Need help designing a 24 volt solar charger for a electric 4 wheeling

ThomB
ThomB Registered Users Posts: 1
in Off Grid Solar & Battery Systems #1
I have a 24 volt 4 wheeling. It uses 3 eight volt golf caret batteries. I'd like to build a solar charging station, where I would leave the vehicle plugged in 24/7 and the charge controller would keep the batteries from over charging.
Could yo urecommend how big a system I should build, and a recommendation for a charge controller? Do i need other components besides modules, and charge controllers?

Thank you,
ThomB
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Need help designing a 24 volt solar charger for a electric 4 wheeling

    Welcome to the forum.

    The question is; why?
    The reason I ask is that the solar power for charging is going to be a lot more expensive than utility power or running a generator.

    As it is, you basically have a battery bank of 440-450 Amp hours @ 24 Volts. Nothing unusual about that and it's not difficult to deal with from a solar perspective. That's the good news.
    This is the bad news: you need a lot of panel to recharge such a bank. Approximately 1400 Watts (depending on how fast you want/need to recharge) and a 60 Amp MPPT charge controller. This would cost more than $2,000.

    What's more, it will only charge when the sun shines. Isn't that when you want to be wheelin'? :D
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    Re: Need help designing a 24 volt solar charger for a electric 4 wheeling

    I think those 8V golf cart batteries are only 160 Amps, so 160 Amps at 24V. So it might make sense if they use it on weekends at a rural camp site, campground where they don't have electric installed, though a generator might make more sense.

    More info is needed though, you'd only get one charge if you went for a full charge over a week(smaller system). But if you draw the battery down below 50% your likely to have a shortened battery life, but might get by with as little as 200-300 Watt array and a cheaper ASC or moringstar charge controller. You'd want full sun which is often a problem in a place like this. It would not recharge the battery for a second ride and if you needed a genny any way for your camping...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Need help designing a 24 volt solar charger for a electric 4 wheeling

    an aside to full charging of your batteries by solar may be the supplementation to the batteries while being used. this depends on if the 4 wheeler has a roof or not and if it can accommodate the dimensions posed by pv modules. the pv would need at least 72 cells to charge a 24v battery bank or 2 pvs with at least that many cells total. 72 cells in series allows proper charging of a 24v battery bank and the use of a simpler and cheaper pwm controller. if you have a much higher number of cells the use of an mppt controller may be warranted.

    as an example (noting that i don't know what may be typical or specific to your draws) let's say you draw 40a when moving and you opt for an astroenergy 190w mono (noticing our host does not carry this 72 cell pv anymore) this pv and a charge controller would feed about 5a back into the batteries while you are out and about in full sun during the summer. (sun nearly overhead for good flat mount production) now the draw is 35a as it would be 40-5=35. as a side benefit it will continue to charge while parked even though at a low rate of 5a/160ah=3.125%. if you could fit 2 then you're really cooking as it could possibly give enough charge back to offset the actual use depending on how long it's used and allowed to be parked in the sun.

    a pv(s) mounted on the top of the 4 wheeler would minimally take some of the strain off of the batteries' operating requirements and could keep the average soc at a higher point extending the life of the batteries.

    as to charging when back home, it will probably be impractical for an off grid charging station as that would limit you to driving it when it becomes dark out so if the grid is available then i suggest opting for a gt solar system that would use the grid itself kind of like a battery as you would pump power to it during the day (sell) and use it at night (buy back) to charge the 4 wheeler batteries.
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