Trickle charge

GWR plans to use it on the Greenford branch in west London, making use of a fast charger at West Ealing that will charge the batteries in just three and a half minutes. This fast charger is essentially a battery installed at the lineside which is trickle-charged from the electricity grid. It can then discharge quickly into the train's batteries through charging rails and then start recharging itself while the train is running in service.