Concerned about my 3 year old AGM marine batteries

markabnc
markabnc Registered Users Posts: 2 ✭
in Old Battery Tech Discussions #1
I have a small solar setup that has been working great for 3 years.
Morningstar Tristar MPPT 45
5 x 100 watt mono panels in series
2 Deka marine batteries in parallel - I got the marine batts because live near a lake and felt I was getting a good deal on them.  I also wanted AGM because they stay inside.

Here's my question... When everything was new I would have a resting voltage in the evening of 12.8 - 12.9 volts.
Now it is consistently 12.6.  Is this normal for older batteries.  They still seem to have the same capacity etc.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
    A resting voltage of 12.6 suggests the battery isn't getting fully charged (or possibly a measurement issue) to me.

    I'd check voltage on each battery separately as one may be getting chronically undercharged vs its twin, and require periodic remedial charging on its own.

    If both are about the same, I'd look at charging regime.  Are they getting to the recommended absorb voltage (likely ~14.5v) and staying at that voltage for 2-3 hrs in the charge cycle?
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #3
    Logically, as batteries age and get some permanent sulfation, you aren't going to get the same peak voltage (because the acid is weaker).  Trying to push it higher will only cause more wear.   There should be some corresponding capacity loss,  but you might not notice it.

    So IMO, could be lacking of charging (this is December) or aging.




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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    I'd also suspect that 3 year old marine AGM are reaching end of life.  What's the factory warranty on yours?
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  • markabnc
    markabnc Registered Users Posts: 2 ✭
    #5

    Thanks for the comments. I think the warranty was 1 year.

    I check and the charging parameters are set to the East Penn recommendations.

    And yes it has been a rainy winter.

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