How Can You Tell if an AGM is Really "Deep Cycle"?

We know about marine/RV batts being not so good at that compared with "real" deep- cycle batts like T-105 6v or T-1275 12v batts.

I am suspicious that AGM "deep cycle" batts might be more like marine/RV batts, especially when noting they have lead-calcium plates.

EG, this one says it has a charging rate for "cycling", but is it meant to be repeatedly deep- cycled doing 50-80s off-grid and then fully recharged when you get home to "recover" it?

http://www.wegosolar.com/products.php?product=Deka-8A27-Absorbed-Glass-Matt-92-AHr-Solar-Battery

OTOH, this one claims to be deep-cycle and the blurb says it is unlike the usual AGM standby batts. It also has charging rates for both "cycle use" and "standby use", so what's the difference--if any?

How much is just advertising like Walmart saying their marine/RV batts are 27"DC"?

http://www.wegosolar.com/products.php?product=SKR%252d125AGM-Stark-AGM-12V-Solar-Battery-Sealed-125A

Especially when that Stark batt is from the same factory (AFAIK) as this one but different labels on it?

http://www.bestconverter.com/UB121000-100-AH-Deep-Cycle-_p_293.html#.XthXKUBFxpw

I had an AGM 8D that said it was for "cycle use" and "standby use" with almost identical specs as the Stark one except more AH of course. It could not "take" my kind of usage. IMO it was more of a "standy by" battery.

This 8D also has both uses listed, but the blurb stresses its value for standby use. At least this one might be hinting at the truth?

http://www.wegosolar.com/products.php?product=Deka-8A8D-Absorbed-Glass-Matt-245-AHr-Solar-Battery

However some members here have "telecom" AGMs that work well for their usages. But we don't really know what that usage is like.

So if you are shopping for an RV use AGM and would normally get T-105s or T-1275s can you just go ahead and get the AGM versions of those batteries? Trojan says those AGMs are for the same use as the Wet versions, but should you think they are lead-calcium and not the same at all? (Trojan doesn't say if they are lead-calcium that I could find)

So what is the truth about AGM batts for RV use deep- cycling for real?
How can you tell from the specs what's what?

( Mex gave some good info in another thread related to this too, but not directly answering these questions.---one of his points was that a battery with a few thick plates weighs the same as one with lots of thin plates)

19 Replies

MEXICOWANDERER
Explorer
Jun 04, 2020
Why not finish off the very occasional topping off with a Harbor Freight 2 cycle generator and a Megawatt? You may use as much as a quart of fuel.
BFL13
Explorer II
Jun 04, 2020
MEXICOWANDERER wrote:
Here"s another wrinkle

50/90s with every seventh being a full recharge.

Chemistry is never black and white.

That's for me! I now have four of these for that work.

https://www.eastpennmanufacturing.com/wp-content/uploads/Deka-Pro-Master-Golf-Car-Flyer-0248.pdf

It was ten years ago I was posting about the "progressive capacity loss" from doing 50-90s in succession, where after about seven I didn't have enough capacity left to get through the next night.

I don't know if AGMs have more or less progressive capacity loss than Wets. I have solar now, which usually takes care of that before the seventh 50-90 for May to Oct season.

So I gather this AGM would not do my kind of deep cycling in the winter, but is more for shallow cycling with solar.

http://www.wegosolar.com/products.php?product=Deka-8A27-Absorbed-Glass-Matt-92-AHr-Solar-Battery
pianotuna
Nomad III
Jun 04, 2020
Mex,

Thanks for that parameter.
MEXICOWANDERER
Explorer
Jun 04, 2020
Here"s another wrinkle

50/90s with every seventh being a full recharge.

Chemistry is never black and white.
MEXICOWANDERER
Explorer
Jun 04, 2020
That falls within direct questions within context
BFL13
Explorer II
Jun 04, 2020
Mex said this earlier, plus the post above in this thread.

I did not ignore these, but I am unclear if they answer my questions directly, or if I have to put 2 and 2 together in some way I haven't figured out yet. :)

Posted: 06/03/20 09:00am
Link | Quote | Print | Notify Moderator

Calcium as an additive seems to accelerate hardened lead sulfate which means no removal or desulfation
Accelerate means hardening in perhaps one-tenth the time as compared to lead antimony. This is not the exact chemistry but it will suffice as being more understandable in general
Hybrid Plates is the new norm for car type RV batteries
2% antimony positive plates and calcium additive negative plates
Uses less water than high 5% antimony true deep cycle battery
Best plate paste is colloidal lead in high percentage with a minimum of premium quality binders. This means using high purity grids
Expensive paste. Expensive binders
No substitute for thick plates
Many manufacturers BS their way with fairy tales but refuse to divulge positive plate thicknesss which demands better paste, better grids, and much more quality control
More and thinner plates is much inferior and much cheaper
That makes choosing a battery by weight alone irrational
Using computer laser robotics, Lifeline safely stuffs fewer but thicker plates and thinner but higher capacity matting into their batteries
Plate and separator alignment precise alignment are hyper-critical
Acid and electrolysis eats things for a living. A thick plate LIVES longer than a thinner plate
A critical factor of a better battery is how much abuse it can withstand yet recover
Golf car batteries, how much of a fight they offer when equalizing
MEXICOWANDERER
Explorer
Jun 04, 2020
My explanation was ignored
BFL13
Explorer II
Jun 04, 2020
You do get slightly fewer AH in the same size AGM vs Wet due to the way they are built (as explained by Trojan on their site), but that aside, can you get away with using the AGM versions the same way as the Wet versions? That's one of my questions.

Scroll down to the "key characteristics" and the summary table here:

http://www.trojanbattery.com/pdf/Trojan_AGMvsFloodedvsGel_121718.pdf

Are the AGM versions lead-calcium and if so, does that mean you can't get away with it?

Just because I did not benefit from AGM for how I do things does not mean AGMs are no good for RVing as used by others.

What everyone ought to be able to do is tell what kind of AGM would work for him based on the particular specs, same as with Wets.

I can't tell whether that lead-calcium 92AH AGM 27 (linked in the OP above) is any better for RVing than a Walmart 27DC except for being easier to live with.
theoldwizard1
Explorer II
Jun 04, 2020
BFL13 wrote:
We know about marine/RV batts being not so good at that compared with "real" deep- cycle batts like T-105 6v or T-1275 12v batts.

First, if the battery advertises "cold cranking amp" (CCA) or "marine cranking amps" (MCA) I am immediately suspicious.

Second, for similar sized batteries, compare the Ah @ 20 hr rating to the T-105 and T-1275.

Third, for similar sized batteries, compare their weight. True deep cycle will always weigh more (more lead).

When you get to "odd" sized, you are on your own !

In general, "You get what you pay for !" FYI - Both the T-105 and T-1275 are available as AGM.
GordonThree
Explorer
Jun 04, 2020
Seems to be a lot of anxiety over how many thousands to spend on batteries.

The East Penn "Sam's club" AGM (4x g31 size) I bought in 2013 are still working fine, having been deep cycled regularly their entire life AND maintained only by the so-called smart charger in my Magnum.

Having paid less than $200 a piece for them I'm very happy with the return on investment.