The BS 500 DUAL is designed for use in situations where 2 batteries are used; for example in boats, campers and caravans. The Battery separator is a microprocessor controlled heavy duty relay which automatically connects batteries in parallel, when one of them has reached a present voltage for at least 5 seconds (13,2V/26,4V) (indicating that the battery is being charged) and disconnects when the voltage decreases below oat level for at least 5 seconds (12,8V/25,6V) (indicating that one or more batteries are being discharged). The Battery Separator is an excellent alternative to a battery isolator. The main feature is that there is virtually no voltage loss, so the output voltage of alternators or battery chargers do not need to be increased. Another advantage is that the Battery Separator can be mounted without changing the existing circuit. That doesn’t just make the Battery Separator very easy to install, but it’s sometimes also the only option, because some alternators do not accept a Battery Isolator between themselves and the battery.