Charging relays are suitable for charging 12v trailer electrics and will charge a caravan leisure battery and/or power the fridge, while the vehicle is running. It also protects the vehicle battery from drain when the engine is turned off.Combination trailer relay with automatic voltage monitoring and switches the power supply from car to trailer/caravanSelf switching voltage sensor relayProvides power to charge auxiliary battery (power fridge on a caravan)Automatic monitoring of voltage and current availability from car’s alternator/batteryNo separate signal wire necessaryAble to switch 30 amp continuously when available from car’s alternator/batteryAdjustable factory set voltage trip with narrow band hysteresisOver temperature protectionLine voltage drop compensationLow voltage drop (around 0.1v) at rated outputMade in the UK
