Refit: House/Starter Battery layout

[Q Xopa]

Originally Posted by john61ct

Yes the 12B switch needs to be used judiciously, but in a true emergency is much better than scrambling for jumper cables.

In this case, only room for four units, a Reserve that is rarely used is too much dead lead.

Plus the prospect expressing skepticism that Firefly G31 has less cranking oomph than the Optima, figure better going half-half on the "low SoC reserve" idea.

Not an ACR is too high a cutoff, only joins while charging.

An adjustable LVD lets the owner tweak the SoC level to balance the ideal of keeping the bank whole as often as possible, and ensuring the cranking reserve sub-bank always has plenty of oomph left after the House loads' over drawing has triggered a split.

Yes agreed a reserve bank is dead lead.
But then again so is a Starter batt most of the time. For that matter jerry cans of fuel, or a liferaft or EPIRB could also be called 'dead' weight, atleast until you need them.
LVD, sure will work. Not a regular way of doing it. It sounds a bit of a special solution to me. Im not convinced running both batts nearly down before disconnecting is a solution I like. But if thats how you want to have yours, ok.
Its getting too close to the Both battery switch position, which is bound to get left in B position flatening Both batteries. Or combining a good start batt to a depleated house bank. Lots of the Start batt will go into the flat house bank.
Why not just turn the house batt off and use the full Start to start your engine.
Just the way I do it.

[john61ct]

Originally Posted by Q Xopa

Im not convinced running both batts nearly down before disconnecting is a solution I like.

Not both, just the not-isolated House side.

And you can set the LVD to whatever voltage you like. Point is ACR is something different, always isolates except while charge is active.

[hellosailor]

linda-
Please also bear in mind that you gain about 10% of all capacities by simply switching from the overpriced Optima to *any* conventional flat plate AGM battery. The reason is that Optima's cylindrical cells are literally round pegs in a square hole, they leave large unfilled spaces in the battery "case" where flat plate design fills all of the same rectangle with active materials.
In theory spiral cells like Optima were going to be more stable, stronger, more reliable, and cheaper than flat plate. In practice? Not so much, it seems like JCI simply decided to market them as a premium product, all sizzle, no steak. And if you've already managed to get 10 years on the old AGM batteries...you obviously are doing something right!