I used 21700 p42 lithium ion cells for one battery (they’re out), and a123 26650s for the other battery also from bh, and they’re out of those specific full capacity cells. I can’t find 100% capacity a123s anymore and only at 90% available anywhere. If u have the room they’re really cheap these days at like 30cents a cell
I currently have a 14t front and 39t rear. which gives me a 1:2.079 ratio, and then the gearbox adds another 1:2.35 reduction. So if my numbers are right and if the rated 3800 RPM is for the motor and not the output shaft that would put the top speed of the bike at 33mph. But they say you can hit 6000rpm with field weakening, which would put the top speed around 52mph.
I don’t know many dirt bikes but I recently was close to the qs138 90 with I think a 13t and 520 chain and sounded awful. I really like the 17t and quiet.
I mean the gears in the motor.
Those are all tiny sprockets. Id rather go bigger in the rear so can be more efficient, and much quieter, and I imagine the chain will last longer and you could probably use a lighter thinner chain like the 420
I don't think the qs138 90h has a great reduction, that motor is just 1:1. I intentionally went with the 70h for the gear reduction because everyone I've seen uses the 90h had a giant sprocket on the rear nearly the size of the wheel. Sp o was hoping to avoid doing that.
I think the 70 and 90 tell the stator height. The magnets and also likely 20mm longer and same number. 29% more motor. 29% more torque.
That's awesome that you made them by hand. I'm just starting to learn about all of this, the only experience I have with this stuff is building RC cars years ago lol. It all seems to be the same principle just bigger everything and far more functionality.
Yeah, I was gonna use the plastic holders they come with, and build a new metal box simular to what they're in now.
Here's a pic the completed battery (minus the BMS) that I built using the SPIM08HP cells. I'm looking for a shifter cart frame to use these in for my next project. I also considered building them to sell. Just not sure if there will be much interest due to the size. They definitely wouldn't be a good choice for a bike build. This battery is only 20s 2p (72v 16ah). I think I'm going to double it for a 32ah when I build the cart build.
Yeah, I can't wait to try them out. They have excellent discharge and charging rates. The plastic cell holders leave a small air gap between each cell, making cooling very easy. You could even add a fan to blow through the side of the pack if needed. I was going to wrap each pack with heat shrink before bolting the end plates on to add some water resistance which would probably increase the operating temp some. Any idea how much something like this would sell for? I couldn't find much for comparison online.
