Voltage query on Dual battery RedArc Isolator

[Sonic]

I’ve got a Dual battery system with the RedArc Smart start isolator and a Red Arc Dual battery monitor in my car
But I had my starter battery go flat, so I used the blue override to start my car (as it’s designed to)
But now I’ve fitted a brand new starter battery, my battery monitor is reading 14v on the new battery (when driving ) but only 12v on the aux battery

It used to both read 14v (when driving ) and my aux battery is only 5months old

Any ideas ?

[nj swb]

I hope I'm wrong, but I think you might've killed the isolator (I did something similar with a similar product).

I believe the "over-ride" function is for when the starter battery hasn't quite got enough grunt, and the second battery "helps" - it might tip in an extra 100 Amps or so.

If the starter battery is REALLY flat (or stuffed e.g. dropped a cell) the second battery is doing the bulk of the starting - contributing maybe 300 - 400 Amps. I don't believe these isolators handle that scenario, and it kills them - the heat dissipated within the isolator is proportional to the square of the current, so 3 to 4 times the current is 10 to 15 times the heat (yes, I rounded - sue me! )

The fact that you have a brand new starter battery tells me that your old starter died, so your isolator probably was stressed by the "jump start".

[Sonic]

Sounds very much right tbh I just noticed it seems to look like it’s working but the monitor in my car is only reading 12v on the aux battery side when the car is moving, not it’s usual 14v and won’t the aux battery eventually go flat? If the isolator is stuffed?

[Morville]

Is there a fuse or circuit breaker between either battery and the Redarc isolator?
Peter

[Sonic]

Is there a fuse or circuit breaker between either battery and the Redarc isolator?
Peter

100% correct , it had blown a 60amp fuse !!!
All changed and running sweet

Thanks again

[XLS PB Challenger]

100% correct , it had blown a 60amp fuse !!!
All changed and running sweet

Thanks again

Hi,

What size cable you using with the SBI12 between the two positive terminals ?

Cheers
Paul

[Morville]

100% correct , it had blown a 60amp fuse !!!
All changed and running sweet

Thanks again

Hi Sonic, glad it is fixed. Unfortunately if you link the batteries via the Redarc to start the car particularly if the starter battery is nearly flat you will blow the 60 amp fuse every time.
Peter