Solar charging a 36V battery

rmcinnisrmcinnis Registered Users Posts: 1
I have an application where I would like to use a solar panel to maintain the charge on a 36V battery pack.

This battery pack is used in a "pedicab" like vehicle, which includes pedal assist, and tends to get driven short distances and then left to sit for 30 minutes to an hour. This cycle repeats throughout the day and into the evening. There is NO A/C main system (Grid) available at all and very little opportunity to utilize generator for recharging. The vehicle has a "roof" of sorts that would be suitable for mounting a solar panel, and I was thinking of something in the 80 to 100 watt range.

The battery back consists of 3 20 amp-hour sealed lead acid batteries.

The problem is the 36 volt system. I find lots of solar charge controllers at 12, 24 or 48 volts. Are there any that will handle 36 volts?

I had considered adding another 12 volt battery, and then have the panel charge the 12 volt which would then feed an inverter to power a 36 volt charger. But that seems horribly inefficient, more weight to haul around, more cost and more difficult to operate.



Rod

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Solar charging a 36V battery

    Welcome to the forum Rod.

    Yes, there are controllers that can be programmed for 36 Volts. There's the rub; programmed. We are talking about more expensive MPPT type controllers in the $500 range. That would be a bit ridiculous for this application.

    What you have there is three 12 Volt batteries in series. So a cheap work around would be to use three small panels with a controller each and make sure they don't share common negative or positive. For full charging you'd want a panel that can put out about 2 Amps, which would be around 35 to 40 Watts (three of them like this: http://www.solar-electric.com/so40wa12vomu.html) and three small controllers to go with them (like this: http://www.solar-electric.com/sg-4.html).

    It's not a perfect solution. The small panels cost a lot more per Watt, tend not to be the more efficient monocrystaline type, and won't charge the batteries as a whole bank but rather as three individuals. But it is better than no charging.
  • NorthGuyNorthGuy Solar Expert Posts: 1,925 ✭✭
    Re: Solar charging a 36V battery

    XW-MPPT60-150 controller can be configured for 36V, but it's probably too big for you.

    You may be able to trick a 48V or 24V controller if they have wide parameter ranges. For example, I have 48V battery bank, but I told my solar charge controller that my battery is 60V. I then lowered all the voltage settings so that they would be too low for real 60V battery, but work well for my 48V battery.

    I searched the Web, and there are some very cute 36V chargers available.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Solar charging a 36V battery
    rmcinnis wrote: »
    The problem is the 36 volt system. I find lots of solar charge controllers at 12, 24 or 48 volts. Are there any that will handle 36 volts?

    One problem you may have is finding a panel that has high enough voltage to charge a 36 volt battery. A company called Genasun makes boost charger controllers for golf carts that can charge a 36 volt battery from a panel with lower than 36 volt output.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • FarmerXFarmerX Registered Users Posts: 1
    Re: Solar charging a 36V battery

    I have a similar need, charging a 36v golf cart out of solar power. I found in my garage 3 old panels that seem to be in good shape. My tester shows 12.3 Volts (open circuit).
    What if I connect the three panels in series and connect this series to my cart´s battery bank? I don´t think I need a controller, do I ?
    Thanks.
  • PhotowhitPhotowhit Solar Expert Posts: 5,082 ✭✭✭✭
    Re: Solar charging a 36V battery
    FarmerX wrote: »
    I found in my garage 3 old panels that seem to be in good shape. My tester shows 12.3 Volts (open circuit).
    12.3 x 3 = not enough to charge a 36 volt battery, on top of that the open circuit voltage will be roughly 20% higher than the working voltage.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BB.BB. Super Moderators, Administrators Posts: 29,994 admin
    Re: Solar charging a 36V battery

    12.3 volts for open circuit is very low for a modern panel. It sounds like they may be designed for charging a ~6 volt battery. Or three in series would charge about 18 volts worth of batteries.

    At this point, you really should look at a new set of panels (and probably charge controller) if you want to charge the cart. What size battery bank are you looking at (~210 AH @ 36 volts)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Solar charging a 36V battery

    When that doesn't work I have a 36 volt 21 amp quiq battery charger I am selling cheap.
    You can use that and a generator or grid to charge your batteries.
    I used this kind of battery charger for years to charge floor scrubber machines and tugs, I also hear they are very popular for golf cart charging. They easily out lasted the batteries they charged.

    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.

  • mryimmersmryimmers Solar Expert Posts: 114 ✭✭✭
    Re: Solar charging a 36V battery
    rmcinnis wrote: »
    I have an application where I would like to use a solar panel to maintain the charge on a 36V battery pack.

    This battery pack is used in a "pedicab" like vehicle, which includes pedal assist, and tends to get driven short distances and then left to sit for 30 minutes to an hour. This cycle repeats throughout the day and into the evening. There is NO A/C main system (Grid) available at all and very little opportunity to utilize generator for recharging. The vehicle has a "roof" of sorts that would be suitable for mounting a solar panel, and I was thinking of something in the 80 to 100 watt range.

    The battery back consists of 3 20 amp-hour sealed lead acid batteries.

    The problem is the 36 volt system. I find lots of solar charge controllers at 12, 24 or 48 volts. Are there any that will handle 36 volts?

    I had considered adding another 12 volt battery, and then have the panel charge the 12 volt which would then feed an inverter to power a 36 volt charger. But that seems horribly inefficient, more weight to haul around, more cost and more difficult to operate.



    Rod

    Here is a nice 30 amp CC that may meet your needs, very happy with mine.

    http://www.roguepowertech.com/products/chargecontrollers/mppt/mpt3048.htm
    510 watt pv, TS-MPPT 60, Exeltech XP1100, XP600 & XP250 @ 24V, 4x Trojan 105RE, Trimetric 2030, Yamaha EF2400i gen.
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