This is coming together. Time to start documenting it.
First, I needed a cell discharger to test the capacity of my scavenged cells.
Then, I needed a way to weld them together to build the pack.
After charging all the cells in my BMS initially, I realized I would need to do so a second time to get good capacity numbers. That prompted building a 10 cell charger.
I've already worked out the drivetrain by cannibalizing two Razor scooters I got off Craigslist for $24. The scooter rear wheels were 'turned' to free the sprocket mounting hub from the wheel, a groove cut in my mountain board wheels, and the two were joined x2. The entire process was captured on video, but needs a lot of editing..
Instead of hanging the pack below or mounting it on top of the existing board, I want to inlay the 10s5p battery pack. I would like the cells to live within the thickness of the board more/less, but 50 cells requires a good deal of the board to be removed to do so. So far I'm leaning towards routing out linear channels the diameter of the cells from end to end. I would need to make the board about 4mm thicker to accommodate the cells, which I plan to do via gluing on two strips of luan plywood. The board is curved though, in two directions, and both ends kick up at a 20 degree angle so all of this is going to be a little complicated.
For the hand control I've decided to adapt an aftermarket Wii Nunchuck. They have an I2C interface, which I already have talking to a 3.3v Arduino Pro Mini. Using the 3.3v version allows me to directly power the NRF24L01 module I intend to use to talk to the board. The plan for the control protocol is to just send everything the Wii Nunchuck produces, with a prefix (to key the board to the controller). I may scale down the accelerometer data if it proves to be too much. There was originally going to be a small OLED display in the remote (it is clear/blue), but I think I destroyed it trying to desolder the pin headers it came with. Two of the traces lifted and I haven't gotten it working again yet.
The board electronics also have a couple pending points of contention. I have 6 appropriately rated logic level power mosfets slated for this project, but I had another thought. The BMS I purchased for the battery pack I'm building has 5 hefty power mosfets onboard for over-current/under voltage cutout. They are not logic level, but do have two 'competing' onboard BJT transistors driving them. As in... the outputs are tied together... directly to the gates. I don't get that bit, but I do have two good spots now to inject some signals and see what happens. I would ultimately lose the ability to independently control the drive motors if I did this (power steering of sorts), and I would still need to implement braking mosfets outside this package. Since I do have the spare mosfets to do everything externally anyway, without messing with the BMS, I'm torn right now.
That is about it. Lots of video, waiting to be processed... Stay tuned.