Dump load controller kit
 

Found this kit at Hurd Solar | Dump Controllers

un-assembled Controller Kits - $14.50 each (plus S&H of $3)



http://www.ghurd.info/images/DC/DumpController2.jpg

http://www.ghurd.info/images/untitled.gif

Instead of using a power FET (IRFZ44N), It looks like you could skip using
LED2 and take those LED wires right to the control inputs of a Solid State Relay (SSR).

The SSR could be used to connect a load to an inverter, or provide AC power
to any device you choose.

Looks like a neat little package.. The website explains how to tweak the hysteresis a bit.