Split charging is the term used to describe the simultaneous charging of the vehicle starter battery and the leisure battery (or batteries) from a common charging source. On vehicles and boats this charging source is almost always the vehicle alternator which is in turn powered by the engine: but there can also be other charging sources not related to the engine such as a mains powered charger: solar or wind powered re-charging systems and portable generators. Modern split charge systems typically have a device that connects the starter and leisure batteries only when a charging source is operating: and electrically isolates them otherwise: ensuring that the use of one battery does not draw current from the other. It is important to ensure that the starter battery is isolated so the engine can always be started: but you also don't want the leisure battery to be accidentally drawn upon when starting the engine. TECHNICAL SPECIFICATIONS 500A Rated - Continuous Use Stable up to 16.5V Colour: Black