A 48v or 24v RV air conditioner can run off a few batteries for several hours.
I think it would be fine.
Or even just a simple powered fan would aid in moving the air better than a forced ventilation system.
If a normal battery were used to power the AC it would have to power it for the entire day since there would be no way to re-charge it while in operation. The system in London uses a super capacitor instead of a battery, since these can be charged very rapidly while the vehicle is passing through the station, but as a tradeoff they di-charge very quickly.