Off-grid in a Caravan

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Off-grid in a Caravan

Postby beaujewel » Tue Nov 11, 2014 10:31 am

Hiya folks, longtime lurker with some questions.

We live fulltime in a caravan and id like to go off grid with it. Ive been calculating our power consumption and it breaksdown as follows,
Aircon 8 -10 hours a day (3 MONTHS A YEAR ONLY) @ 900 w/hr = 9000W
Fridge 8 hours a day @ 325 w/hr = 2600w
Jug 10 mins a day @ 1200 w = 200w
Iron as above 200w
Toaster as above 200w
Tv 6 hrs a day @ 150w = 900w

Thats a basic estimation, im in the process of cinfirming it with a power meter.
From my calculations I can get away with a 600ah lifep04 bank and 600watts of panels for a one day reserve.
When it comes to the inverter im not sure on sizing, would a powerjack 5000w unit do the job?
I think Im capable enough of modifying one to reduce standby consumption.
Any help.is appreciated.
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Re: Powerstar W7 Inverter modification

Postby Gordon-Loomberah » Tue Nov 11, 2014 11:11 am

You will need a LOT more PV panels than 600W. What voltage are you thinking of for your 600AH Lithium battery?

Also, regarding terminology, units of energy are Wh or kWh, whereas power, or rate of usage, is given in W or kW. w/hr is meaningless in this context.

10 hours at 900W is 9kWh
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Re: Powerstar W7 Inverter modification

Postby beaujewel » Tue Nov 11, 2014 11:18 am

Ok so by my calcs that is 4.1 kWh per day. Voltage for the batteries im not sure. 12v would be good as there are some 12v outlets that I qould like to continue using.
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Re: Powerstar W7 Inverter modification

Postby Gordon-Loomberah » Tue Nov 11, 2014 1:43 pm

Energy use calculations you posted above are over 13kWh/day. Depending on your location, 600W of panels will average (annually) from under 2kWh in southern regions to about 3.5kW per day in ideal desert locations- which is a big shortfall on your demand. You also need to account for inverter, charge controller and battery inefficiencies. I'd say you would require 4-5kW of PV at a minimum (location dependent), if you dont want to be running the generator a lot. Also, 600AH @12V wont be enough, without extensive use of the generator in extended cloudy periods of weather. I'd suggest 600AH @48V would be more like what you need, and use a 48VDCto12VDC converter for your 12V loads.
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Re: Powerstar W7 Inverter modification

Postby beaujewel » Tue Nov 11, 2014 2:49 pm

Ok, got a power meter and things look a little different. With the Aircon on low, fridge running and nothing else it is indicating 500 to 600w. Assuming that they are run for 10hrs ( overestimation) per day thats 5.5kwh correct?
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Re: Powerstar W7 Inverter modification

Postby Gordon-Loomberah » Tue Nov 11, 2014 3:54 pm

Yes 550W for 10 hours is 5.5kWh, but you need to be producing significantly more than that from your PV panels if you want to operate without much generator use.

Have a look at this thread for a bit more info:
solar-wind-gear/topic5108.html
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