After reading all the excellent advice in my previous thread (would you buy used AGMs?
), I've opted to buy four new flooded golf cart batteries rather than the questionable AGMs I was asking about before. They're about the same price -- I got the GC115's from BatteriesPlus; with a quantity 4 discount they're $100/ea. My research suggests these are relabled Deka GC15s, and the BatteriesPlus rep confirmed this. They had a better Ah/$ rating than any other size I looked at, including the GC25.
So now comes the question of how do I install them. I bought four single-battery boxes from Defender, so I think physical installation is handled, but I'm wondering about electrical. My existing system is two "banks" of one Group 27 each, wired to a 1-2-both-off switch (separate positive and negative cable for each). I do not have a separate starting battery nor do I have space for one. I have never treated these banks as separate, the switch is always either off or both. Thus I intend to wire them as a single bank. It will also ease installation of my new battery monitor (Victron BMV-700, to better obsess over my new batteries, of course), which wants a shunt in the negative lead to the bank. Does this seem like a good idea?
I'm thinking jumpers between two sets of two batteries to make them 12V, then jumpers between the 12Vs and grounds, respectively, to form them into a single bank. I'll then connect my two positive leads to the combiner switch to one "corner" of the bank, and the two negatives to the other corner. What size wire should I use for the jumpers? My system is a mix of 1/0 (or maybe 2/0) cables to the bank plus 4/0 from the combiner to the inverter/charger. I'm thinking the jumpers should be 1/0 or 2/0 but I'm not sure which. They'll be very short, probably only about a foot.