wa8yxm wrote:
A single Group 27 From Autozone assuming a MARINE/deep cycle you have less than 20 Amp Hours of usable power.. Your furnace likely draws about 10 amps all by itself. Add other stuff Lights and such) and you run out of power fast
Upgrade to a pair of GC-2, that's 220 amp hours give or take a bit, over 100 usable amp hours. over FIVE TIMES teh usable power. That's your problem.
And if that Autozone battery is not a MARINE/deep cycle.. the numbers are even worse for it.
group 27 roughly 100AH. marine, discharge to 50% with likely 50-100 cycles to 50% for cycle life, 50AH reasonable.
and how many will do 50-100 cycles in a few years? not many folks
yes furnace will draw around 8-10A. but if you don't do much dry camping, no reason IMHO to spend the bucks for a pair of GC. just get a decent marine battery or two, keep the DOD to 50% or less.
Now, if the group 27 is a starting battery, not marine, you'll kill it quick with discharges below 80%SOC, and even keeping it to 80% life won't be great. a BAD choice of batteries.
For the GC, 220AH, useable is not 100, but more like 150AH. Trojan spec's around 500 cycles to 25% SOC (75%DOD) for cycle life on the GC. close to 1000cycles to 50%SOC. and that's for the std GC. you can get double that for the renewable energy GC line.
I'd image that for all practical purposes for the majority of RV folks other GC batteries are close enough for Cycle life that cycle life isn't the life issue, just years of service.
And that cycle life to 25%SOC is reasonably accurate. Been there done that on two sets where over a 10 year and 8 year period put near 500 cycles to that DOD on them and they still were working well.
but again, which is best depends a great deal on intended use.
