When you need to control LOTS of DC current, and don't want any noise (electrical or audible), you need a Solid-State Relay!
Traditional relays actually have physical little contacts that when powered by a little signal, bang together to pass much larger currents. They have little resistance, are generally reliable, but they are noisy and they don't last as long as solid-state components. That's where the Solid State Relay (SSR) comes into play.
The SSR uses optocoupling to isolate the input signal from the power electronics. It actually uses internal LEDs and LED sensors to detect when a signal is present, so they are very safe, with practically no chance of power switched on the load side jumping to the input side.
Note: Unlike the Crydom SSR that we carry, which uses a DC signal to switch an AC load, this SSR uses a DC signal to switch a DC load.