How are they being done? A two car pair, presumably, but is it model power car and trailer, or two power cars?
One story went that the compressed air system originally powered the toilet feed, and if the toilet was flushed, you lost the brakes, but that must have been an exaggeration. We had a prototype in, but nobody said it was a double battery layout, with the engine start having its own system (it beats the cleaners leaving the lights on overnight) Soo… the charger went on the obvious socket on the one side, like all the other sets we had, and when the nobs turned up next day for a demo run, they couldn’t start the engines.