I want to build a 20S battery and need 20 cells, so I have 72 volts and 72 Ah.
I want to buy a QS 138 engine.
You need to clarify exactly what you “want”..
Why do you “want” 200A ?
200A at from a 72v pack would be 14,000 watts !..
.......and need about 60 of those 72Ah cells ..(or...