I'm in the process of installing a dual battery system or having it installed as the case may be. I've done part of the work already. Some still to do. I have been told several different things about battery choices and want to know if anyone, anywhere has some knowledge and experience that can enlighten me. The things I've been told seem to be counter to each other in some cases.
First: I need to use "exactly" the same battery in both positions in the system.
Second: The batteries don't need to be the same battery.
Third: Batteries need to be of the same type and have the same charge rate so the alternator can keep them up to speed, but don't need to be the same exact size or make.
I'm going to use a Optima 34 series in the second or auxillary position. But their optima battery for the standard position on my FJ Cruiser is a larger and heavier Group 27. Since both would be yellow tops, they would be of the same type. I can't seem to find out from anywhere whether they have the same charge rate. The group 27 has a heck of a lot larger capacity and is the battery Optima recommends for my application as a primary.
Hopefully someone will have an answer.