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PodRacr View Drop Down
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Direct Link To This Post Topic: Inverter installation
    Posted: 31 Dec 2012 at 2:57pm
I am looking to make a project of this for spring before we start camping.   I wanted to bounce this off the more electrically savvy members here and make sure I don't  make any inaccurate assumptions or costly mistakes.

We bought ourselves a generator Honda E2000ui and a Electric coffee pot for Christmas as we dry campy 95% of the time. My wife was getting fed up with not being able to make a decent cup of joe with our camp percolator.  I know this generator is not capable of reliably getting the 13,500btu AC to start if it was needed, but has more than enough juice to run it once its past the surge point and going.

We have the R-pod 171 and my thought was to install a 1600 or 2000 watt inverter, the ones I am looking at supports a 3000/4000 watt surge load for up to 10 seconds which should be enough to get the AC to kick on and running in its normal sub 1600/2000 watt range.  However this inverter is a Modified Sine Wave inverter which does not play nice with fancy electronics such as microwaves, laptops, etc.  The camper is setup with two 220AH 6v batteries so I should have 440AH @ 12v.  The generators DC clamps would be used to keep the batteries topped off while the AC was running so the batteries are not run down.

I could get a Pure Sine Wave inverter, but this may triple the cost of the inverter, and the only bonus is the ability to power the microwave and laptops and such.

So here is the question.  My camper is down in storage so I cannot look or measure.   What gauge of wires are used by Forest River to bring in power from the batteries down to the converter?  Can I connect to those existing lines?  If they are 0 guage then I can tie the inverter directly to the same wiring.  Those would be helpful so I would not have to buy/install new 0 gauge battery lines.  I am planning on a 180 or 200AMP breaker as it appears to be the limit the inverter can handle is 200A.

Has anyone else done an inverter to power the air conditioner?
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techntrek View Drop Down
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Direct Link To This Post Posted: 31 Dec 2012 at 3:33pm
Welcome.
 
Actually modern electronics are designed to accept a lot of junk - including modified sine wave - by design.  Very few things may have problems, usually things with built-in chargers like rechargable shavers and odd things like X10 controllers.  Computers, modern televisions, etc, are all ok on modified sine wave since their internal power supplies convert it to DC anyway.  Microwaves are a special case and operate more like motors in that they need to run about 30% longer to do the same heating on modified sine wave, but they do work.
 
The built-in chargers in generators are very poor chargers and won't keep your batteries topped off while running the A/C.  They are barely trickle chargers.  You would need to use a high-capacity charger operating from the 120 volt output from the generator.  That said, a 1300 watt-hour load @ 120 volts equals well over 108 amp-hour at 12 volts and no charger can support that.  You would need even more than 108 amps after the losses from converting from AC to DC then DC to AC, and taking into account starting surges over time.  Most consumer chargers will only output 50 amp-hour max and then only do it for a short time to help start a car.  They usually will only output 20 amp-hour continuous.
 
Motors use up to 30% more energy while running from modified sine wave.  My A/C uses about 1000 watt-hour with the internal fan on low (on pure sine wave), which would be about 1300 watt-hour on modified sine wave (this is the figure I used in the last paragraph).
 
As you increase your battery's output voltage by hooking them up in series, amperage stays the same.  So you have 220 amps (not amp-hour) @ 12 volts.  If you had hooked them up in parallel you would have 440 amps @ 6 volts.  Either way your total power is the same, amps times volts which in both cases is 2640 watts.  However, most of the time lead acid batteries should not be taken below 50% state of discharge so that leaves you with 110 amps available - or about 1320 watts IF you discharge them at a 20-hour rate (about 65 watts per hour for 20 hours).  The quicker you discharge a lead acid battery the fewer total amps are available.  Look up Peukert Effect for details on that.
 
So bottom line, it isn't going to work.  I see where you were going with the idea but there are a lot of details which won't make it feasible.
 
I have considered installing a special type of A/C which uses a lot less energy (about 300 watt-hour) but even that would require six 110 amp 12 volt batteries to run it two nights for 8 hours each night.  The standard RV A/C just can't be run from an inverter for very long unless you take thousands of pounds of batteries.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Direct Link To This Post Posted: 31 Dec 2012 at 3:47pm
See that's why I ask first, I am not and engineer.  LOL Well dang.   Scratch that idea.   Would it still be feasible for the coffee pot and microwave?   I try not to run the generator in the morning when I camp to be respectful of other campers that might be nearby.  I have not bought the load tester yet to see its exact load but I expect 1300-1500 watts for the coffee pot.  The coffee pot and the microwave should be used for shorter durations.

Still sounds like a Pure Sine Wave inverter might be the way to go.




Slightly off topic -
Are there better electrical converters/breaker units that incorporate better chargers that one might use to replace the factory one?
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Direct Link To This Post Posted: 31 Dec 2012 at 4:10pm
Have you considered a French Press?  Needs no electricity, just add hot water and makes a superior cup of coffee.  I purchased an electric coffee bean grinder at Costco for about $26.  Grind the beans right before making coffee and you will wonder why you have been using a percolator, all these years.  Safe Travels.
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Direct Link To This Post Posted: 31 Dec 2012 at 4:51pm
We only dry camp, therefore I bought the honda EU2000i . I'm very happy with it, it is quiet and light.
In the morning we run it to make toast and cafe, in the evening to heat up our dinner in the microwave, while doing that it also tops up the batteries. The gen. also runs the AC (11000 PTU) I probably will never use it because I live north of the 49th. My gen. is build in, in a container at the back of the trailer. By insulating the container and diverting the exhaust to the ground, I cut the noise level by another 50%.
To elimenate the vibration in the trailer I put a bottle jack under the gen. and lifted it about 1/4" to 1/2"
to make it self supporting, the vibration is almost zero. I dont think the noise of the gen. is any worse then screeming kids, barking dogs, blaring musik or somebody chopping fire wood.
If you want something done right, do it yourself.
2011 RP172, 2016 Tundra 5.7 Litre, Ltd.


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Direct Link To This Post Posted: 31 Dec 2012 at 5:17pm
I recommend getting a Kill-A-Watt to test your loads.  Once you test your coffee pot you can go around the house and figure out what else uses more energy than you think.  One case in point, satellite and cable boxes (non-DVR).  I found mine use about 30 watt-hour.  Not a big deal, until you multiply that by 24 hours, then by 30 days.... 21,600 watts every month, 259,200 every year.  Now all of my non-DVR satellite boxes are on switched outlets.  They boot up and get the immediate TV schedule within a minute.  Obviously I don't turn off the DVRs.  I'm still waiting for the manufacturers to wake up and start making models which go to sleep when they aren't recording or being watched... mine uses about 40 watt-hour 24/7.  Ouch.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Direct Link To This Post Posted: 31 Dec 2012 at 6:58pm
I will have my wife look into the french press.   I used to install directv, had no idea they pulled that much power.  very interesting.
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Direct Link To This Post Posted: 01 Jan 2013 at 10:34pm
I installed a 800 watt modified sinewave inverter in my trailer but I only use it for operating a cpap machine. The cpap will run one battery down in 8 hours so you would need a lot of batteries to run a.c. For any length of time. Techntrek is right most modern electronics will work fine with modified sine wave.
Sean, 2011 Rpod RP-173,2009 Jeep Liberty Rocky Mountain Edition
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Direct Link To This Post Posted: 02 Jan 2013 at 11:15am
With that French Press, do purchase a burr grinder with it.  Not the cheapo high speed grinder.  Supposedly for the afficionados it gets the beans too warm while whirring at high speed.  You could also find a larger pepper grinder for manually grinding your beans.  If you buy whole beans and grind right before brewing, you will get a terrific cup of coffee.  Since you haven't posted where you live, can't give you any suggestions on where to find a cup of French pressed coffee.  Check the better coffee houses near you.  You won't be disappointed.  Safe Travels.
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