Grp 31 AGM vs 2 GC2s

[Padgett]

Much as I would prefer the grp 31 AGM, two GC2s from SAM's looks like about the same price and have about 50% more reserve power (395 minutes at 20A vs 210 minutes @ 25.

Is this what others are seeing ? I'd be better off with 2 GC2s ? YWTK

[tentcamper]

Yep, more amps for the buck, Or you could get 2 - 12V G31 flooded cell and have about the same capacity as 2 GC2. That way if one fails you still have one 12V battery and can limp along.

But you lose the advantage of the AGM. Faster charge time and less power lost during charging, which are both advantages with solar. Also more deep cycle discharges, and less maintenance.

[Padgett]

True but I also have a different criteria: the current group 29 and my 2500W generator both fit in the rear compartment (is also vented for wet cell battery.

I just brought home two GC2s from Sams which should fit in the same 14.25" wide rear compartment and need about an inch more depth. Will need to rebuild the platform but hope to be able to still get the genny in and out.

That rear compartment size is why I didn't just buy a 3000 Honda or Yamaha or Champion, they are too wide and two grp 31s would take up too much space.

[scrubjaysnest]

1 advantage on the GC-2's is simpler wiring then a pair of 12 volt batts. Weight is about the same for true 12 volt deep cycle. AH capacity is about the same which is more important the RC. RC is important to look at for SLI, cranking, or hybrid, deep cycle/cranking batteries.
You may need to look bracing the floor underneath with the weight of batteries plus ginny if it fits. There has been 1 report of a battery going through the floor.

[Padgett]

Original battery was in a transverse slot in the floor so only had the outer skin holding particularly if someone left off the battery box (grp 29 did not fit the box, grp 31 certainly would not fit.

I had to build a platform to hold longitudinally so the gen would fit. Wanted to go to AGM since does not vent but two GC2s are the same price and have more capacity.

Even so the two are 120 lbs and gen is another 70 so puts 190 lbs in street rear corner where there was 60 before. Not great. OTOH it reduces the tongue weight slightly. Since is a vented compartment with a drain it is really a perfect place for both.

However with the solar panels adding still more weight to the rear, I am concerned about upsetting the balance.
It is all about budgets.

[tentcamper]

Not sure I follow the simpler wiring of 2-6V vs 2-12V. Both you need heavy jumpers to go from battery to battery?? 2-6v: pos-neg/neg-pos, 2-12V: pos-pos/neg-neg.

I like the idea of 2-12V more, only because if one battery fails. I could still run off the good 12V battery by disconnecting the bad battery. Where with 2-6v, if one fails. You can not run the camper on one 6V battery. It might keep you from running around trying to find battery(s) in BFE??

[Padgett]

You forgot my space constraint The compartment is 14.25" wide. With the GRP 29 I could just slip an Arizona gallon jug between the battery and the generator. The two GC2s shaves that by an inch @10" long (to get in I need to mount sideways). A Grp 31 is 13" long. As it is I am concerned that I may need to relocate the batteries to the other end of the compartment to be able to get the gen in and out.

I suppose I could stack two Grp 31s vertically but the mount would become complicated.


And that will determine where I put the solar controller which will probably be in the storage compartment accessible from the coach & under the bed. I do not want it in the same compartment as the batteries but as close as possible. May put the 400W inverter in the same place with a simple transfer switch so it doesn't try to backfill the converter.

BTW since the design fuse from the converter to the battery is 30 Amps, #10 wire should be pleanty.

Also a pair of 6v GC2s just needs one jumper, pos to neg. A pair of 12v requires 2 pos-pos and neg-neg.