Diode downstream of alternator?

[CovKid]

As I said earlier, a 5-pin relay. Why complicate what is a relatively simple solution.

[ghost123uk]

As I said earlier, a 5-pin relay. Why complicate what is a relatively simple solution.

[paulo999]

if you go the voltage sensing relay way, when you buy one, buy two..(if you have a spare you will never need it kind of thinking)... if they fail while you are "offgrid" they may well connect everything you dont want connected !!! i personally dont trust them. ( Just my experience)

Thanks Mocki - sounds like good advice.

[paulo999]

As I said earlier, a 5-pin relay. Why complicate what is a relatively simple solution.

Semiconductors would have been my preference vs. a mechanical solution, but doesn't look like there's a way of doing it without voltage drop* so relay it is.

* It can be reduced by doing it with MOSFET rather than diodes, but the numbers I've seen for this aren't very impressive.

[CovKid]

So do I where prudent, but you're dealing with larger current here (potentially) and its only a switch at heart. Semiconductors can be used to good effect around a vehicle (particularly with lighting), but in this instance I think you'd be over-egging the pudding. Get a good quality relay and you should have no problems with it.