Golf Cart Solar Float Charging

oaklandpower
oaklandpower Registered Users Posts: 11 ✭
in Advanced Solar Electric Technical Forum #1
What are the pros/cons float charging a golf cart in storage? The use case is that the cart is fully charged prior to storage, put away in a building without grid access, connected to the solar float charger and stored all summer. The example users are "snowbirds" who use their carts in winter in the south and store them in the summer. The idea is to keep the batteries topped off and compensate for self-discharge by floating at ~2.25V at 25C.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: Golf Cart Solar Float Charging

    What I've heard, is to plug the regular charger into a timer, and have it charge for 1 hr a week, or 10 - 15 min a day.
    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

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #3
    Re: Golf Cart Solar Float Charging

    My guess, 1amp charger per 100 ah of capacity, put on a lamp timer set for 1 hour per day.

    Roughly the same as charging 1 day per month.

    As batteries age, set the timer to 2 or three hours as self discharge requires.

    Check resting voltage once in a while to insure batteries are over 75% state of charge.

    I use cheap chargers so the lamp timer does not confuse the micro processor with power cycling.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,023 ✭✭✭✭
    #4
    Re: Golf Cart Solar Float Charging

    ''put away in a building without grid access,''

    Gotcha! But great advice for grid access storage :p

    Ralph
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #5
    Re: Golf Cart Solar Float Charging

    For off grid, roughly 12 watts of solar panel per 100ah at 12 volts (no charge controller needed)

    For 36 volts, 36 watts per 100ah--you either need a blocking diode or a charge controller to prevent reverse current flow above 24 volt battery bank.

    Watch water levels, and put away charged. 1% panels will not recharge the batteries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Golf Cart Solar Float Charging

    use a cheap pwm controller too for you don't want accused of harming the battery to their carts.
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  • oaklandpower
    oaklandpower Registered Users Posts: 11 ✭
    #7
    Re: Golf Cart Solar Float Charging

    My test setup is a 3x12V 65Ah pack (about 1/3 the size of a full cart pack) with the solar float charger at ~40.15V. In a short time the output current falls to the <100mA range. The controller input current saturates at 1.6A which gives an max output of about .75A. I'm using a 30W 36 cell panel. I had some concern about electrolyte stratification, but I think since there is so little current flowing there should be little opportunity for gradients to develop provided the batteries are stirred up adequately prior to storage. Comments?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
    Re: Golf Cart Solar Float Charging

    float charging isn't supposed to stir the electrolyte as that is for the bulk charge stage to do. you are just maintaining batteries that are already charged are you not?
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  • oaklandpower
    oaklandpower Registered Users Posts: 11 ✭
    #9
    Re: Golf Cart Solar Float Charging
    niel wrote: »
    float charging isn't supposed to stir the electrolyte as that is for the bulk charge stage to do. you are just maintaining batteries that are already charged.

    Right Niel. To be clear I meant the cart is charged on a high power grid charger prior to storage so that the electrolyte is properly mixed.
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