| Re: [GMCnet] 19" TV power draw through inverter [message #114412] |
Mon, 07 February 2011 08:04  |
Gary Casey
Messages: 448
Registered: September 2009
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Senior Member |
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Rob,
Thanks for posting the excellent data. Gives me hope that I can do the same.
Now for the 110-volt mini-fridge (?? watts) and the microwave (1500 watts).
Gary
After reading about Dan Gregg's TV and power draw, I decided to make some
measurements of my own.
3. The inverter efficiency, at this low load of 24 watts for a 400 watt
inverter, is 24/34 = .70 or it is about 70 % efficient overall. Considering
the standby 3.5 watts is always there if the inverter is on, and subtracting
that from the total draw of 34 watts you have a 24/30.5 = 79% efficiency. Not
bad considering the inverter only cost $25. Also note that the inverter input
voltage dropped .4 volts due to wiring and a very small auto battery supplying
the power.
--
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] 19" TV power draw through inverter [message #114436 is a reply to message #114412] |
Mon, 07 February 2011 10:38  |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
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Senior Member |
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| Gary Casey wrote on Mon, 07 February 2011 06:04 |
Rob,
Thanks for posting the excellent data. Gives me hope that I can do the same.
Now for the 110-volt mini-fridge (?? watts) and the microwave (1500 watts).
Gary
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Gary: The problem with the refrig is that they take power 24/7 so you want as low a draw as possible. Unfortunately, my investigation of small refrigerators shows that they are mostly very inefficient. Small in size, but not in energy use. Look at the yellow hang tag in any refrigerator you are considering. You will see a number in Kwh per year. Say it is 350 Kwh/year. That is 350,000 watt hours a year. Divide that by the hours in a year (8760) and you will find that on average the refrigerator takes 40 watts an hour. Add the inverter losses and you will need to put maybe 55 watts an hour into the system from the battery 24/7. 55 watts x 24 hours = 1320 watt hours. Your golf cart batteries have a hard time supplying that along with the loads of the lights and furnace and so on.
I recommend finding a refrigerator with a hang tag that says 270 Kwh per year or less. Good luck finding one.
The microwave use time is short, so even a 1200 watt microwave run for 4 minutes will only take 1200/60 = 20 watts hr. per minute or 80 watt hours total. Add the inverter losses and it will be about 100 watt hours for a 4 minute microwave run. The load will be very large for a short time, but time is the issue here.
Rob Allen
former owner of '76 x-PB
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