I’ve replaced those crummy battery isolators with solenoids. It’s a big improvement.
As mentioned, make sure to buy a continuous-duty solenoid.
Another benefit is the options it gives you. I wired a switch on mine to chose either manual both-battery-connect or auto-connect. I used an oil pressure switch to activate my auto-connect so it doesn’t connect the two unless the engine is actually running. Otherwise, if you just wire it to the ignition, if you ever accidentally leave it on you’ll drain both batteries.
Also, if your house battery is dead it puts a strain on your starting battery when you try to start the engine.
It’s easy to do, just remember the oil pressure switch switches a ground wire instead of a “+” wire.
