Golf cart solar charging station.

bobobobo Registered Users, Users Awaiting Email Confirmation Posts: 1
I have a 36 volt ezgo golf cart. it has 6 @ 6 volt batteries. I would like to build a charging station that I can just pull up to, hook up and fully charge my cart in a single day from say a 50 % charge.  I need to know what all I need  to do this  how many and what size, kind etc of panels, charge controller type amperage etc I plan on hooking up an inverter so I can use my cart as a solar generator if the power goes out. p.s I am wondering can I have the cart hooked up to solar charger while at the same time hooked up to the inverter and drawing power from the inverter ? Thanks I am obviously new to all this but I have been doing a lot of research and could use alot of help on this one. Thanks in advance.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,740 admin
    Welcome to the forum Bobo,

    I will do a "generic" back of the envelope design first... There will be issues (like 36 VDC is not popular for AC inverter input voltage these days--12/24/48 are standard lower voltage inputs). And some other issues such as flooded cell lead acid batteries are not really able to recharge from 50-100% state of charge in one day usually--They need something like 8-10+ hours to go through bulk/absorb states--And the sun, especially in winter, is just not in the sky that many hours per day (for many places).

    But to start... First, guessing that you have 6x 6 volt @ 200 AH flooded cell batteries in series for 36 volts (many solar charge controllers can be programmed to charge a 36 volt bank):
    • 6 batteries * 6 volts * 200 AH * 0.50 (half discharged) = 3,600 Watt*hours of storage/one day to recharge
    Next, there are two calculations that we make for the size the solar array. One is based on the size of the battery bank and rate of charge. The other is based on loads per day and hours of sun per day.

    First, charging based on rate of charge... 5% can be OK for weekend/summer usage, 10-13% rate of charge is better for full time off grid usage. And 20% or so max rate of charge. 10% or greater is typically mfg suggested rate of charge:
    • 200 AH * 43.5 volts charging (aka 36 volt bank) * 1/0.77 panel+charge controller deratings * 0.05 rate of charge = 565 Watt array minimum
    • 200 AH * 43.5 volts charging (aka 36 volt bank) * 1/0.77 panel+charge controller deratings * 0.10 rate of charge = 1,130 Watt array nominal
    • 200 AH * 43.5 volts charging (aka 36 volt bank) * 1/0.77 panel+charge controller deratings * 0.13 rate of charge = 1,469 Watt array typical cost effective maximum
    And then there is sizing the array for amount of energy per day, and where the system will be installed (and seasonal variations). For an example, a fixed, tilted array, around Orlando Florida:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Orlando
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 62° angle from vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    4.29
     
    4.76
     
    5.36
     
    5.79
     
    5.75
     
    4.99
     
    JulAugSepOctNovDec
    4.96
     
    4.87
     
    4.74
     
    4.89
     
    4.55
     
    4.16
     

    Lets say you want to use 50% of battery energy every day (usually suggest 25% of an FLA battery bank per day that is charged from solar), and use 4 hours per day sun (Florida has pretty good sun in winter, perhaps not as much during summer due to afternoon thunderstorms, etc.):
    • 3,600 Watt*Hours per day * 1/0.61 of grid DC solar system eff * 1/4.0 hours of sun per day (thru December) = 1,475 Watt array "break even" on 4 hours per day of sun
    Say you pick a 1,475 Watt array--An MPPT type charge controller, the rated amperage of the controller should be:
    • 1,475 Watt array * 0.77 panel+controller derating * 1/43.5 volts charging = 44 Amp minimum rated MPPT controller
    https://www.solar-electric.com/victron-energy-smartsolar-mppt-150-45-tr-charge-controller.html

    So, you would need to find a 45 Amp (minimum) MPPT solar charge controller that can be programmed to charge a 36 volt battery bank. Should be easy to find a higher end MPPT controller that can do that (lots of options too, Internet server, most of remote battery temperature sensor, etc.).

    The bigger issue is finding a 36 VDC input AC inverter (suggest around 1,000 Watts or so maximum AC inverter rating for your 200 AH @ 36 volt bank).

    https://www.amazon.com/s?k=36+vdc+ac+inverter (a fair number of choices here--Don't know anything about them or the sellers)

    And you need a ~1,475 Watt array (your choice to size/configuration/etc.). Larger solar panels cost around $0.50 to $1.00 per Watt depending on brand/quality/source... Note that shipping & insurance can be a huge cost adder...

    Another issue is how to connect your golf cart to the charge controller/AC inverter/etc. Will the hardware be installed in the cart or at the "charging station" (reconnecting the 36 volts to the charge controller can be an issue if not done correctly. AC inverters can take some pretty heavy current--You need to have relatively heavy/short copper cables and power connector to support these loads).

    When you talk about a charging station... Do you want to charge the cart at night and drive during the day? If yes, then the "charging station" would use its own battery bank to charge from the sun during the day, and discharge into the Golf Cart at night.

    I will stop here. Questions/corrections/etc.?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,875 ✭✭✭✭✭
    Sadly, there are not many good 36V inverters around.

    Most of the better controllers can be set for 36v batteries

    Do you know the Ah spec for the golf cart's batteries ?  then we knwo what 50% is and can caculate average solar needed to recharge from 50% to 100% in one sunny 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

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

  • mcgivormcgivor Solar Expert Posts: 3,438 ✭✭✭✭✭
    Search 36v charge controller on Google, there are many results, there is one specifically designed for golf carts where the panels are installed on the roof to provide charging even when use  https://www.ebay.com/itm/Golf-Cart-Solar-MPPT-Charge-Controller-EZGO-ClubCar-Yamaha-36v-48v-charger-Panel-/283563128085 albeit expensive for what it is, finding what you need to build a charging station wouldn't be as difficult as you may think.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • just startingjust starting Registered Users Posts: 235 ✭✭✭
    My Neighbor does this, he uses 2kw of solar and a 36v inverter, it's his house bank, when he cuts wood he drives it in to the woods and plugs in a chainsaw, it has a extra axle so it's a 4 wheel drive 
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • MarkCMarkC Solar Expert Posts: 194 ✭✭✭
    A very different approach that I admittedly "stumbled" upon:

    SMA Sunny Boys (grid tied)  come with the ability to add a secure power supply that provides a 120 VAC outlet that will supply more than enough power to operate the OEM AC based chargers for most golf carts - when there is enough sun irradiance.  My Club Car (48 VDC) charger would actually "turn down" to match the sun's variability to a limited amount and shut off and then come back on when enough "sun".  
    Of course, this requires that you decide on a rather large, expensive grid tied solar system - probably 3000 watts is minimum - but many times a great investment - and in a sunny area will keep your golf cart charged most days.
    Using the golf cart batteries during an outage (or at night) is a great choice for limited energy needs - and works fine for me.  I actually have a parallel backup set of batteries for additional backup energy.  I know it's not best to mix old and new batteries, but for emergency use only,  a good choice for the multi functionality of such a system.  


    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
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