Okay Capn, my turn to thread-hijack
(ok not really, this is related....)
I have a (perhaps naive) question about the various isolators, separators etc and the overall "coach (rv) battery" vs. "underhood engine battery" charging circuit. Capnkurt and I were discussing this offline this morning.
Where the question comes from:
As I understand it --- regardless of how the Coach and Underhood (Van) battery are isolated or separated while the engine is *off*, they will be connected (effectively in parallel, I understand) and both charging off the same under-hood vehicle alternator while the van's engine is running.
So my question is.....
How is the available charging-voltage regulated (or modulated....or effectively "divvied up") between the two batteries? (Coach and Van)? At any point in time while they are both being charged, do they each see the *same charging voltage* applied to their terminals, or is there a component (or electrical principle at work) that varies the charging voltage to each battery, such that the "more full" battery gets less, and the "more empty" battery sees more?
It seems that the Coach battery would almost always be the most "hungry" for charge voltage...so it would be requiring high alternator voltage. And yet the Underhood Van battery would probably not need much topping off at all, most of the time (as it has no real demands made of it while the van is parked/camping somewhere) --- and wouldn't want to have too much charging voltage applied to it while the Coach battery is being brought back to charge.
Is there a provision in the circuit that automatically sends correct, specific and individual/unique amounts of available charging voltage to each of the two batteries? Or.....as I'm picturing it.....is it a somewhat crude "one voltage fits all" situation, and thus the Underhood Van battery is therefore frequently subjected to a potential "overcharge" condition during the period of time that the House Battery is being brought back up from a state of deeper discharge?
(If so --- in a van that sees its House battery regularly deep-discharged and recharged via the van's alternator circuit, it seems that perhaps the Underhood Van battery could see its lifespan shortened (or that it would frequently need its water levels checked, to be sure it didn't overheat and vent off water when it was being temporarily overcharged, during those frequent instances when the House battery was being brought back up to charge.))
Still trying to digest all of this as well,
I'm curious if the more sophisticated separators do the function of "intelligent, individual-battery specific charging voltage allocation" as I'm imagining would be ideal....or if it's a non-issue....or if even my "old school" 1990's Sportsmobile Isolator/Charging circuit is already as sophisticated as it gets, as far as applying correct charging voltage to each specific battery in the system (House vs. Underhood Van.)
(*** Thanks for the ongoing electrical enlightenment, btw...hope that these threads benefit a good number of others in the same position going forward. I've read a good number of the sticky-posts on a number of the related topics, but somehow this particular question I'm not sure I've found addressed.)