Small RV for remote camping - inverter question

Riptide
Riptide Registered Users Posts: 3
in Solar Beginners Corner #1
Most of my loads are small 12 volt LED lighting and draw very little power. My real challenge is my CPAP unit. This machine has a DC option that while nice will not power the humidifier and while this has a low power draw I want to use the unit on 120 volt so it will heat the water in the humidifier.

I have been monitoring my average usage on a Killowatt brand meter and usage over a 7 hour period goes from a low of .18 up to .22 kilowatts (dry air requires more power) on 120 volt single phase house current. My RV will be using a pair of 6 volt golf cart batteries wired in series to both my 12 volt panel and a true sine wave inverter (per the mfg specs I can't use a modified sine wave with this unit). I am planning on using an inverter in the 250 to 300 watt range since it is never going to be connected to any large loads. I know there will be some efficiency lost to the inverter but it seems worthwhile to power the device that lets me sleep in comfort.

I know this may be a pretty basic question but if I do it right it will let me get away from the crowded RV campgrounds.

Thanks,
Kerry
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Small RV for remote camping - inverter question

    Welcome to the forum.

    I assume you mean the K-A-W indicates 220 Watt hours used in that 7 hour period? (If it's 220 Watts for 7 hours you have a big problem.) That's not too hard to supply 220 Watt hours from 12 Volts. It's only about 20 Amp hours. This would have to be figured in with your other loads of course to get total needed battery capacity.

    On the whole, you've got 220 Amp hours @ 12 Volts and that can be up to about 1.2 kW hours. How that works out with your total load demand is up to you to determine.

    You probably would want one of the Morningstar 300 Watt inverters for this. Pretty nice unit and great customer service. They do need to be "hard wired" though; no built-in outlets. Other options would be the Samlex sine wave units which do have built-in plugs. Samlex units: http://www.solar-electric.com/stalun.html Morningstar: http://www.solar-electric.com/mosu300wasiw.html

    Be wary of "no name" brands and MSW units. Not worth the money in my opinion.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: Small RV for remote camping - inverter question

    Get the Morningstar, and wire a cord on it if you need non hard wired outlet.

    I still recommend this inverter even though mine failed the other day,, but it has been in 24/7 service for 5 years. I think that these earlier production units may have had questionable FETs according to some anecdotes.

    Tony
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  • Riptide
    Riptide Registered Users Posts: 3
    #4
    Re: Small RV for remote camping - inverter question

    I had suspected I did not word my question well. Yes, that would 220 watts total used in 7 hours. so at about 20 Amp hours that would give me the flexibility to allow for a couple of low solar production/rainy days with out cracking my plan to stay to less than 40 to 45% of my battery total.

    Thanks for the recommendations on the inverters and the links. I want to avoid wasting money on noname junk since this RV is going to be built to last several years.

    Thanks again.
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  • Riptide
    Riptide Registered Users Posts: 3
    #5
    Re: Small RV for remote camping - inverter question
    icarus wrote: »
    Get the Morningstar, and wire a cord on it if you need non hard wired outlet.
    ...
    Tony

    a plug is not what I need anyway (I would just have to wire a plug on to the cable to plug into the Inverter) since this will run to a boxed in outlet at the other end of the RV where I would mostly only run the CPAP anyway.

    Thanks,
    Kerry
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #6
    Re: Small RV for remote camping - inverter question

    just remembered that there are several other CPAP threads ( 28 of them ) that might help you, just search for CPAP.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #7
    Re: Small RV for remote camping - inverter question

    And of course the lower humidity settings will be easier on your battery pack, as less electric heat would be needed to vaporize the water.
    Still find it hard to believe that (200 watt hours / 7 hours use) the blower and electrically heated vaporizer together, use less than 30 watts. Must be a very efficient unit.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Small RV for remote camping - inverter question
    westbranch wrote: »
    just remembered that there are several other CPAP threads ( 28 of them ) that might help you, just search for CPAP.

    And because the forum's search mechanism doesn't work well with short terms like "CPAP":

    https://www.google.com/search?q=cpap+site%3Awind-sun.com
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