Speeduino

Billzilla wrote: ↑Fri Jul 20, 2018 11:38 pm Thanks. It was suggested elsewhere that I should just use a plain solid-state relay. Does that sound feasible?

A solid state relay meant for AC will generally not work on DC, the output triac or thyristor when switched on will stay on. They need the zero crossing on the supply being switched in order to turn off.
You need a relay that is meant for DC to ensure correct operation

That one is a DC SSR, not AC.

Hella also makes an appropriate DC SSR , if your load isn't too many amps

https://www.amazon.com/HELLA-H41773001- ... B000VU5FPE

Thanks - That could be a good thing as well.