BAD Battery?

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Bigwooo
Bigwooo Solar Expert Posts: 62 ✭✭
in Off Grid Solar & Battery Systems #1
I have 14 - Concorde 212 amp AGM batteries. I noticed that on my Trimetric meter the "days since charged" number was steadily increasing. Usually as summer approaches, we use more power so I have to increase the absorb time to compensate, however my daily amp use had not been increasing. Over the last several weeks I've been using an average of 250 amps per night between charge cycles and the absorb time is normally 4.2 hours to meet an absorb end amp criteria of 15 amps. I found that yesterday, even after 7 hours of absorb, the system was not dropping below 17.

Yesterday I felt the batteries and all were nice and cool except one that was warm to the touch. After discharging last night, I removed the battery that was warm yesterday. All my other batteries read 14.6 volts, this one read 14.53. Not that much lower, but when I attached a 3w 12v light bulb it dropped to 14.4 volts. Trying the same on one of my other batteries the voltage didn't change when I hooked up the 3 watt bulb.

I'll know more when the absorb cycle ends today if the absorb amps drop to 15 amps in a reasonable amount of time.

The voltage on the battery I pulled didn't seem THAT much lower than the others. Does this sound like a bad battery to you?
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  • stmar
    stmar Solar Expert Posts: 370 ✭✭✭
    #2
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    Re: BAD Battery?

    I just replaced my 12 volt Concorde AGM batteries, I went with 6 volt 400 ah Lifeline AGMs. When I took the 4 old batteries to be tested 3 were good and one was weak according to the guy that tested them, it was at a local service center that does my vehicle maintenance. I tested the voltage, no load, and 2 were 13 volts and 2 were 12.9 when I took them out. A few weeks later they were about the same, within a tenth, even the "weak" one, so I would say that you probably need to have it tested to see if it is the weak link in your bank.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #3
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    Re: BAD Battery?

    When batterys get old loike that, you generally have two choices, take your chances and replace the whole bank, or, load test each cell individually. If you have an old 12v car inverter laying arround, fully charge them, then run a C10 load and time each one til it reachs say 12V or some predetermined LVD threshold. There are automotive type load testers that put a high momentary current on the battery, and measure the voltage drop to more or less determine the internal resistance. Which is kind of what you are doing but 3W wont tell you much i guess.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
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    Re: BAD Battery?
    Bigwooo wrote: »
    The voltage on the battery I pulled didn't seem THAT much lower than the others. Does this sound like a bad battery to you?

    Yes, it sounds bad. Do you have all 14 batteries in parallel? --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #5
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    Re: BAD Battery?

    Concorde's lineup of AGM batteries are one of the very few that allow for EQualizing, BUT you must do it correctly, and only when it calls for it. They call it conditioning in the application manual. (SunXtender, Lifeline, etc)

    What you are describing sounds like it could use this, and full details on how to do it are in the manual.

    Could it also be that this battery does not need conditioning, but the wiring infrastructure to it may be going high-resistance? Hopefully you are not doing a simple "ladder" connection charging from one end of the string either...

    Although Concorde allows for an EQ/Conditioning charge, it is NOT part of a daily or even periodic regiment - to be used only sparingly.
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