dry camping

[Travis Martin]

Great explanation of the amp hour figure, Pete. Your refrigerator
shouldn't use that much juice though. If you can keep the door shut
most of the time, it should run about 30% of the time. The duty cycle
goes up a lot if you're fanning the door. Also, the defrost heater
uses a lot of juice when it cycles. It will normally occur once or
twice a day and last for about 12 or 15 minutes. Then the
refrigeration system has to run longer to cool things back off. You
can improve things a lot with a domestic refrigerator by keeping the
condenser coils clean and keeping the doors shut as much as possible.
Also, if there is a switch on its control panel for "humidity
control" or some such, you might want to keep it in the off or normal
or whatever it's labeled position. This is for some electrical
heating elements that are in the mullions around the door openings to
keep them from sweating in high humidity areas. The humidity probably
doesn't get that high inside your coach anyway. They use a fair
amount of electricity 24/7 when turned on. Not a big issue on shore
power, but could be significant when dry camping. A lot of the newer
refrigerators solve the sweating issue by routing the hot gas piping
from the compressor through the mullions before going to the
condenser; that's why you'll notice the mullions feeling hot to the
touch.

I'd like to see what the actual running amp draw is on one of these.
I work on appliances for a living; maybe I can remember to put an
Amprobe on one and see. I have a digital data logger that I can leave
in a refrigerator for a couple of days and tell you exactly how long
it's running and when it defrosts. Guess I need to find out how much
current it's drawing. Never been an issue in a home, but would be
good to know for when running on batteries.

Travis, the Newell guy in Lubbock, Texas


On Dec 2, 2007, at 7:58 PM, Pete Masterson wrote:

> The primary drain (through the inverters) is the power to the
> refrigerator. It will limit your ability to operate off the grid with
> an all-electric coach. (My '95 is all electric.) Newer refrigerators
> are perhaps a bit more economical to operate than the 22 cu ft 2-door
> Amana that I have in my coach -- but you're likely to experience the
> similar power drain.
>
> For example, I have 6 model 4D AGM-type house batteries. These have
> about 220 amp hours each. So, 6 x 220 = 1320 amp hours. However,
> that's an overstatement of what's available, as you can't deplete the
> battery more than 50% for standard wet cell or by more than 60% for
> AGM batteries. So that would mean there's between 660 and 792 amp
> hours available from the battery to power all the 120 volt systems
> that are serviced by the inverters. (I have two, 2500 watt
> inverters.) Also, don't forget that the inverters cause a loss (10%
> or more) while changing the 12 vdc to 120 vac. Don't forget that amps
> X volts = watts. So, a 1000 watt refrigerator is about 8.3 amps at
> 120 v per hour. Convert that to 12 vdc, and its about 83 amps. With
> the inverter loss, that's about 95 or 100 amps (per hour while the
> refrigerator is running)... so that suggests about 6 to 8 hours or
> perhaps 10 hours of operation (since it doesn't run 100% of the time)
> just for the refrigerator. Add the microwave (high draw, but short
> period) plus the various lights and the 12 volt stuff... and then you
> can see that the batteries are kind of limiting!
>
> Here's where you have to do some math. First figure out the
> approximate hourly draw in amps of each appliance that runs on 120
> volts. Don't forget that _some_ of the lights run on 120 volts and
> are powered by the inverters. Of course, all 12 volt items and
> appliances also draw from the batteries. So, you also have to figure
> out what 12 volt appliances you have operating. Do not ignore the
> draw from the Microphor toilet compressor nor from the air-system
> auxiliary compressor, if you have one (I don't) along with various
> signal lights, etc. etc. -- well, to be honest, there's a _lot_ of
> load on a 'bird and without a source to recharge, the batteries can
> be drawn down to a dangerous level in just a few days, even when
> everything is "off."
>
> So, back to the refrigerator -- the practical situation is to make
> sure your house batteries are fully charged. If you have an isolation
> switch to "turn off" everything, it would help. Anyway, when you
> think your batteries are fully charged, isolate them (and unplug
> shore power), then check the voltage. (This is the "resting"
> voltage.) For AGM batteries, it should be about 12.9 to 13.0 volts
> (wet cell batteries are different). Then, turn on the isolation
> switch (apply the normal load) -- wait and hour, remove the load, and
> check the voltage. 12.4 volts is 50% depletion and 12.25 volts is 60%
> depletion -- do not let the volts drop below 12.25 volts!!! ---this
> is "resting" voltage measured from the battery terminals.
> Measurements drawn from other locations (e.g. a fuse panel) are
> likely to be much lower due to line losses.)
>
> My experience has been that "boondocking" isn't especially practical.
> I can shut down the generator in the evening, but I usually need to
> restart after about 12 hours or so. So, if I shut down at 8:00 PM,
> I'll usually need to start the generator by about 8:00 AM the next
> morning to avoid causing any damage to my batteries. This has caused
> a fair amount of heart burn when I've stayed in a CA state park that
> had a generator operation ban between 8 PM and 10 AM ... those two
> hours were nail biting time and I had to shut down any/all items that
> made demands on the batteries.
>
> My plan (the next time I boondock) is to pull the breakers on the
> inverters perhaps at 10 PM or so, and see how the batteries are the
> next morning. The refrigerator won't warm up much during the night,
> if it is not opened and if we're in a reasonably cool location.
>
> I've compared notes with another all-electric Blue Bird owner (just
> this past weekend at the Lone Star Birds rally in Kerrville, TX) and
> I'm of the impression that my voltage drain seems to be on the high
> side (so I may need to further explore possible reasons).
>
> The reality is that you can probably turn off the generator in the
> evening then turn it back on in the morning without major problems.
> You can run the generator for 3 hours or so to bring the batteries
> back up to full or near full charge. Then you can shut down the
> generator for a few hours, then run it for 3 or 4 hours until the
> time you wish complete quiet at night (or until any required shut
> down time occurs).
>
> The coach can be off the grid without the generator for periods of
> several hours -- but it will need to have power to recover the
> batteries rather more often and/or for longer periods than coaches
> that have LP gas appliances.
>
> See Poop Sheets by Phred at:
> <http://www.phrannie.org/phredex.html>
> #5 has a thorough discussion of "electrical stuff."
>
> Pete Masterson
> '95 Blue Bird Wanderlodge WBDA 42
> aeonix1@...
> On the road at Lubbock Texas following a great weekend with the Lone
> Star Birds at Kerrville, TX.
>
> On Dec 1, 2007, at 2:08 PM, medpro28 wrote:
>
> > Just purchased a 2005 LXi and need some advice on dry camping. I
> cook
> > in bbq contests and sometimes no power or 110 only. Dealer says I
> > will
> > have to use the generator all the time. Although the unit is all
> > electric, will not use the stove top or microwave while camping.
> > It is
> > hard to believe I can't dry camp any length of time and then use
> > generator to keep batteries up.
> > Is the dealers advice right or does anyone have thoughts or
> > suggestions?
> >
> > Jerry Smith
> > 2005 450 LXI
>
>
>



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