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Plucka
Plucka Registered Users Posts: 130 ✭✭
in Solar Beginners Corner #1
I have 360 amp/hr 12 volt lithium batteries outputting through a 3000 watt 240 volt inverter . When I use the 240 volt electric kettle for example the battery voltage drops from say 13,2 volts down to 12.6 volts then back to 13.2 volts when the kettle switches off .The question is are my cables too small or is this just how things work ? The cables don't heat up. Thanks
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    What are the size of the conductors feeding the inverter and where is the voltage reading taken? taking readings at the battery whilst the kettle is on would give the true battery voltage, at the inverter would be the volt drop voltage under load.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #3
    the reading is taken off the solar mppt controller
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
    The kettle may be 1000W, 1000/12= 83.3A, with known gauge and length  it would be simple to calculate voltage drop using this calculator
     https://www.calculator.net/voltage-drop-calculator.html
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #5
    it could even be 2200 watts as my kettle is .  Thats why i use gas for the kettle.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    edited September 2018 #6
    kettle is 900 watts 240 volts
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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #7
    I have know idea about the sizing of the wiring -it"s just what came with the inverter

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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #8
    The thing is why does the voltage drop and then return immediately when the kettle turns off
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #9
    The ones supplied are generally undersized using larger gauge is always better.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #10
    dont have an answer to that ..... but with lead acid that is normal. Best to measure voltage at battery though , that will be a more accurate one .
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #11
    It hasn't been a problem but I think I'll upgrade the cables because the more volts I get at the kettle the quicker it will boil and the same with the toaster
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #12
    It's always a problem using 12v nominal  at full inverter power 3000W, that's 250A.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #13
    Cancel cable upgrade.Just checked 800 watt 2 slot toaster power consumption.It uses 36 watts in the 2 minutes it takes to make toast and the 900 watt kettle boils in slightly less time using 40 watts.Solar at 8.30 am was putting in 6.5 watts in the 2 minutes taking only 14 minutes to replace the used watts not taking into account of any losses.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #14
    Maybe some confusion between watts and watt-hours? Watts is a flow rate, watt-hours is a quantity.

    Making toast (which I quite like and make regularly) takes a large flow (watts) for a short time (so not a lot of quantity - watt-hours). Having a high rate of flow though, does work better if you have a bigger "pipe" to handle the flow.

    Lower voltage means higher flow (amperage) for a given wattage, so for 12v system voltage, you want pretty big "pipes" to handle the momentarily high flow.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited September 2018 #15
    The toaster and kettle are actually reletivaly small loads based in time, this can create voltage drop on smaller battery capacity, but 360Ah lithium should have no problem supporting the current. What batteries are they, out of curiosity? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
    · Share on Twitter
  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #16
    If it came as a kit it's probably junk.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #17
    My batteries are LFP 12 volt assembled by EV Power in Western Australia
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