Redarc SBI12 isolators - dual sense ?

[maulbeagle Senior Member Find all posts View Profile Close maulbeagle]

Hi all,

I'm hoping someone can say they've come across the same thing as me, that I'm not just crazy or installing these things wrong.
I've installed and used 3 separate SBI12 isolators in my cars over the last few years. I've come to the conclusion that they all dual-sense, even the ones that aren't supposed to.
They all work as they should by connecting the batteries when the main battery is at a high enough level, and isolating when the voltage drops on the main battery.
HOWEVER, if I wait until the batteries are isolated after driving the vehicle, then put a charger on to the aux battery, eventually the isolator will join the batteries.
So my thoughts are that the isolator is dual-sensing, or that the voltage in the main battery is somehow rising to the cutoff level.

Any thoughts/ideas ?

Thanks !

[JimmyC Advanced Member Find all posts View Profile Close JimmyC]

The sbi12 will connect the batteries at 13.2V regardless of which battery the 13.2 comes from.

[Guest Close Guest]

The sbi12 will connect the batteries at 13.2V regardless of which battery the 13.2 comes from.

I thought the SBI12D does this but didn't think that the SBI12 could.

[maulbeagle Senior Member Find all posts View Profile Close maulbeagle]

Yeah Redarc charge about $100 more for the dual-sensing model which is designed to do this. I wouldn't think the cheaper ones should do it or they have a crap business model !

[Guest Close Guest]

When you say eventually, how long till it connects both batteries?

[maulbeagle Senior Member Find all posts View Profile Close maulbeagle]

not sure, I'd have to do some more accurate testing and measurement.

[Guest Close Guest]

It is very interesting. As long as it is connecting as the battery is getting charged and not vice versa. That would be bad when it flattens the starter battery unknowingly. Perhaps your unit is faulty.

I have a dual sense VSR (Enerdrive brand) so can't really help in testing to confirm your findings.

[maulbeagle Senior Member Find all posts View Profile Close maulbeagle]

nah it definitely only does it when charging.
I've left the vehicle in the sun for a couple of (hot) days and the fridge has drained the Aux battery down to about 7 volts, but the Main is still above 12 and starts the car fine.