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Old 07-03-2012, 08:48 AM   #1
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What size power inverter?

I'm going to buy a small power inverter. I want to connect it directly to the battery on my JKU and run an extension cord to my tent in the woods. I want to connect a household fan to it... one of those $15 box fans or possibly a small oscillating fan to circulate the air in the tent at night.

What size power inverter do I need just to run a fan? I won't have anything else hooked to it at the same time.

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Old 07-03-2012, 08:53 AM   #2
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a small one should work, just look at the amp rating of the fan and use this forumla

P = IV P-wattage, I-current, V-voltage

P = (5)120 (using 5amps as a example)

P = 600 watts

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Old 07-03-2012, 08:55 AM   #3
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I have a small one to plug in my cigarette lighter but never paid attention to what it'd run. Got it for my tablet which has a gps/trail map on it.
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Old 07-03-2012, 09:55 AM   #4
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Problem is, NONE of the fans at Walmart have info. on the box showing how much power they consume. So I'm having to guess.
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Old 07-10-2012, 04:24 PM   #5
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Quote:
Originally Posted by WXman View Post
Problem is, NONE of the fans at Walmart have info. on the box showing how much power they consume. So I'm having to guess.
Just Open the Box and Find the Power Sticker / Tag on the Fan. If someone Asks what you're doing, just say you need to know how much Power it Uses.

I would Think you'd be Fine with a 600w Inverter though.
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Old 07-10-2012, 08:47 PM   #6
Knows a couple things...

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You'll be MUCH MUCH better off by buying a 12v fan from somewhere like a truck stop or trucker's supply.

Using an inverter to create 110vac would be highly inefficient, more expensive than just buying a 12vdc fan, and require more current from your battery.

Like nearly any of the 12v fans at
https://www.google.com/search?q=12v+...w=1280&bih=820
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Old 07-10-2012, 08:51 PM   #7
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I ended up buying a power converter from Walmart rated for 450 watts continuous load, 700 watts peak surge. It powered my household fan like a charm all weekend! And it never ran down my battery. I have a feeling I could run a few things off this converter and it will really be nice. Having the big household fan to move air around inside the tent was great... it was 102 degrees outside.
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Old 07-13-2012, 11:47 PM   #8
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That's exciting to hear because the only thing keeping us from camping is the fact that I have to use a CPAP machine and its not much larger than a clock radio. So this tells me I could get an inverter and just run an extension cord into the tent for it and the battery would be fine in the morning.
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Old 07-13-2012, 11:55 PM   #9
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Yup, try finding a 12V Cpap or Bipap lol
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Old 07-13-2013, 11:51 PM   #10
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Quote:
Originally Posted by Ibuildembig View Post
a small one should work, just look at the amp rating of the fan and use this forumla

P = IV P-wattage, I-current, V-voltage

P = (5)120 (using 5amps as a example)

P = 600 watts
That only works on DC circuits or purly resitive AC circuts

An occilatiing fan is going to be an inductive AC circuit. You will have to know the inductance of the fan motor to figure out power factor, as the current and voltage will nto be in phase...
Also, if the circuit is TOO inductive, some invertersts will not power them. You may have to add a resitive or capacitive load to the circuit.


Quote:
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Yup, try finding a 12V Cpap or Bipap lol

I have a 12V Cpap machine! Though I'd have to see how much current it pulls on the 12V line and make an adatpor for the cig lighter power port.

CAN these Jeep batteries power a CPAP all night for campin? That's the same thing that's stopping me from camping too. I guess there's only one way to find out...
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Old 07-13-2013, 11:56 PM   #11
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Get yourself one of those battery starter/chargers to hook it up too. I wouldn't chance killing the battery.
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Old 07-16-2013, 07:20 PM   #12
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As far as there being a TOO inductive load that an inverter will not power, that is because of the INRUSH current on inductive loads, not because of the pure inductiveness. Similar issues would occur if the load was too much of a CAPACITIVE load and NOT just because the load WAS capacitive. In the case of small loads (like almost anything you would put in a tent) P=IE is close enough for calculations.

if your inverter has a PEAK rating that is HIGHER than the inrush wattage, no issues.

Now..... the CPAP machine. One would suspect that this would NOT be an issue but, there could be. Medical equipment can be far more sensitive to power fluctuations than ordinary electronics (clock radios, microwaves, etc). I would consult with the manufacturer and see if they recommend. The restrictions on peak-peak or transient voltage could be much more restrictive.

AND.... before the electronic heretics put me on the cross...... all of this is still a function of the quality of the AC voltage coming out of your inverter. Cheap inverters should ONLY be used on non-sensitive loads like fans and microwaves and such.

ALSO.... inverters (like personal generators) have a FINITE amount of energy to be transferred. This means that you cannot just hook up ANYTHING you like and expect it to work. The PEAK wattage of your device MUST be less than the PEAK wattage of your inverter/generator.
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Old 07-16-2013, 11:58 PM   #13
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My cpap machine uses a power converter to convert 120vac to 12vdc. So I could just build my own adapter to plug straight into the DC power source on the Jeep.
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Old 07-17-2013, 06:23 PM   #14
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Cpap

Quote:
Originally Posted by insylem View Post
My cpap machine uses a power converter to convert 120vac to 12vdc. So I could just build my own adapter to plug straight into the DC power source on the Jeep.

Please make sure to consult the OEM or manual to determine what size fuse to put in there. Would not want it to catch fire or start melting due to excessive current issue.

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