A badly installed split charging system can be very dangerous if the correct fuses, relays or cable size are not used. Over the years on both commercial vehicle, camper vans and some retrofit system in motorhomes, we have seen some dangerous installations which can lead to over heating cables which can catch fire.
Correct cable size and fuses in the correct place are extremely important to a safe and efficient system, especially if its a vehicle you’re planning to sleeping in. There are a number of different relay types including 12volt trigger relays, voltage sensing relays (VSR) and DC to DC chargers for smart alternators.
12 Volt Trigger Relays
These relays work well and are simple to use, they are either ON or OFF and are ideal for older vehicles that has a 12 volt trigger from the alternator. This will switch the relay on and off when the engine is running. Unlike the VSRs, these are a stand alone system and can not engage unless the engine is running.
Voltage Sensing Relay
These relays for simple to install and will work well with most vehicles. They operates when the engines alternator starts charging and the voltage rises to 13.6 volts and above. Then off when you switch the engine off and the voltage then drops. These are great for a simple install however if you have any secondary charging systems on the vehicle, these can unessaserly switch on.
Smart Alternator Battery Chargers
If you have a vehicle with a smart charging alternator, a DC to DC charger would be necessary. Smart alternates only charge the vehicles battery during certain times whilst driving. This creates less draw on the engine which gives better efficiency. This means that without a DC to DC charger you would not get a full charge to the leisure battery. Think of a DC to DC charger as a self switching 14.4v battery charger that’s 12v, just like a garage mains 240v battery charger but 12 volt. These can come in different charging variations from 4 amps to 60 amps and above.