12 24 48 volt

oadkinsoadkins Registered Users Posts: 19 ✭✭
what is the advantage of a 24 or 48 volt system over a 12 volt system. thank you

Comments

  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    oadkins wrote: »
    what is the advantage of a 24 or 48 volt system over a 12 volt system. thank you

    The very biggest is that you need a proportionally smaller current for the amount of charging or inverter power.
    A close second is that it makes it easier to configure one series string instead of batteries or strings in parallel.
    SMA SB 3000, old BP panels.
  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    inetdog wrote: »

    The very biggest is that you need a proportionally smaller current for the amount of charging or inverter power.
    A close second is that it makes it easier to configure one series string instead of batteries or strings in parallel.

    To elaborate a bit, two batteries in series has the same energy storage as the same two batteries in parallel. The batteries in series will have a higher voltage which is more efficient and also be more stable.

    When batteries are in parallel it is difficult to get the current to divide equally among the parallel batteries. This leads to instability where one battery gets overcharged more often and the other gets undercharged more often. Each battery will have a shorter life than if they were balanced.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,026 admin
    For smaller systems, 12 volts is usually OK. 24 Volts is pretty common and many of the 12 volt switches/breakers/fuses will work at 24 volts too.

    48 volt fuses/breakers/AC battery chargers, etc. are more difficult to find.

    There are some other issues (if a 12 volt battery cell fails, you know right away--nothing runs at 10 volts--If a 48 volt cell fails, the system can still work at 46 volts--But the bad cell can cause problems in the bank--over heat and cause a fire, discharge other parallel strings, etc.). Also 48 volt battery banks have lots of cells to check (24 cells for a single string, 72 (thank your vtmap) cells for 3 parallel strings).

    Usually, you define your loads and power needs and then fit the battery configuration to support those needs. And, a good dividing line--If the battery bank is >~800 AH, look at going to the next higher voltage.

    Another, if your loads are around 1,200 to 2,000 Watts maximum, a 12 volt bank is usually fine. If your loads are 1,200 to 2,400 to 4,000 Watts, a 24 volt battery bank is usually a better choice. If your loads are 4,800 or larger, you should be working with a 48 volt battery banks.

    That is what's "standard" for off grid solar power today. There are other AC inverters (used in computer rooms and such) that have higher working voltages--But I would suggest that you avoid those unless you have really need them. It is difficult to find solar/AC battery chargers that work at high voltages, and working with large AH / High voltage DC Battery banks is really scary to me. Plus, the number of cells really is asking for a battery management system to monitor for bad cells/problems in wiring/charging--Another expense and complexity (and more things to maintain/go wrong).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,034 ✭✭✭✭✭
    I would make the dividing line from 24 to 48 Volts at 1,100 amp hours a commonly available 2volt L16 battery that most folks can lift (125 lb). This battery is available world wide and can be less expensive for people in really remote places. It can be cheaper staying at 24V at battery replacement time also. 48 volts is great also but you lose the 24 volt appliances and common balance of system parts are not so common in the third world.
    Try using your fingers Bill 4 x 2 =8
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • StixStix Solar Expert Posts: 31 ✭✭
    Just my small part even though I am new. I would start at 48V if you ever plan to expand. I am at 24v and wish I did 48v. I rushed into solar and paying the price. It is true you need to really think out solar before you buy. No poking fun at the ignorant guys :P
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Stix wrote: »
    No poking fun at the ignorant guys :P

    Not ignorant . .. just so darn impatient . .:p;)

    Been there .... done that . .. :D

    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
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