Please note that some Wally world batteries are rated using the 5 or even 1 hour rate instead of the standard 20 hour rate.
A battery rated at 120 A/h at the 1 hour rate might only read 100 A/h at the 20 hour rate.
Walmart dishonesty, and trickery.
In 2007 I bought 3 marine batteries at walmart, same age size, everything.
First battery failed at 13 months with a shorted cell, second at 23 with a highly resistive cell, the third was then delegated for engine starting duties only and lasted another 5 years.
It is not easy to acquire a true deep cycle 12v battery. The larger TDC 12v's are a bit compromised as they are acid starved . They have shoved so much lead inside what was originally designed to be a very high CCA rated starting battery case.
An analogy would be like a drag race car, repurposed to be a highway cruiser trying to get max MPG.
The group 27, 29 and 31 size batteries are not much different in size at all, yet will have capacity ratings from 95 to 130 amp hours and weights anywhere from 48 to 68 lbs.
It seems the higher the capacity crammed into the same Jar, has issues requiring higher voltages for longer to return the specific gravity to the maximum.
I have a group 31 USbattery, a true deep cycle, and I have my voltage setpoints at 14.9v absorption and 15.3v float, and this is still not enough to max out the SG daily. It can sit at 15.3v for hours each day and not max out. I have to apply 16v every 2 weeks for approximately an hour to do so and to get any performance from this battery. I read about the same issues with Trojan 12v deep cycle batteries in this size range. These recharging voltages are well outside the oft published figures and outside most charging sources capabilities. If I could not reprogram my solar controller to go this high, this battery would have been toast by now.
One former battery/ alternator engineer I correspond with says that these lower rated large 12v jars will likely perform better for longer than the higher capacity rated jar, which is opposite the general more is better philosophy. He says the group 27,31 and 34/78 batteries are problem size batteries and define the ability of any battery manufacturer to 'get it right' when a deep cycle design is attempted to be shoehorned into these Size cases/jars. And apparently few do.
Golf cart batteries were originally designed long ago around deep cycling and are not just a large starting battery jar/case with "deep cycle" internals crammed inside like so many 12v jars are.
GC batteries are much easier to return to max SG( specific gravity) requiring lower voltages and durations at those voltages and will better match the algorithms of most commonly available charging sources.
Lifespan on the deeply cycled battery is directly proportional to how easy it is to return the SG to the maximum when recharging. Some batteries require lots to return them there, others not so much. The GC's are not so much.
Verify with a hydrometer to see how well your charging sources are doing. It is extremely enlightening, and a bit depressing too, when one finds out that their recharge sources are not doing the job very well.
Also annoying when one needs to apply high voltages every so many cycles, and has no charging source capable of reaching the mid 15's.
I reprogram my solar controller to goto 16v when needed, and unfortunately this is every two weeks.
