A Costco Interstate GC-2 health report

[sternwake]

These low $$ 6v golf cart batteries were installed 12 to 14 months ago in a friend's RV, replacing 2 wally world group 29's in parallel, that were badly sulfated and not worthy of the attempt to revive them.

The owner does not respect any 50% rule, but they likely have not endured too much abuse. But no doubt they were used until their LEDs were noticeably dimmer, often, meaning clost to 10.5v and 100% discharged.

There is a main battery disconnect and my instructions to the owner were to plug in the RV for 3 days after getting home then disconnect batteries.

Their only charging sources are an Iota DLS-45 with iq4 charger coverter, and the RV's alternator.

The owners are going on a multi state trip, and I told them i wanted to check and equalize the batteries before they go.
I had not looked at them since I installed them, but there was No terminal corrosion
No watering was required.
Specific gravity was top of the white/ bottom of the green on my hydrometer on all 6 cells) 1.260 to 1.265

In an hour, raising voltage to as high as 16.2v in a few stages  with my power supply, specific gravity had risen to 1.275 +/- 0.003 on all cells.

It seems the Iota converter  is taking very good care of these batteries, and these batteries are apparently easy to recharge fully.   Also of No doubt is that they appreciated getting equalized at 16.2v until specific gravity maxed out.

 They were 84$ each before tax.

While the benchmark GC-2  flooded battery is the Trojan T-105, these budget GC-2s seem to be quite healthy and retaining their capacity quite well in the owner's usage/abusage. 

 A true capacity test  Means loading them at some 10.2 amps exactly for 20 hours, or how many hours until voltage falls to 10.5v at that exact load.   A True capacity test is not going to happen.

I've not personally cycled 6v GC-2s, but I went through many parallelled 12v flooded marine battreries.

My experiences with the 12v marine batteries is they are much more difficult to get the specific gravity to its maximum, requiring higher voltages applied for longer, and frequent 16 volt equalizations once their voltage started behaving poorly under load.

These GC-2s took less than 70 minutes of massaging them with progressively higher voltage before Specific gravty maxed out on all cells and very closely with each other and the job was complete

I really expected to have my power supply hooked to them for many hours with many hydrometer dippings and monitoring required, but it was quick and painless.

Anyway the benchmark Trojan  t105 flooded battery would likely easily outcycle these budget Interstate costco GC-2, and perhaps consume less total energy to recharge, but these specific GC-2 batteries are doing very well and much better than the owners previous set of 29's n parallel that saw the same usage and charging sources.

Conclusions: 
In deep cycle applications, 12v  flooded marine batteries suck donkey balls compared to  a very similar capacity of 6v GC-2 golf cart batteries in series, and the latter costs less and requires less work/maintenance. 

Not everybody requires 210Ah+ of capacity, or has the extra height required for the taller GC-2's in series , and in such cases they are stuck with 12v batteries in parallel.  

12v marine battery fan boys like to point out that one  battery fails, then one still has 12v available on the other battery.

12v flooded marine batteries can also maintain higher voltage under higher loads, such as powering a microwave on an inverter as they are designed for higher cold cranking amps.

Golf cart batteries have NO CCA rating as they were never intended to be used for cranking a 140 amp starter motor.  They were designed for long life when cycled deeply often.

but they are not immune to abuse, and abuse is consistent undercharging or resting in a discharged state.

The Iota DLS-45 converter charger plugged in for 3 days after an outing, then all loads removed from them via a master disconnect, seems like it will have these batteries last the owners Many trouble free years in their usage. The Bang for the buck factor seems quite  high.

Any questions?

[frater secessus]

Great write-up.

Are the batts charged at all during their outings (isolator, solar, generator, etc) or do they deplete over the course of the outing? How long are the outings usually?

[Blacktank]

210ah out of 2 6 volts?

[sternwake]

These batteries charge with the engime running, but other than the Iota that is the only charging source. The iota works on their generator, but the generator runs only if the Ac is required as far as I know, or if the wife requires the hair drier.
No solar.

They also use itheir RV as a Guest suite, and I rarely see it plugged in during such duty. Usually it is plugged in after a trip, or just before one.

I cannot vouch for just how long and hard the batteries are used when they go out, but they use it quite often and they just use as much electricity as they want regardless of whether the batteries are above or below 50%. I've not shared a campsite with them. No doubt the btteries are lightly worked compared to a full time van dweller, but when they are worked, they work, and are not even considered again, unless/until the interior lights go dim or the low voltage inverter alarm starts screaming.

What I can say is that I installed the Iota the same time as their previous 12v batteries. He had tried replacing the batteries himself and hooked them up wrong and smoked his Wfco Converter, So I was called and recommended the Iota DLS-45 as a replacement converter, and installed it when it arrived. I gave the same instructions then, to plug it in for three days upon return before unplugging and disconnecting the batteries. The 12v marine batteries could not handle what these GC-2s are apparently laughing at, and, they cost less.

I actually prefer the Progressive Dynamics PD-9245 converter, over the Iota, for a similar price, because of the manual override option regarding charging voltages/stages, but the look of bafflement I received when i explained the benefits of this had me think the Iota's automatic compromise, no manual input possible, better for this owner.

I really expected to have to expend much more effort in getting their specific gravity back to the maximum with longer times at EQ voltages.

I was almost, disappointed.

The Iota dls-45 on a pair of low $$ GC-2s seems, like a very good combo.

Absolute proof of this would require much more data with variables removed or accounted for, that i am not being paid to collect. I was surprised that these specific batteries appeared to be in such good condition. I wanted to share this with the members here who might still be designing their electrical system, and perhaps help some to better understand living on 12v while not destroying batteries, and perhaps to pursuade/convince those needing 200Ah+ of battery capacity, that 6v GC-2s in series are much more bang for the buck in deep cycle duty, compared to the commonly chosen parallelled 12v group 31/29/27/24 batteries.

Marine batteries proudly claim Deep Cycle on them, but they're harder to recharge fully, and cannot really handle daily deep cycling. 6v GC-2s can. Today's observations of these batteries was, to me, proof of that, and that the Iota's charge algorithm regarding the voltage stages sought and held, are a good compromise.

[sternwake]

210ah out of 2 6 volts?

 GC-2 capacity ranges from as low as 208Ah to 230 AH.  Two of them in series is still 210AH.  If they were in parallel they would have 420AH, but at 6 volts.