36v Golf Cart Solar Panels

serius
serius Registered Users Posts: 11 ✭
in Solar Beginners Corner #1
Hello guys. Got a question...
I want to put a small solar panel on my 36v golf cart. I was told most panels are 12v and that i would need 3 panels to make the 36v. I was bummed then i search 36v solar panels. Found one not too badly priced.
Can i hook a 36v panel to help my golf cart? And...should i get an 80watt or a 200watt panel? Any thoughts

Also, do i need a charge controller for a golf cart?...if anyone might know

Golf cart has 6 well used T105 batteries
Thanx guys
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #2
    Yes--36 Volts is an "orphan" in solar power systems... There are some charge controllers (both PWM and MPPT) that can charge 36 VDC battery banks. In general, you need a Vmp-array >=~ 52.5 Volts (STC panel ratings). 2x Vmp~30 volt panels (pretty common for GT type panels) would work OK.

    The size of solar array you need--Depends what you want to accomplish... Just float the batteries when the cart is in storage--Or do you want to use 100% solar power to power your trips.

    More or less, the calculations would look like this (assuming 6x 220 AH @ 6 volt batteries)::
    • 43.5 volts charging * 220 AH battery bank * 1/0.77 panel+controller derating * 0.01 rate of charge = 124 Watt array "float"
    • 43.5 volts charging * 220 AH battery bank * 1/0.77 panel+controller derating * 0.05 rate of charge =621 Watt array "weekend/seasonal" charging
    • 43.5 volts charging * 220 AH battery bank * 1/0.77 panel+controller derating * 0.10 rate of charge =1,243 Watt array "nominal"
    • 43.5 volts charging * 220 AH battery bank * 1/0.77 panel+controller derating * 0.13 rate of charge =1,617 Watt array "cost effective" maximum
    The above is based on the battery bank size (voltage and AH rating). But you also need to size it based on your daily power usage (if you want the solar array to provide 100% of the energy used driving).

    As an example, lets guess you use ~1/4 of the battery bank energy every day:
    • 36 volts * 220 AH * 1/4 of bank energy = 1,980 Watt*Hours per day driving
    And using the Solarenergyhandbook for Tampa FL, tilted 28 degrees from Horizontal, the minimum winter sun is ~4.5 hours per day (December--Assuming you are using the cart in Winter).

    http://solarelectricityhandbook.com/solar-irradiance.html
    •  1,980 WH per day * 1/0.61 DC system eff * 1/4.5 hours of sun per day = 721 Watt array minimum for "daily drive"
    Anyway--some numbers/formulas to think about... Once you figure out the size of solar array you want, then we can look at the panels+charge controller that will support your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #3
    Take a look at Genasun controllers.  They make boost controllers for golf carts that can charge a 36 volt battery from a 24 volt solar panel.

    vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #4

    Put the largest 36 volt panel that will fit on the roof or three 12 volt panels that are about 1/3 size the size of the roof and will fill it up nicely. Even if you could put a 200 watt panel on there it would likely still need some time on the charger.

    I expect a "200 watt panel" on an MPPT controller to be able to support up to 2 miles of driving per day if you live in a sunny area.

    A genasun MPPT controller on 24 volts would work for a 36 volt battery but I don't think it is as efficient as using a 36 volt panel.

    You talk about driving a cart around like its a big thing where you are, my guess is you live in Florida?

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • serius
    serius Registered Users Posts: 11 ✭
    #5
    Damn thats alot of info to assimilate. I do not want to run on solar to do the driving, just help charge it when not being used. Im also not rich so would like to do this as economical as poss.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #6
    serius said:
    I do not want to run on solar to do the driving, just help charge it when not being used. Im also not rich so would like to do this as economical as poss.
    Sounds like you want just a battery maintainer.  I don't know of any inexpensive mass marketed battery maintainer for 36 volts.   If you can find some panels with high enough voltage but low enough power to not boil your batteries dry, then you can probably get by without a controller.  You will need a diode to prevent the battery from backfeeding the panels at night.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • serius
    serius Registered Users Posts: 11 ✭
    #7
    Thanx guys. Much appreciated.
    Another question. What is "positive ground charge controller"? Im lookin at maintaining RV battery (just one for now @ 98Ah). Im lookin at a renogy 100 kit but it warned about the charge controller it comes with being a positive ground controller. My RV isnt a driving one so im not sure if its grounded on the chassis. The RV version is like $100 more as that controller is a negative ground controller.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #8
    That is wierd... Not many controllers are designed for positive ground--About the only systems that use positive ground are cathodic protection systems (to prevent underground tanks and structures from corroding, telephone equipment).

    Is this the controller?

    http://renogy.com/wp-content/uploads/2014/07/PWM1030CC-Manual.pdf

    It says nothing in the manual.

    The Amazon page talks about positive ground--But I not sure I understand what/why they are saying about positive connections.

    http://www.amazon.com/Renogy-Amp-Solar-Charge-Controller/dp/B00BCTLIHC

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #9
    Positive ground is unusual. But Morningstar does not care if you use positive or negative for ground.
    serius said:
    Damn thats alot of info to assimilate. I do not want to run on solar to do the driving, just help charge it when not being used. Im also not rich so would like to do this as economical as poss.

    I figured that. Directly solar powered cars are pretty much just science experiments that are rendered immobile by a passing cloud. Regular no thrills battery electric golf carts have proven to be very useful.

    Unless you are going to do remote charging where there is no power or if you are going to attach the panel to the roof to charge all the time then you might as well just charge with grid power. Yes you can charge the battery and drive at the same time.

    I recommend attaching them to a roof, they way they are less likely to get broken or just grow legs and disappear one day.

    I just got some cheap 80 watt panels for about $100. Even then cheap isn't really that cheap.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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