Trough battery spaces between the plates (the troughs) were filled with dilute sulfuric acid. So long as the box was not knocked about, there was no risk of electrolyte spillage. Trough battery The trough battery was a variant of Alessandro Volta's Voltaic Pile and was invented by William Cruickshank c. 1800. Volta's battery consisted of brine-soaked pieces of cloth sandwiched between zinc and copper discs, piled in a stack. This resulted in electrolyte leakage as the weight of the discs squeezed the electrolyte out of the cloth. Cruickshank solved this problem by laying the battery on its side in a rectangular box.
NZR RM class (Edison battery-electric) looked like a passenger carriage, but each end resembled the front of a tram from that era. The body was built by Boon & Stevens, the noted tram-car builders of Christchurch, in 1926, and equipped with Edison battery-electric equipment. Capable of carrying about 70 passengers, with 60 seated, and a separate smoking compartment, the railcar had a range of about on one battery (charge). Apparently, a layover of about 4 hours was needed to recharge the battery. When introduced the railcar was billed as capable of being used on the Christchurch-Little River and Christchurch-Rangiora runs as well as being available