What replacement house deep cycle batteries would you buy?

[Goodspike]

First off there seems to be a misunderstanding about amps and volts and how they add up which sort of comes down to confusing multiplication with division.

.  . ..
Therefore a pair of 100 Amp Hour 12V group 31 batteries wired in parallel equals a total of 200 Amp Hours at 12V,  and a pair of 200 Amp Hour 6V GC2 batteries wired in series to get 12V also equals 200 Amp Hours.

That's the math I was at least trying to use.  Did I screw up somewhere?

 

[Gary RV_Wizard]

where the GC2 6V batteries tend to last longer due to a number of factors, one of which is the plate spacing is wider in the cases, as each case only has 3 cells, vs the similar sized group 31 having 6 cells.  This means there is more room for debris to build up before it will short across the cells, additionally other internal features of a GC2 battery are designed to maximize life

The 6v golf cart battery is indeed an example of a battery designed for deep cycling, but there are 12v batteries designed the same way.    The volume of space and lbs of lead plate needed for xxx amp-hours of quality deep cycle performance is exactly the same whether packaged as 6v or 12v batteries. Every cell of a flooded cell battery produces 2.1v and you need 6 of them to get 12v.  The amount of AH per cell depends on the size of the lead plates. The spacing and other factors needed for good deep-cycling are the same  too.  No getting around those facts.

 

[Goodspike]

The volume of space and lbs of lead plate needed for xxx amp-hours of quality deep cycle performance is exactly the same whether packaged as 6v or 12v batteries.

That's what I would suspect too.  Each cell is wider, because there are only three per battery case, but that's a different issue and I don't see how that affects performance.

 

[Utclmjmpr]

Trojan T105 in series parallel.>>>Dan

 

[Isaac-1]

3 cells per case, vs 6 cells per case for similar size cases, means plate spacing is wider, and harder to bridge and short out with the 6V GC2 battery.

 

[jymbee]

For any given battery case size, AGMs are going to have a somewhat lower Amp-Hour capacity than flooded cell batteries.  Your present NAPA flooded cell 6v GC2 yield 230 AH (total for the pair).  If you want to keep the same AH capacity in the AGMs, you will want to step up to a larger case size, either the taller GC2H AGM or the longer Group 31 12v.  2x standard size (GC2) 6v AGMs will produce 190-200 AH of power; 2x 12v Group 27 size will be nearly the same. 

6V AGMs don't enjoy the same price advantage vs 12v as do the flooded cells, so stay open to the choice of 12v vs 6v.  The bottom line is that you shop for lowest cost per AH. Changing from 6v in series to 12v in parallel is usually a trivial change, but consider that as well.

Appreciate some input as to this possibility for replacement coach batteries. A big plus is that this outfit has a location that is quite close to our next stop  and they appear to do onsite installation.

Here's what they list for deep cycles:
https://www.interstatebatteries.com/recreation-vehicles/rv-batteries/deep-cycle

Not sure whether the difference between the GC2-ECL-UTL and GC2-HCL-UTL is that meaningful or if other of their offerings might be a better choice.

Here's the specs for our current (dead apparently) batteries:
NAPA 8144
Amp Hour 230 AH
Battery Terminal Type DIN
Battery Type Deep Cycle
BCI Group Size BCI No. GC2
Height 10.875 in
Length 10.25 in

 

[Goodspike]

3 cells per case, vs 6 cells per case for similar size cases, means plate spacing is wider, and harder to bridge and short out with the 6V GC2 battery.

I don't think that's necessarily true.  It just means the cells are wider.  If the spacing were different then 6 volt batteries would weigh considerably less.

 

[Bud1]

Trojan T-105
Have 2 in my class C going on 4 years strong.

Bud

 

[decaturbob]

I bought a pair of GC2's golf cart at out local farm supply store for $90/ea 2 years ago that were on sale, no issues to date.  First thing I did was put new "fill caps" on the cells that captures almost all the water vapor back into the cells.  In 2 years, I have added less than 12 oz of water total.  That batteries always on a solar trickle charger when in storage

 

[Gary RV_Wizard]

In 2 years, I have added less than 12 oz of water total.

That doesn't seem like an unusually  small amount to me. Fairly typical, if there is such a thing. The rate of water boil-off depends on many factors, chiefly the charger algorithm, how the battery is used, and ambient temperatures.
What do you think it would have been without those new caps?

 

[NOSEMOE1956]

Assuming my Interstate house batteries would need to be changed, I replaced with lithium about 6 weeks ago. Since I purchased the lithium batteries on line, I didn't return the old Interstates. They have been sitting in my garage for the past 6 weeks. Two days ago, I checked the voltage and they are still holding a decent charge of 6.5v and 6.7v. They were purchased in April 2016 so almost 5 years old. If I hadn't purchased the lithium batteries I wouldn't hesitate to go with Interstate again. It just take a bit of care compared to AGM's but are only 1/2 the price or less.

Interstate lasted me 5 years and 4 months. Only two were bad, but replaced all six as recommended.

 

[axeman33]

This has been an interesting and informative thread to read. I have recently purchased a used RV from a dealership and it doesn't come with a battery so I have to go purchase one. I've been reading all kinds of information between lead acid (flooded cell) and AGM and I think AGM is the way I'd prefer to go simply for ease of maintenance.

One thing I've read is that AGM batteries tend to last longer than flooded cell, even with regular top ups. Has anyone else read/heard this and have an experience? I see the price difference for an AGM battery is roughly $100 more than the flooded cell, which seems steep but if I can get twice as long of a lifetime from an AGM, I dont mind spending the extra money. Short term pain for long term gain so to say.

 

[Mark_K5LXP]

AGM's can have some subtle performance enhancement over flooded but at the end of the day you won't get twice the performance or longevity based on twice the acquisition cost. The clear distinction is the lack of regular attention which for some is worth the extra premium. In terms of dollars per Ah flooded is the clear winner.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

One thing I've read is that AGM batteries tend to last longer than flooded cell, even with regular top ups. Has anyone else read/heard this and have an experience? I see the price difference for an AGM battery is roughly $100 more than the flooded cell, which seems steep but if I can get twice as long of a lifetime from an AGM, I dont mind spending the extra money.

Mark is right on target.

All "flooded cells" aren't alike in longevity, so a bit more explanation is necessary. In the context of RV house use, there are three service classes of flooded cell battery:

1. An automotive starting/lighting/accessory battery (like what is in your car)
2. Marine/RV deep cycle (a hybrid design similar to #1 but longer lasting)
3. A RV or golf car true deep cycle

Class #1 doesn't hold up well in typical RV house (deep cycling) use and most AGMs will significantly outlast them. #2 is a more robust than #1, but an AGM will still typically outlast it by a couple years. Well cared for, #3 should have a service life of 6-10 years, whereas AGMs seldom exceed 6 years. But take the "well cared for" out of the equation and an AGM will probably exceed any of the three flooded types.

The wrinkle in this broad generality is that no lead acid battery holds up well under repeated ultra-deep discharging. Discharging down to 40% (or less) capacity multiple times is going to dramatically shorten the useful life. An AGM probably fares a little better than flooded batteries under those circumstances, but it will still fail within a few years or less.

 

[Mark_K5LXP]

Deep discharges won't "dramatically" shorten battery service life. Any battery has a finite number of amp hours it will deliver over it's useful life. Whether you take that in a few big chunks or many small ones you get nearly the same number of delivered Ah. There are practical and situational reasons to limit discharge depth to a given number but battery service life isn't among them. One would be hard pressed to wear out a battery by cycling before it expires due to age, so for most any impact from depth of discharge is irrelevant. If one manages to wear out a battery before it ages out, then that is the most cost effective battery there is.

Mark B.
Albuquerque, NM

 

[PJ Stough]

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[DonTom]

They don't currently make a converter that will properly charge both lithium and lead acid batteries.

Sure they do. They use a strap or a switch. Take your pick of the type of battery.

-Don- Reno, NV

 

[Old_Crow]

Sure they do. They use a strap or a switch. Take your pick of the type of battery.

-Don- Reno, NV

Okay, that's an either/or situation. What about in an application such as mine where the converter charges both the house batteries and the chassis battery? Would I have to convert the chassis battery to lithium also?

 

[DonTom]

Okay, that's an either/or situation. What about in an application such as mine where the converter charges both the house batteries and the chassis battery? Would I have to convert the chassis battery to lithium also?

I didn't realize that some converters also charge the chassis battery. If it were me, I would probably disconnect the converter charging to the chassis battery and use lithium for the house and use separate small two amp battery maintainer for the chassis battery.

FWIW, I have a small separate solar panel to help keep my chassis battery charged. Something I installed myself.

-Don- Reno, NV

 

[Old_Crow]

Mine came with a small solar panel on top of the front a/c. Panel has seen better days and the system doesn't work. No biggie to me, as I live full time and don't store the coach for months at a time.
I'll probably stick with FLA batteries, also. I only boondock a couple of months a year(spring and fall), and it's just not worth the expense in my case.