Bad charge controller?

FirefliesNfrogs
FirefliesNfrogs Registered Users Posts: 2
in Solar Beginners Corner #1
Hello, this is my first post and I am looking for help. I had recently bought the 100 W solar panel kit on Amazon. It came with a charge controller. I had purchased 2. 6V Duracell golf cart batteries. During the daytime my charge controller says it is charging about 12.5 V and my batteries eventually charge up to 13 V. But after the sun goes down my batteries charge goes down to 12.5, 12.3 V. I do not have my inverter hooked up to my battery bank. I am very interested in solar panels and help to make a Solar battery bank. I just cannot understand why my batteries are not holding a charge. My batteries are new.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,727 admin
    #2
    Re: Bad charge controller?

    Welcome to the forum FFNF!

    Ok... Guessing that you might have gotten the Renogy 100 watt panel + 30 amp charge controller. The panel should be fine. The rated current should be around:
    Renogy 100W Monocrystalline Solar Panel
    Maximum Power: 100W
    Optimum Operating Voltage (Vmp): 18.9V
    Optimum Operating Current (Imp): 5.29A

    Don't know anything about the charge controller--But lets assume it is working.

    Next, if these are 6 volt ~ 200 AH lead acid batteries. Lets call 12.3 volts about 1/2 charge (for round numbers).

    This is winter, using the SolarElectricHandbook for Tulsa OK, fixed array:
    [h=3]Tulsa
    Average Solar Insolation figures[/h] Measured in kWh/m2/day onto a solar panel set at a 54° angle (from Vertical):
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    3.61

    4.01

    4.74

    5.20

    5.22

    5.37



    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    5.84

    5.62

    5.28

    4.75

    3.73

    3.36



    With a PWM controller the maximum charging current Imp~5.29 Amps. With 4.01 hours of sun average for February:

    5.29 amps * 4.01 hours of sun = 21.2 AH of current per day

    The battery:

    200 AH * 50% = 100 AH
    100 AH / 21.2 AH per day = 4.71 days of average sun for February

    The 200 AH battery bank with ~5 amps of charging current is about the minimum size solar panel we would recommend for charging a lead acid battery. That is OK for weekend/seasonal usage... For daily usage, a 10% to 13%+ solar array would be nice.

    If you would like to learn more about your system and how it is operating, you might want to look at getting a DC Current Clamp Digital Multi Meter, such as this one from Sears (pretty inexpensive and "good enough" for our needs).

    You should also get a decent Glass Hydrometer to measure the specific gravity of your battery bank (assuming flooded cell). If you want a really nice Hydrometer, take a look at this one.

    Read about batteries... They are the "critical part" of your system. If you leave it set at less than ~75% state of charge, it will sulfate faster (and could be dead within 6 months).

    http://www.windsun.com/Batteries/Battery_FAQ.htm
    http://www.batteryfaq.org/
    http://batteryuniversity.com/

    Electrically speaking, you want to see the charging voltage of the battery to be held at 2-6 hours or so at around 14.4 to 14.8 volts to be fully charged.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • 706jim
    706jim Solar Expert Posts: 527 ✭✭✭✭
    #3
    Re: Bad charge controller?
    FirefliesNfrogs wrote: »
    Hello, this is my first post and I am looking for help. I had recently bought the 100 W solar panel kit on Amazon. It came with a charge controller. I had purchased 2. 6V Duracell golf cart batteries. During the daytime my charge controller says it is charging about 12.5 V and my batteries eventually charge up to 13 V. But after the sun goes down my batteries charge goes down to 12.5, 12.3 V. I do not have my inverter hooked up to my battery bank. I am very interested in solar panels and help to make a Solar battery bank. I just cannot understand why my batteries are not holding a charge. My batteries are new.

    I used golf cart batteries for years. (Mine were set up for 24 volts, so compare half of my readings here).

    I would float the batteries at 27.0 volts (or 13.5 for your case) and a few hours after the sun went down, the voltage would drop to about 25.0 (or 12.5 in your case) even if there was zero load on them.

    I don't think there's anything wrong with your batteries although the charge controller could probably have a higher cutoff point if it is adjustable.
    Island cottage solar system with approximately 2300 watts of panels, 1kw facing southeast 1.3kw facing southwest. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter which has performed flawlessly since 1994. Outback Flexmax 80 MPPT charge controller four 467A-h AGM batteries. Insignia 11.5 cubic foot electric fridge 1/4hp GSW piston pump. My 32nd year.
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  • FirefliesNfrogs
    FirefliesNfrogs Registered Users Posts: 2
    #4
    Re: Bad charge controller?

    Thank you all for the help.
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