Not wanting to hijack that thread, but…
I’ve been using a Hitachi battery backpack for a bit now, and I must say it’s quite versatile and a convenient way of swapping vehicles. That’s a 10s8p, 750Wh, (50A), now with a VESC 4.12 inside. And it just takes some simple software changes to swap between electric skate, electric kite buggy, and drift trike. (and Line Trimmer…). The backpack is well designed with ample padding and straps, which makes it feel comfortable to carry, despite its 6+kgs. Using Speakon connectors for phase wires, and RJ45 for whatever else.
Those backpacks were available for super cheap last year (NZ$230), and they really do the job. Could be fitted with better cells and different BMS later on if needed. 