The duplicate secondary batteries each consist of twenty-five 72 amp-hour traction cells, manufactured by DP Battery Co. The largest item of charging equipment which is accomodated in the vehicle is the petrol engine charging set. This is a standard unit supplied by Petters of Yeovil for all small automatic exchanges. It consists of a 2hp water-cooled single cylinder petrol engine directly coupled to a 500Watt DC generator. It is mounted centrally on the floor at the front end, on rubber anti-vibration washers, and a galvanised steel tray with drainage for the collection of surplus oil and water. The engine is cooled via a radiator (not by tank cooling, as would be normal), as this saves space and weight. A pulley at the front end of the engine is attached to a fan (via a whittle belt) associated with the radiator, which is mounted above the engine. Access to the radiator, fan and belt is from a door in the front wall of the body this also being the means of entry for the engine during installation or replacement. The radiator fan draws air through the front end of the body, pushes it through the radiator and expels the warm air through a duct, which terminates at louvers high up on the end wall, preventing hot air entering the main body.
As per normal, the engine runs unattended, until automatic trip comes into operation when the battery is fully charged. This could lead to the engine overheating, and to prevent the radiator being short of water there is a store tank under the floor, which is connected to the gutters by 1” pipe. This water can be pumped into the radiator by a semi-rotary pump, until water is seen to flow from the overflow pipe onto the tray underneath the engine. Instructions being that the pump should be used before each charge. The storage tank has a water gauge, and overflow vent, and an external filler, so it can be filled from a bucket as required. A two gallon petrol tank is built into the floor under the brakeman’s seat. This has a gauge and external filler.
There is also a Tungar rectifier for use when an AC supply mains is available. The batteries are worked on the charge-discharge method regardless of the charging method. The rear wall of the brakeman’s cabin (above the tool locker) has two wooden panels. The top being for the fitting of the supply companies fuses and meters, the lower for the main switches and fuses for the Tungar rectifier and lights.