DC-DC Chargers:

SolarBox offers a range of DC-DC chargers for use in dual battery systems in vehicles, caravans, camper trailers, motorhomes or boats where the alternator and the start battery are used to charge the service battery. 

Vehicle manufacturers are now introducing smart ECU (Engine Control Unit) controlled alternators to increase fuel efficiency and reduce emissions. Smart alternators deliver a variable output voltage and are shut down when they’re not needed. The DC-DC charger has an engine running detection mechanism which prevents discharging of the starter battery when the alternator does not supply power. DC-DC chargers will also protect the alternator in lithium systems where direct charging can overload the alternator due to the low impedance of the lithium battery.

Note: The isolated version has an additional input and output NEGATIVE while the non-isolated uses a common negative return. If both your start and house batteries share a common negative return (ie chassis ground) then you do not need the isolated version.