Originally Posted by
AK83
Just curious as to what voltage does your battery finally rest at after a few hours?
say 6 hours, or overnight or something .. not just a couple of hours.
I currently have an Century starter and some cheapo(Repco) Aux in my D1.
The Century is a supposed 720CCA 85Ah 4WD targeted ultra high performance type.
Not real sure of all their claims, but my first one didn't last 11 months. got that replaced, with same, and is now coming up to 12months old too.
When newer, my volt meter measured it's resting voltage at 12.5 - 12.6 more often than not over night.
Many times tho, having a Redarc VSR, I'd even see 12.7 over night(it depended on ambient), and as soon as I opened the door(ie. interior light come on), the Redarc would clunk, and the battery would drop to 12.6v
Now tho, it's normal resting voltage is usually 12.4v, sometimes 12.5v and on colder nights 12.3-12.2v. So obviously it's starting to fade away.
The Repco Aux battery tho, almost without fail will stay fairly steady between 12.5 and sometimes maintain 12.6v .. this is while the starter can be anywhere between 12.2 and 12.5 (now).
What I'm thinking happens is that one or the other battery tends to hold the other, less endowed battery up for longer when they're connected.
Mindful that they disconnect at 12.7v.
My plan one day will be to get an adjustable VSR, so I can set the cut out volatage myself to say 12.4, maybe even less.
As Tim says, sometimes to use the additional capacity of the starter if wanted, but mainly to maintain the connection for longer to keep both batteries 'balanced'.
On a side note(last time I checked it) we installed a Redarc in brothers D2, with twin Optimas(1 yellow, 1 red).
a few weeks ago when I last saw them, overnight, they still stay connected at 12.7v a piece .. but it was a warm night too that weekend.
the point being .. it's all well and good to want(or seem to want) to keep the starter battery isolated at a higher voltage, but if it self discharges to a lower voltage, then in reality you've just lost that charge, that otherwise may have been put to good use!
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