Trailer Breakaway Kit Charger - D2902

I have a tilt deck trailer which had the emergency brakes directly connected to the big battery for the hydraulics from the factory. The wire from the battery to the e brake switch kept blowing the fuse whenever I ran the hydraulics as the pump motor also used the wire for the e brake switch supply as a current path. I installed this charger unit to primarily act as a weather tight diode to ensure current could only flow from the battery to the e brake switch. It does this perfectly. However, only 4 stars as this unit doesn't appear to charge the big battery at all when the truck is hooked up to the trailer. I have a separate DC-DC charger on board for this purpose so it doesn't matter in my application but this could be an issue for someone else who is expecting it to charge a small 12V 5AH battery like these would normally be connected to. Also, don't reverse the black and red wires. It will burn up the diode inside when you activate the e-brakes. Whoops...