VSR (voltage sensing relay) split-charge relays.
The VSR systems are especially useful if you're fitting a split charge system from scratch and / or your vehicle was registered after the mid to late 90's with a complicated engine management system we would definitely recommend using a voltage sensing split charge relay because they are easy to fit and require no connection, or interference to, the vehicle electrics. Simply wire the relay from your starter battery to your leisure battery. This also avoids any vehicle warranty issues.
Voltage sensing split charge relays and fitting kits are easy to fit as they only need wiring from the starter battery to the leisure battery/batteries. They are suitable for older and also modern vehicles with INTELLIGENT ALTERNATORS, CANBUS and MULTIPLEX wiring systems. With volt sensing/sensitive split chargers there's no need to cut wires or take feeds from other sources (i.e. the vehicle alternator). Beware of other systems on the market that may cause electrical malfunction or invalidate the warranty on modern vehicles.
To read more about split charge relay systems and what system will best suit your needs see our Battery Split Charging FAQ's.
For the very latest vans with Smart Alternators and Regenerative Braking Systems on which VSR relays will not work efficiently see DC Battery Chargers.