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BFL13's avatar
BFL13
Explorer II
Jun 04, 2020

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

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  • Veebyes's avatar
    Veebyes
    Explorer II
    Jun 04, 2020
    I am anxiously awaiting to see how my 3 year old Lifeine 4D has survived 8 months storage, unconnected to anything & with NO maintainer during that time.

    Previous periods of dormancy have usually been a little short of 6 months of no attention with no ill effect. My first Lifeline 4D had a service life of 9 years averaging 150 use nights a year.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Jun 04, 2020
    time2roll wrote:
    The key word is when it says "Lifeline" on the side or top.


    I like that.

    Frankly there are only three ways
    1: Buy from a REPUTABLE source (See above)
    2: Cut it open and run tests on the plates (Destructive)
    3: Deep cycle it several times (Also destructive if it is NOT a deep cycle battery)

    So. the bottom line is the only practical way is #1
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 04, 2020
    MEXICOWANDERER wrote:




    The retail car jar market is cutthroat.145 pound 8-D tar top batteries used to have 900 CCA. Now 1600 CCA is the rule. Can you figure out the significance?,


    Hi Mex,

    I'd guess thinner plates, and "hotter" acid (increased PH), leading to shorter life with greater corrosion.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 04, 2020
    Lead-calcium are a starter battery--but ymmv. The calcium reduces gassing, and replaces antimony, to reduce corrosion.

    I managed 9 years from marine batteries from Walmart. I think that was so because I had 875 amp-hours of them.

    If I were full time, I'd be replacing the telecom jars (they were not new), with the SiO2 I mentioned above.
  • BFL13's avatar
    BFL13
    Explorer II
    Jun 04, 2020
    I should have said "other than Lifeline brand" :) I don't think I have had my question(s) answered.

    I recently went back to a bank of four Wet 6s as my battery bank. I had AGMs last time, the 8D and two of those 27s Stark brand. I am hard on batteries, but I did the 0.5a/100AH faithfully, and all that.

    The 8D couldn't take it, and the 27s were down to 80% and 75% capacity after three years according to my 20 hr rate tests where I try for 10 hrs and 50%.

    So the AGM 27 so-called deep cycle lasted me about the same time (three years) as my set of Walmart 27DCs did. (but with a lot less hassle charging them!) I had way better luck with second hand T-1275s (my favourite batts) and wet 6s in the past, so I am back to what I know and trust.

    However, the question remains, if you did want AGMs and not Lifeline, how can you tell from the specs if they are proper deep cycle batts?
    Does lead-calcium plates mean they are not deep cycle in real life? Does "cycle use" mean only shallow cycling allowed?
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 04, 2020
    BFL13,

    I'd look carefully at SiO2 batteries instead of AGM. They share many of the attributes of LI, except they can be used at -40. Here is information the company (which is in BC) sent me.

    "The maximum 5 second surge rate is 900A for the 100Ah SiO2 batteries.
    This is higher and longer than what you can get with regular deep-cycle batteries.

    For depth of discharge you can still get more charge/discharge cycles @ 80% depth of discharge (1500 cycles) VS 500-1100 cycles @ 50% DoD for regular and premium deep-cycle batteries.
    At 50% DoD, SiO2 is rated for 2,800 cycles.

    One of the other main benefits of these batteries, is their electrolyte does not freeze, and they can be used in -40C/F weather without damage.
    Lithium cannot be charged below 0C, and flooded lead-acid can freeze and get internal ice-damage if discharged below -18C."

    Matthew Longman, CTO
    Azimuth Solar Products Inc.
    1048 Richter Street
    Kelowna, BC Canada V1Y 2K5
    Cell:250-878-0409
    Office:236-420-4228
    Toll Free:1-888-252-2452

    mlongman@azimuthsolar.ca

    www.azimuthsolar.ca

    http://www.azimuthsolar.ca/product-category/batteries/ull/


    http://azimuthsolar.ca/getting-silicon-dioxide-sio2-batteries-charging-instructions/

    Here is the pricing info:

    http://www.azimuthsolar.ca/product/12v-100ah-sio2-battery/

    The 100 amp-hour 12 volt sells for 599.00 CDN! They offer a further discount if you buy more than three jars.

    They do offer an 8D jar.
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Jun 04, 2020
    Recycled lead sucks.
    Trojan industrial and Rolls. Would not use anything but virgin lead in their flagship industrial batteries.
    It costs more to purify contaminated lead than what virgin lead costs outright.

    East Penn has their own lead smelter but it can extract just so much percentage of unwanted additives. Pure lead would cost near a dollar an ounce to achieve

    Pure lead for AGM batteries have trace amounts of Silver and tin added.

    Good golf car batteries have less contaminated grids and higher purity plate paste.

    Scrubber batteries use the same grade of lead as golf car batteries
    Industrial batteries demand superior grade grids and paste.

    The vendor I represented lucked out. He happened to encounter Filipino batteries with high grade Philippine lead and paste. He sold more than five thousand with no warranty returns. Mexican LTH brand used to be like that until economics forced them into the cheap at any cost race.

    The retail car jar market is cutthroat.145 pound 8-D tar top batteries used to have 900 CCA. Now 1600 CCA is the rule. Can you figure out the significance?,
  • MDKMDK's avatar
    MDKMDK
    Explorer
    Jun 04, 2020
    Thickness, surface area of the pure lead plates.
    So, ultimately the weight.
    The heavier/larger the battery, the better the number and depth of cycles.
    Unless it's lithium.:B

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