I will doing something similar with the BLUE SEA SIACR 7650 Series SMART relay. This unit monitors my Truck ALternator charging system and when it senses the Truck ALternator is in charge mode it switches in the remote connected batteries. This switch mode is adjustable to different DC Charging voltages depending on what your truck systems uses. The idea here is only when your truck start battery is being charged the remote batteries are being charged. This prohibits the remote batteries from draining down your truck start battery.
This used to be done with large current DIODE but these days the large voltage drop (.6VDC) across the DIODES messes with the boost and normal charging modes which is normally only around .8VDC difference coming from the alternators so direct connected solenoid relays must be used now. These smart relays switches in and out when required to be used.
This is going to be my concept for having two 150AH 12VDC batteries in the bed of my truck to run a bunch of two-way radio setups and also support my camping requirements when connected to the my OFF-ROAD POPUP camper trailer which also has two each 150AH 12VDC batteries.. When being used for the two-way radio ops these batteries will be charged by the truck alternator- when connected to the OFF-ROAD POPUP the on-board converter/charger will keep the batteries charged up.
This is also the way I can spread around the weight of the extra batteries which would be a total of 328LBs for the batteries if all were mounted in the same location...
Always working on some mods...
Food for thought...
Roy Ken
