12V, 24V, 48V...Which?

brewer
brewer Registered Users Posts: 21 ✭✭
in Solar Beginners Corner #1
What is the best volts to run? Here's what I have. 6 220W panels, FM80 controller, 12 12V AGM batteries, and am going to get a FX3048 inverter because I want to run more things in the future=more watts. But what are the advantages/disadvantages of 12, 24, and 48?
· Share on Twitter

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: 12V, 24V, 48V...Which?

    1) rule of thumb #1: add 12V for every Kw of inverter draw. .9Kw = 12v 1.8Kw=24v anything more than 2Kw = 48V
    for some unknown reason, 36V just does not seem to exist much

    2) higher voltages = lower amps = smaller wire gauge - thin copper cable cost less.
    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 ,

    · Share on Twitter
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #3
    Re: 12V, 24V, 48V...Which?

    For small systems 12v is convenient because you can run 12v DC loads directly from the batts.
    For your system with 12 x 12V batts, 48V is the best choice so that you can minimize parallel battery banks, wire losses and maximize the amount of PV you can fit on a single controller.
    I find it difficult to justify 24v systems, seems to me that most 24v systems would be better off as 48v.
    · Share on Twitter
  • SolInvictus
    SolInvictus Solar Expert Posts: 138 ✭
    #4
    Re: 12V, 24V, 48V...Which?

    The main disadvantage of a 48 V system is that 50 V DC and above is considered a shock hazard. 48 V nominal systems normally operate above 50 V.
    · Share on Twitter
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: 12V, 24V, 48V...Which?
    stephendv wrote: »
    I find it difficult to justify 24v systems, seems to me that most 24v systems would be better off as 48v.

    The fewer battery cells, the better. If a single string at 24 volts works for your application, why have twice as many smaller cells at 48 volts?

    Also, some DC loads... DC fridges based on the popular Danfoss compressor require 12 or 24 volts.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
    · Share on Twitter
  • sunbunny
    sunbunny Solar Expert Posts: 59 ✭✭✭✭
    #6
    Re: 12V, 24V, 48V...Which?

    I had a hard time deciding what voltage to use with my 12 12v AGMs also. I finally went with 24 because the batteries are used and it would cost more to replace a 48v bank. Under 50v was also a consideration. And there are more choices at lower prices for many components at 24v.
    I don't mind spending a little more for the wiring.
    The hardest part was figuring out how to manage 6 battery strings without trying to have them all hooked up at once since more than 3 strings won't charge in an even manner. Had originally planned to use 300 amp battery bank switches but have built it using the battery string breakers as switches. It will be more work and record keeping to cycle the strings in and out but I think it will work well with AGMs since they lose less current just sitting than flooded batteries.
    I bought a lower cost inverter to start with in case I had to change my mind :)
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: 12V, 24V, 48V...Which?

    Or why I created this thread: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

    A a rule, avoid 12 Volts unless you specifically need it (i.e. RV/mobile application).
    48 Volts requires more expensive and sometimes hard-to-find fuses/breakers/disconnects (must be able to handle >60 Volts).
    · Share on Twitter

Categories