redarc

These latest Redarc smart solenoids have an annoying problem due to the cut out voltage being set at 12.7 volts. This means that the solenoid stays energised for hours after switching the engine off until the starting battery drops to 12.7 volts. This means you fridge or whatever is draining both your batteries rather than just the auxiliary. There is also the 0.8 amp drain of the Redarc's solenoid coil wasting your precious battery power for no good reason.
In practise, mine stays on until 12.49 volts was measured at the main battery terminal on the Redarc and after contacting them, they say there is a + or - 0.25 volt tolerance to the cut-out voltage.
I will be adding a relay that disconnects the black earth wire coming from the Redarc coil when ever the ignition is off so that my starting battery isn't discharged for hours unnecessarily...

I also experienced this with other brands (use only Redarc now) and just mounted a panel switch to switch earth. It also has a smal led in the switch that illuminates when the solenoid is on. Just flick it off and on after shut down and it's ready to go from next start-up. Needless to say there is no lost power!!

"These latest Redarc smart solenoids have an annoying problem due to the cut out voltage being set at 12.7 volts. This means that the solenoid stays energised for hours after switching the engine off until the starting battery drops to 12.7 volts. This means you fridge or whatever is draining both your batteries rather than just the auxiliary. There is also the 0.8 amp drain of the Redarc's solenoid coil wasting your precious battery power for no good reason."

Not quite correct.
The very latest ( march 09 ) mkIII has a 12.7V drop out ( previous model had a 12.5V drop out ) and the solenoid driver has been given some smarts and the current drain drops from ~0.5A when activated after a couple of seconds to ~0.18A.

I've just changed out my previous redarc with the very latest and it is a significant improvement over the previous model. The solenoid is identical but the electronics has been upgraded.

I've confirmed the operation with bench testing prior to installation in my vehicle.