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Old 02-10-2013, 11:49 AM   #1
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Join Date: Nov 2012
Location: Sixes, OR
Posts: 95
How long will 400AH power basic needs?

After my first post asking for input on dry camping with an electric coach produced so much helpful information, this totally raised my comfort level with electric after having a propane setup for years .I just traded my trusty 2005 Holiday Rambler Endeaver for a 2012 Itasca Elclipse 42QD that has the electric fridge and propane range. While I understand that the generator will take care of recharging the batteries when needed, and the puny 10W solar will help a little, I am curious how much time can theoretically be had from the battery powered inverter. I have the coach sitting plugged into 120VAC and am only powering the refrigerator and the various sensors etc. Under these conditions,which would be the about same as I would typically use dry camping, the power meter I put in the line shows a steady 1.3 amps of AC current, and 158Watts being used.The question I have is how much of the 400AH of available battery is consumed before re-charge is necessary? How does the external AC power being used match up with the AC produced by the inverter being powered by batteries? Am I comparing apples to apples when I see only 1.6amps from external AC source powering the basics as compared to the inverter by itself? I guess this is basically a question about inverter efficiency. Thanks for any input in furthering my RV education.

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Old 02-10-2013, 01:11 PM   #2
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GKW remember that 1amp 120v is 10amp12volt and batteries only give about 50% of amp hrs. So at 1.6 amp on 120v you will be using about 16 amps 12v and 200 amphrs will last about 12.5 hrs. So you will need to recharge each day.

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Old 02-10-2013, 01:55 PM   #3
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Thanks autofish, exactly the kind of answer I was looking for. I was missing the difference between 120VAC and 12VDC current draw. I never used the inverter much with my Endeaver, so was not up to speed with details on its operation. What a great source of information irv2.com is!
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Old 02-10-2013, 05:08 PM   #4
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To help make it simple convert all to common unit...POWER, or watts.

Multiply volts times amps to get watts.

By using watts the voltage is removed from the calculation

The load in watts at 120 VAC is the same at 12 VDC but we add some overhead for the inverter.

For inverter add 15%, so multiply by 1.15

This is the load on the Battery.

Confirm Battery capacity at load.

Determine how much of your Battery you wish to use.

Multiply the amp hour amount of the Battery by 12.8 to get the watt-hour total.

Multiply this by the percentage you determined you will use.

Now divide that by your load.

Hard to explain with phone...

If you had 100 amp hour Battery then you have 1280 watt-hours of energy stored. 12.8 volts x 100 amp hours = 1280 watt-hours

If you are limiting to 50% then you have 640 watt-hours capacity

Higher loads are less time, smaller loads more time.

Search Battery run time and you will find days of reading
Tony & Lori
1989 Country Coach Savannah SE
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