Check out the datasheets for the components in question. They are MOSFET SSRs, not triac SSRs. The SSRs, at least for the one praondevou linked to and the first one that OP linked to in post #19 are rated for DC.SSR's WILL NOT WORK for the DC portion of lordratner's application. It will turn ON, but he will have to pull the fuse or otherwise cut the DC power to the box to turn it off. I am betting that he will NOT be happy about that development.