Just got back from a 22 mile test ride over 90 minutes. Based on the charger counter it added about 300Wh to my ride and I still had plenty of board juice left when I came back.
I have not caught fire yet.
@deckoz how retarded am I for trying this out without having a schematic for the MPPT or BMS? Hah
The TL;DR is I’m using a cheap MPPT solar charge controller + a battery in my backpack as a DC to DC CC/CV charger for a really lazy and simple mobile charger. So far it seems to work fine to charge-n-ride.