Yah we haven't discussed charging, or even how a bms interfaces with a charger (or a controller)
Here is a good video about charging manually as well. Eventually you want to get everything down to the cell level and automatic, but you can at least get rolling cost effectively, and 18 cells is more manageable manually than others
EVTV Motor Verks | Electric Car Conversion Videos
The leaf cells are a bit trickier than the lifepo4 cells fyi, they might not be as resistant to overcharging, and the special voltages of the leaf cell are limiting your cost-effective bms and charger options, so you might want to consider lifepo4 too.