Inverters
Plucka
Registered Users Posts: 130 ✭✭
Is there a difference -Using a 1500 watt inverter to produce 240 volts to power a 1000 watt kettle or a 3000 watt inverter to produce the same.Is the 12 volt consumption the same or one uses more than the other.
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There may be slight difference depending on the efficiency curve but that shouldn't be of concern,, the greater issue, when using high capacity inverters with 12V nominal, is, the high DC current encountered and the associated voltage drop, which in turn requires substantial conductors. For example if a 3000W inverter was at full capacity the DC current demand would be ~ 250A, which only iincreases as the battery voltage drops under such a 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. -
Power = Voltage * CurrentSo, in theory, a 1,500 Watt inverter will use the same amount of DC power for a 1,000 Watt kettle, as would a 3,000 Watt AC inverter.In practice, the 3,000 Watt inverter has larger switching transistors and such... So there is a fair amount of energy loss in the conversion from 12 VDC to 240 VAC...There are "curves" of inverter efficinecy... When using a only a few Watts of AC load, the 6-20 Watt "Tare" loading of the AC inverter just to "turn on" can swamp small AC loads and give you very poor efficiency (10 Watt load and 10 Watt Tare = 50% efficiencyAt higher loading many inverters can be in the 85% to 95% efficiency level.Other issue... For example it is very hard to get 3,000 Watts of energy from a 12 volt battery bank. Because of the high currents and voltage drops (using very heavy copper cables), I would suggest that you not try to pull much more than 1,200 to 1,800 Watts from a 12 volt battery bank. A 3kWatt inverter on a 12 volt battery bank at full AC loading would draw:
- 3,000 Watts * 1/0.85 AC inverter eff * 1/10.5 battery cutoff voltage = 336 Amps (12 volt bank) maximum continuous current draw.
4/0 or heavier wiring would be like 0.46 or 11.6 mm in diameter (or thicker if using heavier cable):Example of 4/0 cableWG gauge Conductor
Diameter InchesConductor
Diameter mmConductor cross section in mm2 Ohms per 1000 ft. Ohms per km Maximum amps for chassis wiring Maximum amps for
power transmissionMaximum frequency for
100% skin depth for solid conductor copperBreaking force Soft Annealed Cu 37000 PSI 0000 0.46 11.684 107 0.049 0.16072 380 302 125 Hz 6120 lbs If you want more Watts, look to a 24 or 48 VDC battery bank instead.-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset - 3,000 Watts * 1/0.85 AC inverter eff * 1/10.5 battery cutoff voltage = 336 Amps (12 volt bank) maximum continuous current draw.
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thanks Bill
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