Could Someone Double check me.

kc6cnn
kc6cnn Registered Users Posts: 22 ✭
in Solar Beginners Corner #1
If I have an appliance that uses 120 volts and draws 325 watts, the amps drawn would be 2.7 amps.
now if I have a 600 amp hour battery system, for right now, than I could safely draw up to 300 amps from the bank.
So the appliance could run for how many hours?

Thanks trying to get by until I upgrade my system to 48 volts.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Re: Could Someone Double check me.

    The calculations depend on watts or power, Amps are current X volts + watts, so I'm assuming you currently have a 12 volt system? so basically there are some system losses inverters are 80-90% efficient, and some wire loss, so figure 400 watt load to the batteries, 400 watts/12V=@33 amps an hour so roughly 10 hours on a 12 volt battery bank, for a quick very rough guess.
    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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  • kc6cnn
    kc6cnn Registered Users Posts: 22 ✭
    #3
    Re: Could Someone Double check me.

    Thank you Photowhit. I forgot to mention it was 12 volts. So it is best to convert to watts then divide by the volts to get the amps an hour?


    so once the system is changed to 48 volts it will be 8.333 amps an hour.
    Ok, thank you again that really helps me out.
    I am going to order my panels and mppt charger hopefully this month and then changed everything over.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #4
    Re: Could Someone Double check me.

    Likely the quickest, lots of things though, your near drawing 1/20th of your battery bank per hour and with 4 batteries paralleled, you want to be sure your wiring has equal resistance. and that your using heavy wire. and how are you going to replace the amperage your taking out... 1200 watt array for 5 hours in the Texas sun with a PWM CC or maybe a 1000 watt array with a MPPT, or a generator...

    Usually try to stay in the top 20-30% of the battery bank on a regular basis for an off grid system, allowing for the 50% draw downs when things the weather isn't cooperating.
    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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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: Could Someone Double check me.
    kc6cnn wrote: »
    If I have an appliance that uses 120 volts and draws 325 watts, the amps drawn would be 2.7 amps.
    That's AC amps. Since your AC voltage is 10 times your DC voltage, multiply 2.7 by 10 to get DC amps. Thus 27 amps DC draw, but you need to add in the inverter inefficiency... thus your DC draw is a bit over 30 amps.
    kc6cnn wrote: »
    now if I have a 600 amp hour battery system, for right now, than I could safely draw up to 300 amps from the bank.
    that's 300 amphours.
    Photowhit wrote:
    Amps are current X volts + watts
    huh? that makes no sense to me.
    Photowhit wrote:
    400 watts/12V=@33 amps an hour
    400 watts/12V=@33 amps
    kc6cnn wrote:
    So it is best to convert to watts then divide by the volts to get the amps an hour?
    so once the system is changed to 48 volts it will be 8.333 amps an hour.
    leave out the "an hour"

    Sorry guys, I'm cranky this morning and can't handle the weird units. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Re: Could Someone Double check me.

    He's correct, if cranky, I was tired and sleepy(couldn't sleep).

    The "amps are current..." thing was editing, should have said "...amps are current. Amps x volts = watts.

    I also didn't complete my thought in my last post, that since your drawing at about 1/20th of the capacity, your likely to run into low voltage problems as you draw down the battery and are drawing a higher percentage of the remaining capacity. So figure a shorter run time of maybe 8 hours. Depending on the age and condition of your battery bank.
    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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