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Old 05-06-2011, 20:17   #1
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Inverter Draw is it relative to the appliance using it or the wattage of the inverter

Ok so I am a beginning boat electrical guy one step up from dummy after doing a few jobs and my question is

Inverter Draw is it relative to the appliance using it or the wattage of the inverter?

So if I have a 1000w inverter is it always drawing the same amount from the batteries or is it dependent on the draw of the appliance ie my grinder drawing than my vacuum?

Logic suggests to me it will have a base load and then above that will vary with appliance.

Do tell those in the know
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Old 05-06-2011, 20:25   #2
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Re: Inverter Draw is it relative to the appliance using it or the wattage of the inve

Most inverters have a small "overhead" of 1 amp DC or so whether they are supplying any AC load or not. Then the additional DC current is dependent on the AC wattage that you are trying to drive with the inverter.

An approximate (within 10% accurate) way to calculate DC requirements is to take the wattage of the appliance, say 500 watts. Then the DC amperage is 500/(12*0.9)= 46 amps.
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Old 05-06-2011, 20:27   #3
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Re: Inverter Draw is it relative to the appliance using it or the wattage of the inve

It will supply 1000 watts if needed, total.

What is actually being consumed is based on the needs of the connected devices plus a small "base load" as you described it.
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Old 05-06-2011, 21:45   #4
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Re: Inverter Draw is it relative to the appliance using it or the wattage of the inve

Thanks guys confirmation.....always good to get confirmation of common sense and not assume.... thanks also for the calculation something I can consider and apply now

Cheers
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Old 06-06-2011, 06:32   #5
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Re: Inverter Draw is it relative to the appliance using it or the wattage of the inve

I rough figure every 11 amps DC gives me 1 amp AC @ 120volts. Allows for in-efficiency in the conversion process.
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Old 06-06-2011, 06:50   #6
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Re: Inverter Draw is it relative to the appliance using it or the wattage of the inve

You can minimize the battery drain by having the inverter switched OFF most of the time, not just stop using it. Many home gadgets like lap tops, and TVs, will run directly off of the boat's 12V system with a 12V DC to 19V DC converter/car adapter. It allows more "OFF" time for the power hungry inverter. We lived aboard for 12 years, and only used the inverter occasionally.
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