Off grid system not charging batteries specific gravity for newer l16 batteries is 0

notacad
notacad Registered Users Posts: 1 ✭
in Off Grid Solar & Battery Systems #1
I have an older system 25 years old.  

24 volt system
12   6 volt L 16 interstate batteries 10 months old
The system was working great until recently
Since new renter came in, specific gravity of batteries is now 0
batteries still show 24vdc as a group
will only charge to 25.5vdc
Inverter/charger is a trace model 2425

we have double checked our specific gravity (glass tube) on a known good battery, works great

20 solar panels are 12.5 vdc, wired to produce 25vdc for input to the solar controller.  panels only providing 6amps of charge



Solar controller is custom made with no specific company name

recommendations or anyone else go through the same thing?
What trouble shooting steps would you do?

I am going to place an external charger directly to the battery pack and try to raise the specific gravity and voltage above 23.8 vdc with out the panels
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Comments

  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,908 ✭✭✭✭✭✭
    #2
    Get the generator going and report back. Keep a watchful eye on this in case there are bad batteries. You do not want a fire to add to your list.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,627 admin
    #3
    Can we have some more details?
    What is the Vmp/Imp of the panels--12.5 volt panels is not really standard (these days). And how many panels (watts).

    You need Vmp-array in the 35 to 38 volt range (ideally, for a PWM type charge controller). You want the batteries to reach Vbatt-charging to around 29 volts minimum (possibly 30-31 volts if you really need it to get the batteries charged and equalized), and hold that voltage for ~2-6 hours (probably closer to 4-6 hours with batteries so deeply discharged).

    I assume that your SG is close to 1.000 (pure water)--That is a dead cell/battery... And probably that cell/battery is not long for this world anyway (lead acid batteries do not like to be taken to zero volts per cell, and even worse is "reverse charging"--low cell voltage "goes negative").

    Given the system has worked well for for 10 months--You have two non-system things you are probably fighting... The first is the new renter--Guess that they are using more electricity than the system can produce. Second, heading into winter and fewer hours of sun per day.

    You might want to look at a Battery Monitor (Trimetric is good for the price, Victron also makes nice battery monitors):

    http://www.solar-electric.com/batteries-meters-accessories/metersmonitors.html
    http://www.victronenergy.com/battery-monitors/

    Also, roughly, where is the system located (figure out hours of sun per day by season).

    Of course, you can have some other issues (bad cell in battery, charge controller failure, wiring problem at solar array, etc.).

    In any case, as Dave says--Get the batteries charged ASAP--The longer they sit near dead, the more damaged they will become. My guess is that this bank (or at least several batteries in this bank) are going to need replacement. But hopefully the work well enough you can figure out if the rest of the system is working OK and how much power your renter/home is using at this time.

    If you do not have one yet, get a DC current clamp meter (this AC/DC current clamp DMM from Sears is not expensive and "good enough" for our needs). A current clamp meter makes it very easy (and safe) to see if each solar panel string is outputting the expected current, how batteries are sharing load/charging current, etc.

    http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    My worst nightmare would be having a renter abusing my off grid system. Generally they have no idea how the system works and could not care less about any of it, other than of course to complain when they kill the system.
    I wish you well and that you can get it going again.
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  • lkruper
    lkruper Solar Expert Posts: 115 ✭✭
    #5
    Yes, what a challenge.  I would be inclined to put them on a meter and also a low voltage disconnect at 50% DOD.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
    An actual SG of zero (actually 1.00, of course), rather than just something below the lower measuring limit of the hydrometer would seem more like dry charged batteries being commissioned using distilled water instead of electrolyte rather than a point that you could actually reach even through abuse. But I admit I have never tried it.
    SMA SB 3000, old BP panels.
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