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diy solar

Solar trailer as backup generator

alfaeric

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Jan 21, 2020
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I'm sure we are not alone in getting more events where our power goes out.

But it seems that it would be a good idea to use a camper trailer that would be set up for solar off grid power to also be used to supply some back up power to some appliances in your home. At least it does to me....

My thinking would require an extension cord from the trailer's 120v system into the home- but other than using the outdoor outlet for a fridge, would it be a good idea to make it more complex? When I finally make the step to go solar on the trailer, it will be pretty darned large, as we have electric only- no gas for anything. Which means the battery pack will be pretty darned large (still measuring use to know how much is needed).

Thoughts?
 
when starting down the solar path begin with writing down what you expect it to power...
That is really going to drive everything.
 
when starting down the solar path begin with writing down what you expect it to power...
That is really going to drive everything.
It would only need to run a handful of things for the home. For the camper- stove, microwave, AC/Heat, and coffee maker would be the big stuff. My surge protector tracks power usage, and this weekend, I'll start a spreadsheet of daily usage.
 
It would only need to run a handful of things for the home.

I, and I think almost everyone thinking of solar, say the EXACT same thing when starting out hehe

it is amazing how much power some "small" items can consume (I am looking right at you Mr. in-rush microwave oven!!)

if you can actually track your real power usage you are WELL ahead of most people when starting.
 
it is amazing how much power some "small" items can consume (I am looking right at you Mr. in-rush microwave oven!!)
We have a "smallish" 800W microwave oven.

Sharp Carousel Microwave Oven model R-230L(S)
Power supply: 230-240V 50Hz 5.2A
Input power rating: 1.22kW
Output power rating: 800W

Video shows actual power draw for whole of home (with baseline consumption of ~600W) when the microwave oven is turned on and off. Two short power on / off cycles at standard power setting are performed.

Actual power draw of the oven is 1.4kW.


Note: Video resolution will improve once Youtube finishes processing HD version.
 
Running an extension cord into the house is a valid idea. I’m also assuming your appliances will be plugged in directly to this cord and not the solar generator cord into a house outlet with the intent of feeding all outlets in the house. THat would backfired into the grid and bad for lineman.

If you don’t need Air Conditioning, I think a 10 kWh battery bank may provide what you need for a day, but there’s a lot of depends and it could be less and without some good discipline would easily be more.

When I hear a “No Gas” RV build, I think between 2 kw and 4 kw of panels. Actually, what I thought out still used gas for cooking, but would allow a couple of two to five minute showers a day. Electric cooking could drain a lot more.
 
Running an extension cord into the house is a valid idea. I’m also assuming your appliances will be plugged in directly to this cord and not the solar generator cord into a house outlet with the intent of feeding all outlets in the house. THat would backfired into the grid and bad for lineman.
I have a power inlet into which I can connect my backup power source, be it an off-grid solar/battery system or a generator (I have both). The power inlet is connected to a transfer switch in my home's main circuit board such that when the switch is flipped to backup, all of the circuits connected on the backup side of the switch are completely isolated from the grid.
 
Running an extension cord into the house is a valid idea. I’m also assuming your appliances will be plugged in directly to this cord and not the solar generator cord into a house outlet with the intent of feeding all outlets in the house. THat would backfired into the grid and bad for lineman.

If you don’t need Air Conditioning, I think a 10 kWh battery bank may provide what you need for a day, but there’s a lot of depends and it could be less and without some good discipline would easily be more.

When I hear a “No Gas” RV build, I think between 2 kw and 4 kw of panels. Actually, what I thought out still used gas for cooking, but would allow a couple of two to five minute showers a day. Electric cooking could drain a lot more.
Correct, I would just run an extension cord to the fridge. Other than that, maybe the cable modem, but that takes almost nothing.

we have already spent a few hours in our trailer when the power went out, 12v tv for the win. But to be able to keep the food safe would be nice.
 
I have seven 100 ah Battle Born batteries in my Arctic Fox 22G and 1440 watts of solar on the roof and additional portable panels. I installed a 10 circuit manual transfer rated at 30 amps at my house. I have my furnace, refrigeration, lighting, evaporative cooler, network/computers and other circuits that can be switched from utility power to the 30 amp input plug outside my house. I can use my Honda EU2200 to power stuff but I use my Victron Energy Multiplus from my trailer because it can surge to 6000VA for startup of motors and other short surges.

I have my trailer plugged into a 30 amp circuit from my house. I have the input to the transfer switch for the VE Multiplus in my trailer under relay control. I have a Cerbo GX that is connected to my Multiplus, BMV712 and my MPPT controllers. I have the Cerbo GX open the relay to the transfer switch when my batteries are above 73% and close the relay so power flows from the house when the batteries are below 70%. This allows me to power shift about $30 of electricity to my solar system instead of utility power. The other benefit is it acts as an 8.4 kilowatt UPS for critical circuits in my house. When the power goes out, I log into the website of my power provider and look at the estimate of power restoration. If it is a short estimate, I do nothing other other than watch the battery SOC. About 4 times in the last two years we had long power outages. I would take the time to fill my 5 gallon gas can and fire up my Honda generator after sun set to keep my important circuits going after dark. Once the power outage is over, I drain my generator and put the remaining gas back into one of our cars so we don't deal with stale gas.

Before the Cerbo GX I was manually flipping circuits on in the morning to the trailer and back to utility power at about 5 PM. The automated system works well and I am happy with it. I don't run all 10 circuits on the transfer switch from trailer power. I run about 6 of them on the trailer under normal conditions. For example, I don't need the furnace in the same season as the evaporative cooler.

I have a large solar power system on our trailer so I can enjoy the air conditioning in the daytime without a generator when we are away from hookups. I usually turn off the air conditioning by 7-9 PM because overhang temperature in the Great Basin don't require it. I have a Mach 1 Power Saver unit in my trailer that only needs about 9.3 amps.
 
I've been working on a solar trailer. The main idea is to use it for portable power and emergency home backups. It's not perfect, but it's a very inexpensive project, as I'm building it all from used and repurposed parts.
Right now, it weighs about 1400 lbs, and I can tow it with my Mitsubishi iMiEV or Chevy Volt. I should still be able to add an entire electric car battery to it for a significant storage upgrade. Right now, it just has a small battery built from 7 Nissan Leaf cell modules.
I have a whole YouTube video series going on how I'm building it.
Hope this gives folks some ideas!
Here's the playlist:

IMG_4844.jpg
 
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