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Old 12-19-2009, 06:58 PM   #1
rvan
 
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Default All electric camper

Newbie here with some electrical questions:

Planning a camper conversion that will be used for camping and road trips.
Like to keep things real simple: No AC, no refrig, no generator, no TV, Furnace, no DHW.

Like the concept of all electric but do not know if it will work.

Electric: 250+AH Battery with 1500w inverter.

12V: Lights (Minimal), Water Pump, Charge: Cell & Camera, Computer(DVD), I-Pod and Fans

1500w Inverter: Induction cooktop (one burner), 660w microwave, hairdryer and electric blanket (10 minute preheat only).

Questions: Can I use computer with 12V only?
Is inverter switched on and off? If no load is it automatically off?
Is it correct that I could only run one 110V item at a time?
Which is more efficient, 12v or 110V electric blanket?
Will 1500w inverter run microwave or induction cooktop?
Do roof mounted solar panels hurt gas mileage?


Thanks,
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Old 12-19-2009, 07:37 PM   #2
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Default Re: All electric camper

Quote:
Originally Posted by rvan View Post
Newbie here with some electrical questions:

Planning a camper conversion that will be used for camping and road trips.
Like to keep things real simple: No AC, no refrig, no generator, no TV, Furnace, no DHW.

Like the concept of all electric but do not know if it will work.

Electric: 250+AH Battery with 1500w inverter.

12V: Lights (Minimal), Water Pump, Charge: Cell & Camera, Computer(DVD), I-Pod and Fans

1500w Inverter: Induction cooktop (one burner), 660w microwave, hairdryer and electric blanket (10 minute preheat only).

Questions: Can I use computer with 12V only?
Is inverter switched on and off? If no load is it automatically off?
Is it correct that I could only run one 110V item at a time?
Which is more efficient, 12v or 110V electric blanket?
Will 1500w inverter run microwave or induction cooktop?
Do roof mounted solar panels hurt gas mileage?


Thanks,
I can't answer all your questions, but i can try for a few.

I personally have tried to run everything off 12V. That means no microwave or other heavy electric heating devices. A typical hair dryer, for instance uses at least 1500 watts and would max out the inverter you have chosen, as well as run the battery dead in very short order. Same could be said for the electric blanket, depending on the current draw. You need to look at how many amps or watts each device draws, and calculate how many amp hours it will take to run those appliances. Never run your battery below 50%, so a 250 AH battery is good for 125AH.

What kind of computer is it? Most have 12V adapters available, i have even found one for the Macbook Pro now.

A solar panel on the roof has very little drag because it's usually mounted so close to the roof. The gain from the power source makes up for the small drag it produces, IMHO.

I do have some 110V heating and cooking devices on board, but only use them when plugged into shore power. We do have a refrigerator that runs off the battery which is charged by the solar panel. That would be my wife's favorite item, right after the diesel fueled stove/heater.
Hope this helps.
Jef
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Old 12-19-2009, 08:36 PM   #3
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Default Re: All electric camper

Quote:
Originally Posted by rvan View Post
Newbie here with some electrical questions:

Planning a camper conversion that will be used for camping and road trips.
Like to keep things real simple: No AC, no refrig, no generator, no TV, Furnace, no DHW.

Like the concept of all electric but do not know if it will work.

Electric: 250+AH Battery with 1500w inverter.

12V: Lights (Minimal), Water Pump, Charge: Cell & Camera, Computer(DVD), I-Pod and Fans

1500w Inverter: Induction cooktop (one burner), 660w microwave, hairdryer and electric blanket (10 minute preheat only).

Questions: Can I use computer with 12V only?
Is inverter switched on and off? If no load is it automatically off?
Is it correct that I could only run one 110V item at a time?
Which is more efficient, 12v or 110V electric blanket?
Will 1500w inverter run microwave or induction cooktop?
Do roof mounted solar panels hurt gas mileage?


Thanks,
Welcome rvan, this site will answer many of your questions...

http://www.ccis.com/home/mnemeth/12volt/12volt.htm
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Old 12-19-2009, 09:04 PM   #4
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Default Re: All electric camper

We have never installed solar panels but have checked out others hoping to add them at a future date. Some things to consider: (1) Allow your panels to tilt for the low angle of the winter sun. (2) Be able to take off your panels to position them on the ground when you are parked in the shade. Versatility is good. In the summer you may not want to park you van in the sun. Don't attache your panels permanently as the may not last forever. Good luck.
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Old 12-19-2009, 09:46 PM   #5
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Default Re: All electric camper

Quote:
Originally Posted by rvan View Post
Newbie here with some electrical questions:

Planning a camper conversion that will be used for camping and road trips.
Like to keep things real simple: No AC, no refrig, no generator, no TV, Furnace, no DHW.

Like the concept of all electric but do not know if it will work.

Electric: 250+AH Battery with 1500w inverter.

12V: Lights (Minimal), Water Pump, Charge: Cell & Camera, Computer(DVD), I-Pod and Fans

1500w Inverter: Induction cooktop (one burner), 660w microwave, hairdryer and electric blanket (10 minute preheat only).

Questions: Can I use computer with 12V only?
Is inverter switched on and off? If no load is it automatically off?
Is it correct that I could only run one 110V item at a time?
Which is more efficient, 12v or 110V electric blanket?
Will 1500w inverter run microwave or induction cooktop?
Do roof mounted solar panels hurt gas mileage?

Thanks,
A 1500w inverter is probably sufficient as long as it is pure sine wave. A msw inverter might cause microwave and (ac version) electric blanket problems. Your computer/dvd and rechargers are likely 50w or less and not too important if you don't run them more than a couple of hours.

Even very efficient inverters consume some power at idle---an easy-to-use power switch location is strongly recommended.

I've got the 2000w Prosine and that gives me some useful extra-devices margin when I run my 1100w-input 650w-output microwave or the up-to-1200w induction burner. (I see that Sunpentown offers a 1500w version as well as my 1200w version. Pretty happy with mine, toss-up about buying the 1500w if done again.)

Your 250ah bank is a little undersized for the 1500w draw of a hairdryer or other big draw. You might get a little voltage drop. Xantrex is conservative but I followed their recommendation of 400ah+ for my 2000w Prosine 2.0. You do not want to be at the minimum since batteries degrade eventually. And more ah means more flexible camp use.

And note that a 24hr, low-watt draw like a portable Engel fridge matches up well with the big bank you need for a few minutes of high-watt appliances. A nice future upgrade option for you.

We don't use an electric blanket but a lot of campers prefer a more efficient heating pad underneath. We use the furnace at night here and there since a good down comforter works so well.

Advice about heat: our Airtronic D2 diesel furnace is very, very satisfying. Electrically efficient. sips diesel, eliminates installed propane for us. The use at night is nice but not strictly necessary. It is the daytime use where it is really appreciated. My wife happily works on the laptop for hours while I'm paddling whitewater. It is a very different camping experience to not be cold if you need to spend time inside.

And the second-favorite item is the Fantastic Fan when it's a bit too warm.

My take on rooftop solar: A car loses around 5-7% mpg at highway speed with a roofrack bars installed. And mpg also go down for a car at about the rate of 1 mpg for every extra 250lbs. So a solar panel probably costs in the ballpark of 250 gal of diesel over 100k miles of highspeed driving. Solar is very nice if you sit still in camp a lot and park in the sun most of the time. I'm mostly a shade camper, recharge with alternator miles frequently, drive fast mostly, and carry boats on my roof. I think extra batteries are more cost-efficient for my use.

Panels cost $5/watt when I did my conversion. About half that now with a good deal. I'll add a panel when the cost makes it to $1/watt in two years.

Dan
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Old 12-19-2009, 10:27 PM   #6
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Default Re: All electric camper

Thanks Dan for your comments. My wife and I use our 2008 Sprinter also for camping, traveling and some hauling. We did purchase an Engle portable refrigerator (I think 45 quart) and it fits between the front seats and plugs into the cigarette lighter (power outlet). Ours came with the dual batteries which is nice and I have not even noticed a change in auxiliary battery power when camped for up to two days. The engle is very efficient and very quiet and works even when not level. The take out basket is nice when we get home and want to clean out and put things in the house refrigerator. I second your opinion on the fantastic fan, they are fantastic. I will be checking into the Airtronic D2 diesel furnace. Dave
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Old 12-19-2009, 10:49 PM   #7
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Default Re: All electric camper

Hi rvan,

1. HP produce a 12v to 15 thro to 19v selectable power adapter for your laptop computer. This is the preferred method as if you use a 1500w inverter, it would be very inefficient use of your battery capacity.
2. Depends on inverter manufacturer, however it will still draw a small amount of standing current if it is not switched off.
3. Depends on the size of inverter and battery, but with a 1500w inverter generally you would only be able to run one heavy current appliance at a time.
4. Electric blankets are 100% efficient whether 110v or 12v. The issue comes down to other losses in the distribution system of getting power to the blanket. If you use the inverter to run your 110V electric blanket, typically 100w or less load, then there are considerable losses in running the inverter. Much better to run the electric blanket off 12v.
5. Lights.. use LED lights, the current drain on these for the same light output as an incandescent light is 10% and 20% lower than a fluorescent lamp.
Water pump uses about 3 amps when running. As you normally are not running the pump for more than a few seconds at a time, the pump is not a signficant user of battery energy.
6. Charging small appliances... use a small inverter, say 60 to 100watts for these as it is most inefficient to use a 1500w inverter for this use. Run fans off 12v.
7. Inverter to run microwave and induction hob. Inverters are rated for a completely resistive load. some do have a short term rating which is higher than the continuous rating. Microwaves and inductive hobs have very high inrush currents. This requires an inverter rated at least 1.5 to 2 times larger than the appliance rating.
8. Roof mounted solar panels may affect fuel consumption but not very significantly... say 1%. Compare the area of the front of the vehicle to the forward face of the solar panel!! Ches makes good valid points, but it depends on where you are travelling to. If you are not going above about 40 degrees North then mounting solar panels permanently horizontal is OK. Allow for about 10% increase in size to correct for the area loss due to not facing directly to the sun. Do you want to constantly be moving the panel to get maximum charge?!!! If you mount the panel on the roof then ensure that it is spaced about 1 inch above the roof to allow airflow under it, as solar panels lose their conversion efficiency when hot.

My advise on the high power devices is dont fit them. Cedarsanctum has made very valid points here.

Batteries and charging... A conventional liquid lead acid deep cycle battery can only be charged to about 75 to 80% from the engine alternator or solar panel with a conventional regulator. As Cedarsanctum says, they should not be discharged below 50%. That means that your battery only has a useful energy storage of 25 to 30% !!! This is why so many installations fail early. To fix this problem, use an agm or gel battery and a solar regulator which has MPPT capability. (Maximum power point transfer) see http://en.wikipedia.org/wiki/Maximum..._point_tracker

This will charge a gel battery to 100% and the gel battery can be discharged to 30% giving you a useful capacity of 70%!!

Also use a single 12v battery with the capacity required instead of two or more batteries in parrellel. Batteries in parrellel will not fully charge equally as the internal resistance of each battery may be different. particularly over time. Batteries in series are OK as the same amount of current will flow through both. ie 2 x 6v. However they tend to be dearer than a single battey of the same total Amphour capacity.

One last point. Wiring... Ensure that the wire size to each appliance is adequate for the job. Use the rule of thumb that the voltage drop from the battery to the appliance when running should not exceed 3%. At 12v this equates to 0.36Volts.

Whew!!! I think that is enough for today.
Hope this helps
Cheers Ross
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Old 12-20-2009, 03:05 AM   #8
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Default Re: All electric camper

Re electric blanket. I burned out two electric blanket controllers on boats that had modified sine wave inverters. Definitely use a true sine wave inverter.
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Old 12-20-2009, 04:43 AM   #9
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Default Re: All electric camper

Also re electric blanket: An underpad is far more efficient and far nicer to sleep with than an overtop electric blanket. I run mine at full for about ten minutes before bed, then turn it off.
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Old 12-20-2009, 08:55 PM   #10
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Post Re: All electric camper

Thanks for all the helpful responses!

The hairdryer, microwave and electric blanket were just bribes to get my girlfriend out of a hotel.
Also I figured about 10-20% of the time I would have access to 110V.
As a builder who does super efficent homes we have had good luck with all electric homes (with PV solar).

So it seems there are two directions I could go:

1) Stay all electric and upgrade battery (gel) and inverter.
Minimize use of hairdryer and use 12v heating pad instead of 110v electric blanket.
Run computer off 12v. Accept one appliance at a time (no problem).

2) Save a fortune on batteries & inverters and go with a propane cookstove, drop the hairdryer and microwave.
Have 10 lb propane tank and cooktop for outside use but did not like using it inside, which is the reason for induction cooktop.
Would really only use it inside for coffee or soup, most cooking would be outside.

Will think about the diesel heater as a future option (any way it could be a hairdryer???).

Thanks again

Last edited by rvan; 12-21-2009 at 05:30 PM.
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