Battery life

Discussion in 'Off Grid Living' started by T. Riley, Jul 10, 2020.

  1. T. Riley

    T. Riley Monkey+++ Site Supporter++

    When I installed my solar I was getting about 3,500 usable watts when fully charged before the inverter would show 10.5 volts, time to shut down. Now, 6 years later, I tested it today and I got 1,500 watts before hitting 10.5. These are VMax SLR AGM 155ah batteries. The system has be on daily all this time and up until this year tested fine. Your thoughts and help would be appreciated.
    sec_monkey likes this.
  2. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    Have you carried out any testing?
    sec_monkey likes this.
  3. oil pan 4

    oil pan 4 Monkey+++

    Of you run the bank down below 11 volts resting voltage regularly they're definitely dead after 6 years.
    sec_monkey likes this.
  4. HK_User

    HK_User A Productive Monkey is a Happy Monkey


    !0 years for float.
    Less when cycled.
    sec_monkey likes this.
  5. Seawolf1090

    Seawolf1090 Retired Curmudgeonly IT Monkey Founding Member

    Batteries do wear out as they age. Six years is pretty good life. Time to invest in new batteries.
    sec_monkey likes this.
  6. T. Riley

    T. Riley Monkey+++ Site Supporter++

    i tested the about four times a year. Just plugged a 200watt lamp into the inverter and let it run down.
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  7. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    Something a bit better is continuity of junctions.
    Output of solar etc.
    sec_monkey likes this.
  8. T. Riley

    T. Riley Monkey+++ Site Supporter++

    no testing. Just found out today. Would it be all batteries or perhaps one bad one.
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  9. techsar

    techsar Monkey+++

    Those are the same batteries I use...I keep them above 12.5 volts typically, and never let them go below 12.0v.

    I hate to say it but pulling them down below 11 volts is going to kill them (or most other batteries) prematurely.

    You can try charging them individually, then let them rest for a couple days and then noting the voltages...they should all be within about .25 volts. Mine read about 12.7 +/- .05 volts.

    ETA: make sure all of your terminals are clean and tightened to the specified torque. You would be surprised what half an ohm resistance can do under load!
    Last edited: Jul 10, 2020
  10. HK_User

    HK_User A Productive Monkey is a Happy Monkey

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  11. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    I typically get 8-10 years out of a bank of L16HDs... For my new Place i have 16 new L16HDs coming and am going to a 48Vdc Battery Bank Voltage & a 5.5 Kw Inverter/Charger system... This will give me 800AmpHours of 48Vdc, with a 4Kw backup Inverter/Charger in hot Standby... At the Old place I had a 24Vdc System with 1200AmpHours & a 4Kw Inverter/Charger and it cycled from Float to recharge to Float, twice a day, and the history of Battery Banks over the last 30 years about 8-10 years, for a loss of 25% of Battery Capacity, at which time they were replaced, and the old Batteries were moved to Hot Standby for the Radio Systems and Domestic Water Pumping Systems... and those old replaced Batteries were returned for Core Charges...
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  12. Cruisin Sloth

    Cruisin Sloth Special & Slow

    What is your battery configure ?
    Series / parallel ? voltage of inverter etc

    use a volt meter DVM on Voltage drops at all connections BEFORE YOU DO ANY MUCKING ..

    Best to test and find the problem and retest to know you have licked the problem ..
    After that , you can find a battery shop who can load test the battery one at a time or ??
    Depends on your setup .
    We know nothing of how things are hooked up.




    Im 48 VDC and have my stop voltage set at 12.4 VDC as the AGS takes over
    Last edited: Jul 10, 2020
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  13. Big Ron

    Big Ron Monkey++

    I think the batteries are toast. I have LIFEPO4 batteries set up at 48volts. They are a better but more expensive kind of battery.
    HK_User likes this.
  14. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    Submarine batteries, which is what I am most familiar with, can be abused time and again but we did meticulous preventive maintenance as well part of the PMs was equalizer charges. Daily watch standers took gravities of pilot cells, electrolyte height and temp as well each cell could be remotely read for voltage. We had the ability to jump out cells to keep the over all health of the battery in the best condition possible.

    Our battery was our life.
    T. Riley likes this.
  15. T. Riley

    T. Riley Monkey+++ Site Supporter++

    12 volt, 9 100w panels, 4-155ah batteries floating. Batteries put in service April 2015(2) and Nov 2014(2).
    HK_User likes this.
  16. TnAndy

    TnAndy Senior Member Founding Member

    Any battery has a 'depth of discharge' cycle rating. You do 20% DOD, you get so many cycles.
    You do 30%, get less number of cycles. 50%, even less.......often far less than half the number at 80%. By regularly running them down to 10.5v, you've basically run them down to NOTHING.....ZERO......and if you did that on a regular basis, it's a testament to the quality of the battery you have that you get ANYTHING of it at this point.

    Don't bother testing......go battery shopping, and reset your inverters cut off voltage to something a lot higher than 10.5

    HK_User and techsar like this.
  17. OldDude49

    OldDude49 Just n old guy

    get myself in trouble here?

    Battery Lives Matter? :D:D:D
    BenP, oldawg, Tully Mars and 5 others like this.
  18. T. Riley

    T. Riley Monkey+++ Site Supporter++

    At $350 each they sure do. Any suggestions on new batteries about that price range? Any use for the used ones?
  19. arleigh

    arleigh Goophy monkey

    My own system is a bit different than most.
    Trojan 6 volt deep cycle batteries paired to 12 volts and each pair on its own switch to isolate each pair for joining the bank or isolating if there is a problem. I would test each pair regularly and if I did not have the time work on them I simply switched off that pair for another time. switching also allows me to switch through the meters. Every single component is on a 3 position switch, online, offline, and test.
    The bigger the bank the more important switching becomes because one battery weak and undetected can draw the whole system down.
  20. T. Riley

    T. Riley Monkey+++ Site Supporter++

    Is there a way to test each individual battery to determine if one is the problem. Perhaps a load test?
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