6.1 An engine shall be provided with either:
6.2 When the sole means of starting is by battery,
the battery shall be installed in accordance with regulation IV/21 and
be in duplicate and connected to the starter motor by means of a “change
over switch” so that either battery or both can be used for
starting the engine. In normal circumstances, the use of both batteries
in parallel should be avoided to prevent simultaneous discharge of
both batteries. Charging facilities shall be available for the batteries
when the engine is running.