Got the charging software uploaded and it's working pretty well so far. Could use some more polish but it's operating!
Have an older Hitec battery charger that has a USB port for monitoring the data about the charge from it.. Unfortunately it uses an ancient WinXP software, so I got it running in linux and decoded the protocol it uses to talk to the software. Wrote my own in Go that dumps that into InfluxDB and graphing the data in Grafana.
Results were pretty good! Chamfer with is a bit larger than i'd like, and when I flipped it seems i'm off a small amount for center positioning, not sure why but will have to figure that bit out.
Went on a bit of a buying spree last night, ordered samples of a few different batteries online (32700 LiFePO4) to see what the resulting capacities and such would be, determines what kinda pack I'll build. Also ordered a couple controllers to see which ones might work with the custom firmware build.
Tore down the scooter. cheap controller and a plastic case for the battery pack, same as a bunch of others, just a generic wrapped pack of cells, 6Ah. Hopefully with some 32700s I can hit around 20Ah, and can fabricate a new box to hold them and a newer controller. Maybe even mount the controller in the box directly for better heatsinking.