Roger Long wrote:

snip There are very inexpensive battery management and charging
systems now that charge the batteries while leaving them isolated from
each other for normal loads.



It seems Glen and I have gone down similar paths...
If I'm understanding him, both of us _suggest_ the same thing - keep
engine starting energy available in a starting battery.
It gives you both house batteries to draw down without hand starting.
It's not only about the 1-B-2 switch.
Go ahead , use one of those motorcycle size starting duty batteries
instead of another ball buster - you have the house batteries as backup
for hard starting (a second level contingency) if you ever need it.
Just get enough CCA for the job...
It's like buying a little insurance...
Three-way isolation is pretty straight forward - except for non-matching
battery banks with accelerated (smart) charging.

Or do what a large percentage of owners do - live with the dual-battery
discharge rules you suggest (and the outcomes).
As you know, you'll face lot's of compromise decisions as you finish her
out to your satisfaction (not ours).
You will probably live thru whatever decision you make as we all have up
to this point.

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