Say I have 2 of 400AH 12V DC battery banks, "A" and "B", and bankA is mobile, opportunistically charged by a HO alternator, the bankB is stationary, charged by a genset and topped up by a large solar array.
Sunny weather and alternator usage are both highly variable, there is usually no source of mains power, and a primary goal here is to minimize use of the fossil fuel engines.
When one bank is getting much more "free power" input than the other, they can be connected by a 180A "battery to battery" charger, but this unit is expensive, and is designed to charge in one direction only, from bankA to bankB.
I would like to install a switching arrangement to be able to swap the input & output wiring on the converter/charger, so I can direct current in the other direction, charging bankA from bankB when appropriate.
Ideally with a single throw, but if such a switch does not exist, I at least want a sequence simple enough to be able to train newbie users. The setup MUST protect from inadvertent direct "combining" of the two banks other than through the B2B charger, or at the very least, make doing so difficult given clear posted instructions.
The HD marine switches (from e.g. Blue Sea http://assets.bluesea.com/files/resources/sales_sheets/6823.pdf) are ideal electrically and IMO cost-effective, but the choices there are limited.
Perhaps something could be constructed from these three available designs?
3-position selector: OFF/1/2
Dual Circuit, isolated from each other, both ON or both OFF
I'm pretty sure the remaining two options are useless here:
Dual Circuit plus COMBINE
4-position selector: OFF/1/2/COMBINE