Tayman - Optima sounds like a familiar name. Seems like there are two types, red top for starting service and yellow top for deep cycle. I'll want yellow top. Where should I buy?
Matt1994xj - thanks for switch info. My objective is to charge both batteries at the same time, to use the factor battery for starting services, and to use the aux battery for refrigerator. So for charge they can be paralleled but for use they must be seperate. I'll forget so I need a system that accomplishes this automatically. Now it would be nice to use the aux battery in times of need as a 'jump' start and switches, heavy wiring could be added for this purpose. But to save weight, cost, and effort - and recognizing I don't often need a 'jump' I'll skip this and simply plan to use my jumper cables that I carry anyway should the need arise.
Xjjeeper19 (Justin) Thanks for constant solenoid. Does this device come with a smart controller so that the solenoid connects the aux battery when the motor is running and alternater charging current is available, then disconnects when motor stops? If so this sounds simple.
Shogun - National Luna - is there a USA supplier? Looks $$$ but they have a complete system package. I'm thinking I can just purchase a battery isolator (transistorized gadget) and use lighter gauge wiring. But I'd really like to read 'Overland Journal' review of fridges. An Internet hunt returns a list of off-topic URL. Do you have a better description or URL? Thanks!
Lowrange2 - No, a permanently paralled aux battery would allow the main battery to service refridgerator demand and possibly discharge to the no-start point. I need aux to charge in parallel but power the refrigerator independently.
Boatwrench - wow I see $465 for a complete solution, MINUS the battery. Too much cash for me! I'll make my own battery rack. But nice stuff as you say...