Forum Discussion

BFL13's avatar
BFL13
Explorer II
Feb 03, 2020

AGM Troubles Update

Last Fall, was asking about my AGMs crashing after seeming to be working ok up till then. Now I just found a reference to this that explains it. First link is the previous thread on this, then the link with the explanation.

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29972544/srt/pa/pging/1/page/1.cfm

Scroll down to AGM testing and remarks.

https://shop.usaclean.com/advanced-battery-tips-from-floor-equipment-experts/

"AGM testing is different than wet testing because specific gravity cannot be tested.
1.Make sure the batteries are fully charged*

** Test procedures require a 20 minute runtime because the typical battery load tester does not apply a load long enough to notice quality errors in the manufacturing of new AGM batteries.

•Suspect batteries will often give a normal voltage reading while at rest. However, the voltage will decline rapidly or will be erratic while under load. This may take 15-30 minutes before the symptoms are exhibited. AGM batteries that are failing can give the impression of good performance for an extended period of time before exhibiting a rapid voltage decline while under load.
•The resting voltage (no load) will immediately rebound so testing the battery without a load will yield “healthy” results making it appear that batteries are fine. Once a load is reapplied and the battery pack voltage is monitored, the voltage will quickly fall and yield the packs actual voltage capacity.
•Healthy batteries will decline in a linear, predictable..."
  • RLS7201's avatar
    RLS7201
    Explorer II
    Feb 04, 2020
    lc0338 wrote:
    BFL13 wrote:
    With AGMs the equivalent to equalizing is "reconditioning" at around 15.5 volts. Supposedly seldom needed unless you have been doing 50-90s or undercharging instead of getting to true full, as happens a lot with solar when it gets dark too soon.

    Trojan's guide says never equalize AGMs, but Lifeline's does. Be worth checking others to see what they say.


    Do AGM batteries need to be equalized?
    Please keep in mind that not all AGM batteries are built equally. Our batteries are hand built and have large inter-cell connections, allowing them to be equalized. ... Batteries are pretty simple. You put energy into them, they store it, and then they give you energy when you need it.Dec 19, 2018
    lifelinebatteries.com › 2015/10 › can-i-equalize-agm-batteries


    Contrary to popular belief, batteries DO NOT store energy. A charged battery has the capacity to generate electron flow. As the battery is depleted the acid is absorbed into the plates. When charging, the acid is removed from the plates and absorbed back into the water. Batteries are a chemical generator, NOT a storage device. Capacitors are electron storage devices.

    Richard
  • BFL13's avatar
    BFL13
    Explorer II
    Feb 04, 2020
    That link above also says

    " If plates are damaged, sulfated or partially gone from long use, the battery may give the appearance of being fully charged, but in reality acts like a battery of a much smaller size. This same thing can occur in AGM cells if they are overcharged and gaps or bubbles occur. What is left of the plates may be fully functional, but with only 20% of the plates left. Batteries usually go bad for other reasons before reaching this point, but it is something to be aware of if your batteries seem to test okay but lack capacity and go dead very quickly under load."

    That's what my AGMs are like, but with more than half of original capacity. Hard to measure exactly with my tests at the 20 hr rate over time. About 60% it seems.

    What I don't know is how I damaged them and if they will stay the way they are for a while so I can still use them as a 270AH bank instead of rated 450AH. Plan A is to use them and see what happens. So far so good on that. Plan B is get two more GC15s (230AH) and toss the AGMs, for a four- battery set of Wet 6s at 460AH.

    Solar helps by keeping the voltage up and hides the poor state of the batteries. Only camp on sunny days should work! :)
  • lc0338's avatar
    lc0338
    Explorer
    Feb 03, 2020
    BFL13 wrote:
    With AGMs the equivalent to equalizing is "reconditioning" at around 15.5 volts. Supposedly seldom needed unless you have been doing 50-90s or undercharging instead of getting to true full, as happens a lot with solar when it gets dark too soon.

    Trojan's guide says never equalize AGMs, but Lifeline's does. Be worth checking others to see what they say.


    Do AGM batteries need to be equalized?
    Please keep in mind that not all AGM batteries are built equally. Our batteries are hand built and have large inter-cell connections, allowing them to be equalized. ... Batteries are pretty simple. You put energy into them, they store it, and then they give you energy when you need it.Dec 19, 2018
    lifelinebatteries.com › 2015/10 › can-i-equalize-agm-batteries
  • BFL13's avatar
    BFL13
    Explorer II
    Feb 03, 2020
    With AGMs the equivalent to equalizing is "reconditioning" at around 15.5 volts. Supposedly seldom needed unless you have been doing 50-90s or undercharging instead of getting to true full, as happens a lot with solar when it gets dark too soon.

    Trojan's guide says never equalize AGMs, but Lifeline's does. Be worth checking others to see what they say.
  • 3_tons's avatar
    3_tons
    Explorer III
    Feb 03, 2020
    In my view, the weak link with AGM’s is that they can’t be equalized...FWIW, I’m now leaning towards Lithium.

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