Not staying balanced

dkpro1
dkpro1 Registered Users Posts: 16 ✭✭
in Off Grid Solar & Battery Systems #1
Have 4 12 deep cycle 2 in  Series then  Parallel for 24 volt....wont stay in balance...any ideas? Thanks 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
    Not sure what you mean by balance; specific gravity, voltage, current under load?

    Making some assumptions, I'd say check connections (including how the paralleled strings are made and wired to charge sources and loads).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    edited September 2019 #3
    This diagram shows 6 volt batteries, but the "Series then Parallel" logic is the same ...
    Did you connect the Charge Controller & Load ( + / - ) wires to opposite diagonal corners of the battery pack, as shown?

    What are the details ?
    Battery Ah = ?
    Bulk amps = ?
    Absorb volts = ?
    Equalize volts and amps and time = ?
    Is it always the same cell in the same battery?




    http://www.altwindpower.com/images/battery-series-parallel/6-volt-series-parallel-4.jpg

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  • dkpro1
    dkpro1 Registered Users Posts: 16 ✭✭
    edited September 2019 #4
    Thank you for your help my bank is wired up as per diagram above what I am finding is the 1st 12 V battery near the positive terminal from solar is filling up to 15.5 V so the charge controller is seeing the bank as full and lowering Ambridge so the 2nd battery in series will only see 13 volts after a full charge
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
    How long has this been a problem?  
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    #6
    mvas asked:

    What are the details ?
    Battery Ah = ?
    Bulk amps = ?
    Absorb volts = ?
    Equalize volts and amps and time = ?
    Is it always the same cell in the same battery?
    Details ?
    Please answer questions from message #3, see above.
    Are ALL of the  batteries identical and the same age?
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  • ElectricLove
    ElectricLove Registered Users Posts: 11 ✭✭
    #7
    There is a lot of information needed to really help here but I'll assume a few things and then say what I think could help you:

    1. I assume you bought all 4 of these batteries at the same time from the same place and they are the same make/model
    2. I assume you installed them together and never used one of them for any other purpose prior to installing
    3. I won't assume you balanced them prior to install...

    Here is what you can do now;
    1st remove them from service
    2nd test each one individually for basic functionality (is their voltage within normal limits?)
    3rd charge them all up one at a time using the same charger
    4th allow them to rest for 6hrs after charging and then check the voltage on each again.  If you can also test impedance at this point (autoparts store may be able to do this test for you)
    5th if they are all found to be in good health and in condition close to one another (similar impedance, similar voltage after resting for 6hrs after being charged to the same "stop point" by the same charger)...  Then you can wire them all in parallel and then wait 24 hrs with them in parallel.  During this time tiny amounts of current will flow between the batteries until they are all equal in resistance to that current (think of 4 barrels of water and connecting them with pipes somewhere below water level so they can balance out, eventually they'll be perfectly balanced)

    After you do the above you will have 4 balanced batteries and you can put them back into your system and assuming they are all in good health and similar health to one another the system will stay balanced for a very long time.  
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  • dkpro1
    dkpro1 Registered Users Posts: 16 ✭✭
    #8
    I found the problem to be I was charging with too much current and 1 or 2 battery was surface charging and reading at high voltage and throwing the charge controller off and not delivering enough amps to the rest of the batteries
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #9
    What is the fully charged voltage across each battery now?

    I am available for custom hardware/firmware development

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  • slavco
    slavco Registered Users Posts: 7 ✭✭
    #10
    mvas said:
    This diagram shows 6 volt batteries, but the "Series then Parallel" logic is the same ...
    Did you connect the Charge Controller & Load ( + / - ) wires to opposite diagonal corners of the battery pack, as shown?

    What are the details ?
    Battery Ah = ?
    Bulk amps = ?
    Absorb volts = ?
    Equalize volts and amps and time = ?
    Is it always the same cell in the same battery?




    http://www.altwindpower.com/images/battery-series-parallel/6-volt-series-parallel-4.jpg


    What would be the best way to wire two banks of these batteries for 24v - I currently have 8 x 6v Surrettes with a 24v system and want to ensure they're connected in the most optimal way.

    Thanks

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