Solar on aux only with redarc SBI12

[mjr350]

Hi guys. I have just received a 140w solar panel and i want to throw it on the roof so it's constantly changing the aux battery but I've only got an SBI12. Is there a way to hook it up so that it doesn't hold the solenoid closed. Im thinking some sort of relay that closes when the redarc is open and opens when the redarc is closed or should I just ditch it and buy a dual sensing isolator

[Winnie]

If you connect the solar to the aux battery, it won't hold the solenoid closed, it will stay open so you only charge the aux battery.
If you want to keep both batteries topped up then the dual sensing SBI12D is the better option, you can get them for $150 if you shop around.

[mjr350]

I read on here somewhere that the solenoid would hold closed if a charge was applied to the aux while the both batteries were connected and wouldn't open no matter what voltage the main drops too until the charge to the aux is removed

[Cuppa]

I read on here somewhere that the solenoid would hold closed if a charge was applied to the aux while the both batteries were connected and wouldn't open no matter what voltage the main drops too.

Depends how the solenoid is connected. Most people connect it the opposite way to which you describe to prevent the starter battery being inadvertantly flattened.If yours is not connected like that, it should be a simple matter to switch some cables around to ensure it is & then you can do as Winnie says. Every chance it is already wired to prevent starter battery being flattened though. Only reason you might want a dual sensing solenoid SBI12D is if you wanted to connect the solar to the aux battery & have it charge both aux & starter, although charging of both could be achieved by connecting the solar to the starter.

NB. ‘Closed’ = connected
‘Open’ = disconnected

[the evil twin]

Hi guys. I have just received a 140w solar panel and i want to throw it on the roof so it's constantly changing the aux battery but I've only got an SBI12. Is there a way to hook it up so that it doesn't hold the solenoid closed. Im thinking some sort of relay that closes when the redarc is open and opens when the redarc is closed or should I just ditch it and buy a dual sensing isolator

The above is contradictory so not sure what you mean... first you mention you want a way so the Redarc won't hold closed then you mention buying a SBI12 which will close the solenoid anyway


I read on here somewhere that the solenoid would hold closed if a charge was applied to the aux while the both batteries were connected and wouldn't open no matter what voltage the main drops too until the charge to the aux is removed

That is partially correct.
If the SBI12 is energised at the time the panel is connected it will hold the SBI12 energised.

What is incorrect is the "no matter what voltage it drops to" bit
The Cranker cannot drop lower than the Aux (they are interconnected after all) but what will happen is if the load exceeds the charging capacity and both batteries drop the SBI12 will deenrgise as normal and remove the parallel connection to the Cranker.

If that happens no matter what the Aux voltage does from then on the SBI12 will not reenergise UNLESS you use an SBI12 dual sense AND the Aux voltage rises above the set limit because you have a charging source connected

[mjr350]

Yea sorry. I had that backwards with the voltage drop and the canker wont drop if both are connected to the panel. I'll just confuse everyone even more if i keep going. I'll just buy a dual sensing isolator and be done with it. Might put the panel on a switch for now.

[the evil twin]

Hi guys. I have just received a 140w solar panel and i want to throw it on the roof so it's constantly changing the aux battery but I've only got an SBI12. Is there a way to hook it up so that it doesn't hold the solenoid closed. Im thinking some sort of relay that closes when the redarc is open and opens when the redarc is closed or should I just ditch it and buy a dual sensing isolator


Yea sorry. I had that backwards with the voltage drop and the canker wont drop if both are connected to the panel. I'll just confuse everyone even more if i keep going. I'll just buy a dual sensing isolator and be done with it. Might put the panel on a switch for now.

Way to go, Cobber...

These days I only use dual sense Redarcs or the Intervolt fully programmable versions, extra few bucks but heaps more versatile.

[mjr350]

Well I've worked it out without having to change the solenoid. If I only want to charge the aux battery then I turn the headlights on until the solenoid disconnects. Takes about 10 seconds to flick off. Usually I just leave it and let both batteries charge. Been two weeks now and the fridge hasn't made a dent in the battery.

[threedogs]

140 watt panel would have more than enough to keep an un opened fridge going.
I doubt very much you would be using 7 or so AH. thats a big panel

[mjr350]

Its brilliant. Ive been going for 2 weeks constant with no issues at all