I’m tempted, but at 2500mah, I’m thinking I wouldn’t even make it 6 miles before I’d need to swap batteries. That’s roughly half the distance of the 10S2P 25R5!
I may not even be able to fit the 12 A123’s in there when I get the real thing. Would you still pick that option if it was 10S1P?
Your right, then I’d pick anything 10s.
agreed! but that is the hub motor. There is no much difference in skateboard, belt electric skateboard or hub motor electric skateboard riding on rough pavement at same speed. just curious maybe Mellow can work this out…thick rubber??
The solution is simple: more urethane. My cheap little Acton Blink Hub can ride on my bumpy road with little problem. The only difference is in like 5mm of urethane. I that if X2 made their wheels 5mm’s thicker, I’d probably be quite content.
I definitely think Mellow has solved this already. This whole endeavor has me appreciate their design more and more. Of course, certain things sound like magic. Like how can they eke out 1000 charge cycles on 20R’s when the spec sheet claims 250?
These magnets look a bit poor. Big gaps, small and most likely to come loose with a touch of heat.
It’s all about how you treat the cells. Users on this forum sporting a good BMS and carefully checking the pack every once in a while are bound to get over 1000 cycles
I’d love to hear more. Do you have any links you can point me to? I’m thinking that there are two aspects to this: (1) use a BMS with balancing, and (2) don’t use the full discharge of the battery (e.g., if you have 20A discharge, use max 10A). Any other tips?
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries I have family members who own Chevy Volts and they gauruntee a certain number of years on the battery because they don’t charge or discharge the cells fully which allows for longer life. This does shorten the range of the car each trip but I believe it’s worth it in the long run
Thanks! As my next step is batteries, this is good stuff to know. I plan to do a three way comparison of batteries that should be able to fit in the swappable pack:
With the above in mind, I’ve been having fun getting ready with spot welding.
I also acquired a bunch of volt meters, a hobby charger, a voltage alarm, and a bunch of other stuff. I’m going to take some good advice and not prototype with a BMS. It just introduces another point of failure.
It was a challenge, but it looks like I’ll be able to get 12S1P with the A123 26650 cells! Ultimately, the dowels were about 0.3mm thicker than the batteries, and I couldn’t get them to fit. So I capped each mostly-discharged battery with Kapton tape and took the direct approach. I used those soft earplugs as a sort of putty to help me get the cells at just the right height.
I think I’ll do a four-way comparison of batteries:
Taking some good advice from @Hummie, I’m going to skip the BMS for now. It just complicates things. Instead, I’ve got a Hobby Charger, temperature sensors, and a boat load of voltage LEDs coming in.
But will ur charger do a high enough voltage?
Maybe get some 6s balance plugs u can wire to the cells to use the battery monitors more easily. Maybe solder to cells directly or better just solder the wires to copper foil around magnets taped on.
That’s the plan! I’m going to spot weld two packs of 6, soldering two wire between each nickel joint. One for balancing, and another for monitoring. My hobby charger only goes up to 10S anyways, so it’s much more convenient this way. My voltage alarm also only goes up to 8S.
I received my new LG HD4 batteries, which are capable of 25A discharge. My plan was first to simply build a 10S2P setup, which would get me 50A, but then I realized I could do 8S3P by removing the BMS and going with the hobby charger approach. So I ordered 4 more batteries and waited… Then I realized that, with a little more case hacking, I could fit 30 batteries in that little enclosure! So I ordered 7 more batteries and waited…
I’ve finally got my perfect hot swappable battery. It’s capable of 75A discharge and 6300mAh @ 36V and I can simply plug it into my hobby charger to balance while charging. So I should no longer be current-limited in my builds.
First, I made some more room in the case with the dremel and cut a small square hole for the female 10pin JST-XH connection. I then glued that in, ensuring there was enough clearance for the little guiding slots on the male connector to fit.
I then ran through a dry run, just like I did with the A123 26650 batteries. Figuring just the right placement to ensure everything will fit.
Learning from last time, my approach to building the pack was do all my soldering first, then to do the spot welding. This is MUCH easier than soldering between batteries. It also looks a lot nicer.
I also labeled everything on a sharpie, so I wouldn’t have to think while welding.
And there you have it!
This is a really powerful battery for its size. I’m really happy with the results. Next steps are to weather product and heat shrink and all that, but I’m still waiting on materials. I think I’ll go back to the chassis/VESC hacks while I wait.
Now that I got the batteries good to go, I started work on the enclosure. My biggest issue was with the connectors taking too much space and the 10AWG wire not being flexible enough, so I had to do quite a bit of work on the VESC. Here’s what I did:
I tested this with two VESCs, and with the above changes both will fit fine. Right now, so I’m testing a simple single belt drive setup. I’m going to put in on my little bench “dyno” and ensure that the heat isn’t an issue or anything before I hack apart another VESC to get it to fit in there. It’s SO quiet in FOC, it’s amazing! I’ll send a video later.
I’ll clean everything up later, once I have it tested.
The main downside with the Onan X2 hack is that it doesn’t work all that well for belt drive, since the motor lacks clearance under the board. Anyone know where I can get a longer motor mount? I need it to be about 3/4" longer so that I can use this approach for my Mini Rover build.
Any updates? Great work so far!
Thanks! Unfortunately, one of my VESC-X’s from Enertion was DOA, so this build is waiting on that. However, I implemented a second Onan hack with my Rover Build.
Here’s a quick clip: https://www.youtube.com/watch?v=0fWOcp-MFo4&feature=youtu.be
Hey man, we met at the makerfaire today and I gotta say I’m super inspired by your builds. Hot swappable batteries are a great idea, and it’s pretty awesome that you were able to fit 10s3p in that tiny enclosure. I’m going to have to try to play around with the idea of a removable battery.
Also met you at the faire today. Check out my board “fishie”
