This is a wiring diagram to set up an emergency 12 volt Bilge pump during power outages using a battery that is been trickle charge by a solar panel. I am using a 12 volt wall plug transformer that I had laying around, it connects to the coil relay to turn it on,when the relay is on, the battery is connected from 87 to 30, when the power outage happens the coil looses power and then 87a connects to 30 and the Pump comes on. When the power comes back then 87 connects to 30 again and the Bilge pump shuts off.
I am using a 12 volt Solar panel to trickle charge my battery through a solar charge controller, Some people don't use the charge controller but I do for the reason been that the charge controller will prevent the battery from overcharging.
I am using a 5 pin automotive bosh relay, I bought them locally for about $5.00 each but I have seem them online as low as $2.00 each: http://www.parts-express.com/12-vdc-aut ... e--330-073