36 volts

Can I use 3 different solar panels (2 - 80 watts and 1- 40 watt) to make a 36 volt array (series) for charging my golf car? I have 2 golf cars that I use on my farm and can let one charge for 2 ot 3 days before I need to swap the two.
Also, what kind of charge controller do I need? What kind of battery disconnect switch do I need for the 6) 6 volt Trojans Batteries on each golf car?

Comments

  • mike95490mike95490 Solar Expert Posts: 9,015 ✭✭✭✭✭
    Re: 36 volts

    short answer, no. The panels will not even be enough to offset the self discharg of a battery bank in the car.
    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
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  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 36 volts

    Other short answer: also no.
    The chances of the Isc being close enough between the 80W and 40W panels is extremely small. You do not want to series-connect panels with widely different impedence; one of them will go "ffft" (or other cartoon noise of your choice indicating destruction).

    If they were similar; like Mike said; not enough power there to wiggle 200+ Amp hours of battery @ 36 Volts.

    Charging Voltage should be about 42-43, and you'd need at least 500 Watts of panels to do a good charge.

    Daunting, isn't it? :cry:
  • solarfoxsolarfox Registered Users Posts: 5
    Re: 36 volts

    Thanks for the info. I'll definitely give up on tha idea.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 36 volts

    my short answer is yes with a but. the series pvs will have the proper voltage i'm guessing as i assume them to be 3 12v pvs. the problem is the current will be limited to about that of the 40w pv. it will function will far less power available to the batteries than you may wish. ideally that 40w pv should be either replaced with another pv with the same imp as the 80w pvs or add another to parallel to the 40w pv to get the proper imp that way. as far as controllers go, any controller capable of 36v output is fine to use. you can go elaborate with mppt or cheaper with a pwm.

    edit to add:
    i was not reading the op correctly here for he is not looking for a 36v output, but rather trying for a 36v input with a 12v output. my bad, but what i said still is true. parallel the 12v dissimilar pvs for charging the 12v battery.
  • phred01phred01 Solar Expert Posts: 35
    Re: 36 volts
    solarfox wrote: »
    Can I use 3 different solar panels (2 - 80 watts and 1- 40 watt) to make a 36 volt array (series) for charging my golf car? I have 2 golf cars that I use on my farm and can let one charge for 2 ot 3 days before I need to swap the two.
    Also, what kind of charge controller do I need? What kind of battery disconnect switch do I need for the 6) 6 volt Trojans Batteries on each golf car?

    U will be limited to the current of the 40 w panel effectively having the performance of 3 x 40w. By your question each panel is nominal 12v. If the batteries are 12v then run the panels in // with summing diodes (3) @ 6A rating. Get a regulator that handles 160 + watts & charge the batteries in series ( assuming the batteries in ea golf cart is 1 x 6v)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 36 volts

    Let's check those numbers again.

    (2) 80 Watts = 160 + (1) 40 Watt = 200.
    200 / 43 Volts charging = 4.6 Amps (not including derating) which is 2% of a 210 Amp hour battery.

    Nope. Won't work.

    Not all at once, anyhow. If you want to get complicated with the hook-up and charge one 12 Volt section at a time it would just barely make it:

    200 @ 80% efficiency = 160 / 14.2 V = 11.2 Amps which is 5% of a 210 Amp hour battery.
    You'd probably have to recharge one section per day over 3 days, and find some way of equalizing them - probably too frequently.

    Maybe I've done the math wrong or maybe the batteries are smaller than the typical 210 (now 220) Amp hour T105's.

    But I don't think so.
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