Protecting a cut out relay

Hi Guys,

I need to protect a solid state relay that I'm using as a cut out relay.
The relay is activated by an Arduino and passes charging current to a battery bank. I just cooked a relay as I wasn't concentrating and forgot that without the generator running it would draw current and act as a motor..

I'm looking for any suggestions/guidance on what diode (or alternative) would be suitable.
It's working parameters are up to 36v dc and charging current of 20a (25 to be safe). Ideally the...

Protecting a cut out relay