| TV and Dry Camping [message #114128] |
Fri, 04 February 2011 00:08  |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Senior Member |
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We have a 19 inch LCD tv that is 3 years old. I was watching it on my amp meter while we dry camped in Quartzsite. It was drawing almost 4 amps. Just before Doug and I parted ways I was in his coach. He has a 19 inch also. His tv was drawing less than 2 amps. I had him put the Kill a Watt meter on it, 25 watts. Mine, 57 watts. Hmmm, no wonder I am running the batteries down 30 amp hours each night. Our tv is on from dark til bedtime, midnight or later.
So, tonight I take my Kill a Watt meter with me to Walmart. No one around so I start unplugging the tvs and checking with my meter. Bought a new one for 158 bux, same style and brand as old one. This one uses 25 watts and draws less than 2 amps on my Trimetric 2020 meter. I may just leave it on all day now and the LED lights on all night. Might be able to sell some power back to the electric companies with our solar, ha.
Anyway, if you dry camp much and watch tv you might want to check to see just how much power it is drawing. This new one is the same screen size, 19 in. but the case is much smaller physically and lighter weight.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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| Re: TV and Dry Camping [message #114140 is a reply to message #114128] |
Fri, 04 February 2011 08:01  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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Dan,
I'm not an electrical engineer, but I am in electronics so a couple of observations:
Depending on whether you have a "modified" sinewave (stepped square wave) or pure sine wave inverter, the Kill-o-watt may or may not read Watts correctly. Most electronic devices use switching power supplies and their input current is spikes at the peak of the AC voltage and near zero during the rest of the wave.
You are better reading the DC input current to the inverter (which you did),than trying to read the AC power. Case in point, I'm currently assembling the equipment for a multi-site Fire communication system. The microwave radios operate at 120Vac and I wanted to measure its power consumption. I plugged the equipment into a PowerWave meter (similar to a Kill-o-watt) and read about 40watts. Just for fun I then plugged it into a Modified sine wave inverter and guess what.. ZERO watts. The same device also read 110V and 0.37Amps.. something isn't following Ohms law. The DC input current was 4amps at 12.4V = ~50W, so about 80% efficiency. This could be the reason you measured 25Watts AC and less than 2Amps DC (2A X ~12V = 24 watts approx... about 100+% efficient inverter)
At the main site we are using a 12V 100amp N+1 power supply/charger to power everything. There is a 600w pure sine wave inverter to power some equipment which is 120VAC only IE the microwave radios mentioned above. At first I had the Motorola repeaters plugged into the Inverter as well. When keyed, the repeaters took nearly 15amps DC into the inverter for a transmit output power of 50Watts. After I wired them to 12VDC, bypassing the inverter and its internal AC (switching) power supply, it required 9.5AmpDC for a Tx output of 50.2 watts, a saving of 5.5 X 13.85(measured)volts = 76.2 watts. Hence the reason I prefer to run a device on its working voltage rather than invert it up to 120VAC then step it back down again.
Now that I have the Voters and the repeaters wired to 12vDC rather than through the inverter, the idle DC current has fallen from ~16Amps down to ~10.5Amps. This alone will increase the standby time by about 30%, however with the 3 microwave radios running that will add about 12amps so my final idle current will be about 22amps and a max of about 40amps with both repeaters up.
Moral of my story, try to run anything you can directly from 12vdc for minimum current draw from your batteries rather than through an inverter.
Your mileage may vary.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
[Updated on: Fri, 04 February 2011 08:06] Report message to a moderator |
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| Re: [GMCnet] TV and Dry Camping [message #114162 is a reply to message #114153] |
Fri, 04 February 2011 10:33 |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Senior Member |
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Gary, I did not want to advertize but it is the Sanyo 18.5 for 158.00. I cant get model # right now as the GMC is too high up for me to get in. I did send the number to Jerry Wheeler. I also checked the Visio 22 inch, for 208.00, and it was same, 25 watts.
Bruce, our first flatscreen was used on dc but I find the new ones just have the ac plug so I lose nearly 1/2 amp going through the inverter, which is on anyway so no big deal. The Kill a Watt meter would not read through my modified sinewave. The readings were taken either on ac from the wall or from the Onan.
Gene, not sure about the question about Sam. When we started traveling I had my dog named Sam with us. She is gone now I just don't have the heart to take her name off my blog introduction.
On another note, Carl S. has just put up an album of his leds on bdub's photo site. Most of his lights came from us. I think Jim K. will have these led lights in the near future and I will have a supply at Patterson, I hope. It is not often that I am so excited over a new product but these leds are very nice for anyone who dry camps. I really love being self sufficient in the coach. Now, if I can just figure out how to get the new icemaker to run on very low power I will be a real happy camper.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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