I've been using a solid state relay (SDP4040D) as my primary power switch. Bu today I was adding some new stuff and checked the voltages around the system. The solid state relay was dropping 1.5 volts! I checked the specs and sure enough it can drop up to 2.5 volts at full current. This is not good when we only have 12 volts to start with. So I'm replacing it with an ordinary 100 amp relay. I don't need 100 amps, but the unit has the right terminals to just swap in.