For this project, I selected a solid-state relay optimized for DC.
The pump needed to run off an existing 48V battery bank, and available SSR's inputs would not permit a voltage that high.
It requires a 4-32Volts
Also, common 3-Term regulators like a 7812 can't take that high of voltage either
I made a simple DC voltage regulator with a BJT & Zener Diode
I built the controller in a J-Box so conduit could be run from the DC power distro box.
I mounted the relay on an aluminum strip for heat dissipation.
I included options for different types of switches to call for pump. A NO or NC switch can be used.
I made it as self-explanatory as possible to make it easy for the installer to connect.
Top Center: Here you can see my 15V linear regulator for SSR signal input.
Bottom Left: the SSR input side
Bottom Center: the freewheeling diode (TO-220 device) to clamp the spike when the pump turns off due to the inductance in the pump's windings. Also, there can be spikes just from the DC brush-type pump running. This should reduce the stress on the SSR's output section.
The power switch side of the SSR.
Connecting this controller to a 48V battery bank should normally never go above 60V. Even in many possible fault conditions within the 48V system, you still will remain well below 100V
For heavy loads, ie up to 60A, the channel resistance of the MOSFET on the output section of this SSR will suffer I2R that will generate heat.
The white silicone heat-sink grease is h