The Isolators are diode based, and the diode reduces voltage by ~0.4 to 0.7v, which slows charging of house batteries significantly basically ensuring a premature demise when van dwelling.
Some of these isolators have some wiring to influence the voltage regulator, tricking the alternator to produce more to overcome the loss of the Diode.
The heatsinks are required to cool the Diodes, and are basically wasting energy as heat, turning engine HP into heat.
The Continuous Duty Solenoid is a much better option, but like brake pads they wear out, and do so faster the harder they are used. Harder meaning passing more amps and the more cycles it goes through and the higher amps it is passing when contacts close or open.
The CD solenoid is a HeavyDuty relay and sometimes is also called a contactor, but the word 'contactor' is generally used more in AC wiring than DC.
The BEst CD relays/solenoids have silver alloy plated contacts. The two smaller studs for wires are the triggers to close the contacts. Ideally, these trigger wires would close only after the engine is running. Less ideal is any ignition circuit which goes live when the key is turned to ON. One does not want house batteries contributing to starting current. this will wear the solenoid contacts faster, and possibly damage sensitive electronics hooked to house battery as the starter can cause a voltage spike when disengaged.
One can also put an illuminated switch on the solenoid trigger circuit and manually control when the alternator feeds the house batteries. This circuit can be live only with ignition or live anytime, depending on where one takes power for the trigger circuit.
I recommend one place 2 digital voltmeters on their dashboard, One for the engine battery, one for the house battery.
These voltmeters should be 3 wire voltmeters, with the third wire being a voltage sense wire and hooked directly to (+) terminal of engine or house battery.
When the Solenoid fails, usually the contacts fuse together, leaving the driver unaware that they are not isolating their engine battery with engine off, and cycling,( and damaging) the engine starting battery. If the two voltmeters always read very nearly the same one will know their solenoid has failed. When the house batteries are depleted the two voltmeters will be very different until the house batteries get into the 80% charged range. Much depends on the thickness of the wiring used.
These voltmeters are what i use, and can ( and should be) calibrated with a real digital multimeter once installed:
https://www.amazon.com/bayite-wires...d=1480454857&sr=8-1&keywords=3+wire+voltmeter
Another product which I like and use is this ammeter. One only needs to slide a wire through the round sensor to measure amperage.
https://www.amazon.com/gp/product/B01DDQM6Z4/ref=s9_dcacsd_bhz_bw_c_x_3_w
https://vanlivingforum.com/Thread-17-Hall-effect-ammeter
6v golf cart batteries have nearly the same footprint as group24 12v marine batteries, but a few inches taller, and are indeed deep cycle batteries, not a compromised marine battery.
Here is a group 24 side by side with a real deep cycle battery the gc-2 6v golf cart battery:
source and a good read:
http://www.pbase.com/mainecruising/deep_cycle_battery
