calculation help

kc6cnn
kc6cnn Registered Users Posts: 22 ✭
in Solar Beginners Corner #1
If I have a cabin drawing 20 amps with everything running. can someone tell me how to figure out how big of a battery bank using 24 volt or 48 volt banks I would need.
I don't know if I have given enough info, but if I am missing something post it and I will try to find out what is needed.
Thank you
Gerald
· Share on Twitter

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #2
    Re: calculation help

    Well... 20 amps * 12 volts = 240 Watts... 20 amps * 24 volts = 480 watts. Also, does the load "care" if it is 12/24/48 volts--Or are you just looking at the inverter/charge controller requirements and the loads will all be from 120 VAC?

    Also, it depends if the 20 amp load (at what voltage) is 1 hour per day or 10 hours per day.

    So, I still need to understand your loads better before I can really give you a good answer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • kc6cnn
    kc6cnn Registered Users Posts: 22 ✭
    #3
    Re: calculation help

    The loads can all run from 120 volts, some could run at 12 volts dc. but all can run from 120 or 110 ac. it is pulling 20 amps at 220 volts. I am looking to get panels, charge controller and batteries to set up a system. I may have to do without the ac as it kicks on at 13 amps and then drops to pulling 9 most the time.
    Thanks Bill I appreciate your fast response.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #4
    Re: calculation help

    How long do you want to run those loads?

    20 amps * 220 VAC * 10 hours per day = 44,000 WH = 44 kWH per day

    Are you sure? That is a heck of a lot of power for a "cabin"... I can "do the math", but it will result in ridiculously huge battery bank and solar array--Call it 1,800 AH to 3,600 AH @ 48 volt battery bank and a 16,000 watt solar array...

    Anything can be done--But is that what you are looking at (a $160,000 solar power system)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: calculation help

    Speculation: you're using a generator with a 220 Volt 20 Amp output. If so, know that this is not the same as actually using that amount of power. As Bill said, it would be a lot for an off-grid application.
    · Share on Twitter
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #6
    Re: calculation help

    20 x 220 = 4.4kW is the peak load with everything on. If you do that continuously, this is 4.4 x 24 = 105.6 kW-hours. However, you do not have everything on all the time. To size the system, you need to know how many kW-hours of these 105.6kWh you actually use on average every day. You need to measure usage of every load that you have during the day in kW-hours and then sum them up.
    · Share on Twitter

Categories