Newbie Battery question

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fixitdude
fixitdude Registered Users Posts: 5 ✭
in Off Grid Solar & Battery Systems #1
New to solar. Off grid getaway mountain home.
My question is about battery voltage. The batteries were new in Oct. 2011. Deka L16
My system is doing the following and I want to know if this is normal or I have a problem.

After the batteries reach full charge and go into float stage the voltage drops after the solar panels are no linger in the sun light to keep them topped off.
The voltage at float is 28V and slowly goes down to 26V and holds after the solar panels are no longer in the sun.

These voltages are taken from the remote display. The charge LED on my remote display will stay on constantly when in float and then flash once indicating half full when the battery voltage drops.

My system DR2424 C60/W remote display DC250 disconnect 4 Kyocera 125W panels. After an evening of use the system goes into float stage around 1pm the following day on average.
I have checked all connections and they are free of corrosion.

Is this voltage drop normal? Do I have a problem?

I would think that once charged the batteries would hold enough charge to keep the LED on the remote display on constantly until you use the system and lower the voltage.

Questions welcomed if needed.
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  • DarkStar
    DarkStar Registered Users Posts: 12 ✭✭
    #2
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    Re: Newbie Battery question

    For a 24 volt system, those voltages sound just about perfect! According to the Deep Cycle Battery FAQ, fully charged will be roughly 12.6 to 12.8 for a 12 volt battery.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Newbie Battery question

    fixitdude,
    it does sound normal if i read it correctly. batteries go through highs and lows depending on where they are at as far as charges/discharges take them. charging puts higher voltages while loads subtract voltages and the limbo area of no charge/discharge also is a medium voltage point that will slowly decay even on its own.

    btw, after you've gone through the full charge and it settles to float and the led light is constantly on that subsequent discharges will pull the voltage down far enough to allow the charging process to start over again causing the single blink of the led again indicating it has started bulk charging again.
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  • fixitdude
    fixitdude Registered Users Posts: 5 ✭
    #4
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    Re: Newbie Battery question

    Thanks for your replies.
    I will try to explain what is happening a different way.
    Batteries reach float stage of 28V. Sun stops shining on solar panels. Voltage drops to 26V and holds.
    I thought that the batteries would hold enough charge that the LED would stay solid until the inverter was engaged and the voltage dropped. Then the LED would start flashing.

    The batteries are in an unheated area if that matters.

    So what is happening is normal?

    Thanks Again.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Newbie Battery question

    The Float stage is actually an "artificially high" Voltage state maintained by the charge controller while there's enough solar to do so. Once the sun goes off the panels, the Voltage level will drop whether or not there are any loads applied.

    Normal "resting" Voltage for a "24 Volt" system would be 25.5 Volts, +/- depending on the particular batteries, their over-all condition, and temperature. If you have 26 Volts that holds after charging stops I'd say you're doing good. The question then would be: what Voltage do you have the next morning after the batteries have been drawn from and charging begins? If that is above the 24 Volt system minimum again you are in good shape.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #6
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    Re: Newbie Battery question

    Sounds ok to me .If you don't have a battery monitor, you may find the addition of one will help give you an idea of the state of charge. Also can you add a temp sensor to the charger?
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • fixitdude
    fixitdude Registered Users Posts: 5 ✭
    #7
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    Re: Newbie Battery question

    Thank You All !!

    Reading your replies my system is performing fine.

    fixitdude
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  • SCharles
    SCharles Solar Expert Posts: 123 ✭✭
    #8
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    Re: Newbie Battery question

    Those batteries do sound strong, relax.
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