12.6v max charge on solar, 13.3 on home charger?

sunsworth
sunsworth Registered Users, Users Awaiting Email Confirmation Posts: 3 ✭
in Off Grid Solar & Battery Systems #1
I have a 12v deep cycle battery and Two 50 watt solar panels with a 20a regulator.  Panels are wired in parallel and connected to regulator, battery is connected to charge regulator.  There is nothing else connected.  The maximum it charges to is 12.6.  The same deep cycle battery charges to over 13v on my plug in charger at home and maintains the charge well.  Voltage from panels is about 18v. Whyyyyyyyyyy. :neutral:
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Can you tell us brand/model of charge controller (link OK)?

    And tell us about your battery (voltage, AH rating, lead acid, AGM, or other like lithium Ion or something else)?

    If you are charging a small Lead Acid battery--The "resting" voltage of a 100% sate of charge battery will be around 12.7 or 12.8 (or higher for some AGM batteries--in the 13.1 volts or so)...

    Lead Acid batteries when they start charging will accept 100% of the charging current (within reason) up to around 80% State of charge... When the battery hits ~80-85% SoC, the charger should go into "absorb" mode and hold the charging set point voltage (around 14.2 to 14.4 for small FLA/AGM batteries). And the charger should hold 14.x volts for ~2-6 hours (the deeper the discharge, the longer time on "absorb").

    Finally (depending on the charge controller, simple controller may not have Float Charge) the charge controller will enter "float mode" and hold around (typically) 13.6 to 13.8 volts (keep the battery charged, and not "boil" it dry).

    Note--When you are setting up your system, always connect the battery bank to charge controller first, and the solar panels second (and disconnect panels first, then battery bank). Solar charge controllers use the battery to "boot" the micro processor and get configured. If you connect the solar panels first, the controller can get confused, and in rare cases even get damaged.

    Do you have any meter to measure the charging current (or display on the solar charge controller)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sunsworth
    sunsworth Registered Users, Users Awaiting Email Confirmation Posts: 3 ✭
    #3
    Sunway solar 20a is my controller https://www.bestdrillreviews.com/best-solar-charge-controller 3 on this list.

    it’s a lead sealed battery 12v.  Charges to 13,8 on home charger.

    the charging voltage displayed was about 18v.  It’s 100 watts of panels, but I don’t have a means to tell charging current.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    When the PV is connected to the battery and while the battery is charging in the early part of the day, what is the voltage reading of the PV input to the charge controller ?
    Panels may read ok voltage by themselves, but collapse when loaded
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • sunsworth
    sunsworth Registered Users, Users Awaiting Email Confirmation Posts: 3 ✭
    #5
    I think we can mark this one as solved.  I sequentially disconnected panels, then battery from controller, then connected battery,then panels.  After only an hour of direct light, we are up to 13volts.  Thanks, Bill!

    _Eric
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #6
    You are very welcome Eric.

    You really want to see around 14.2 to 14.4 volts on the battery bank, and held there for a few hours.

    Depending on about of sun you receive, the size of battery bank (AH}, how deeply discharged, etc., It may take several days (or more) to get from the 13.x voltage range to the 14.x range.

    Your charge controller, I could not find much information about it. It probably charges to strong 14.2 to 14.4 VDC and holds it there as long as the sun is up, and battery is charged, no big loads.

    13.x volts is just starting to charge your battery.

    You can find inexpensive (and very expensive) DC+AC current clamp meters.

    Here is a cheap one as an example:


    Very nice for debugging and just understanding your system.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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