate on wet grass, there was a bit of slip, but you could hear the motors all micro adjusting their speed, and eventually you would get moving enough that they all went back to full power. sand might be a bit harder because the wheels + weight would want to dig into the sand.
but yeah, it was pretty nice - when i went to the general store to get ice, the people working there were unloading ice from a truck up on the street, and walking it down in plastic bins (probably a 2 or 3 minute walk from their van). They looked at the cooler kart with envy haha - so i could see some applications for it, but they are all fairly niche, and less transportation focused i suppose
Why could you not mount the axles in line with each other? It’s a cool project, and I’m not trying to hate really, but the main axle being mounted above the wheels like that just makes it look kind of goofy. Lol
well, I wanted to to be a goofy and unique project, so having the wheels be in the “normal” location would be a less interesting to me. Also, the trike had a “male” axle for a wheel to mount to, and the hoverboard wheels also had a “male” stub coming out of the motor hub, so mounting them together would have required something to offset and join the parts together. Since I wanted to do 2 wheels on each side, a triangle just kind of made sense. In retrospect, they should have been a bit shorter so the top of the cooler was level. I chose to not use cad, since i have been relying on it a lot for other projects, and sometimes its fun to just make something and kind of make it up as you go along, but if i had designed it in the computer first, then i would have realized that the rear wheel height was too high. :)
I’m not sure I was clear enough. I didn’t mean to suggest that the wheels should all be mounted on the same axle somehow, I just meant that they could be in the same plane. So, you’d still have three wheels in line with each other on each side, but all on the same level so that your trike frame sits flat.
Cool. Sorry, I’ll show myself out.
