How much solar do I need?

[marc71]

I’m posting for a friend. Let’s say you have 6-6 volt golf cart batteries and looking for enough solar power to keep the basics in a 32’ trailer going through the winter months. The camper is being used as temporary living space for hunting and the building of a cabin. Lights, heater, fridge water pump will be used, not much in the way of electronics or microwave. They’re trying to keep from having to winterize during off times so the biggest thing is to keep the heat on during down times. Is there a particular kit or package you would recommend?

Thanks you

[DrewE]

2oldman wrote:

theoldwizard1 wrote:
It is heated by a wood stove so there is no furnace.

I wouldn't want to brave an ID winter with just that for heat.

I grew up in Vermont in a house with a wood stove for heat. ID winters are probably a wee bit more severe than VT winters, but it seems close enough to me. We did have electric heat in the house that we never used (for all practical purposes, at least). It is a comparatively large amount of work, what with stacking and fetching in the wood, and not very amenable to being left on its own for a week's vacation, but otherwise about as reliable as any heat source. It didn't seem to me like there was much bravery involved.

I was the youngest of the children, and a year before I headed off to college, my mom realized that when I was gone she would have to haul in all the wood, and got an oil fired hot water heating plant installed. (Also factoring into that decision was the fact that the stove was getting pretty well worn out and would have needed replacement before too long.)

[2oldman]

theoldwizard1 wrote:
It is heated by a wood stove so there is no furnace.

I wouldn't want to brave an ID winter with just that for heat.

[pianotuna]

eight batteries 6 volt is not much storage. I had more than that in my RV.

[theoldwizard1]

I just watched a video showing a family of 5 living in a modern house, off grid, in ID. It is heated by a wood stove so there is no furnace. Water is gravity feed from a tank up the hill. No heavy electrical load except for the washer and LP gas dryer. Their battery bank is EIGHT 6V golf cart batteries.
With 3 MASSIVE solar arrays, a 3 day early winter storm left them running off of their old 3000W generator.

[pianotuna]

2oldman,

Good point. I did originally design the battery bank to allow me to run a block heater for 3 hours on the battery bank at -40.

[2oldman]

pianotuna wrote:
That number does not allow for cloudy days or snow covered panels.

..or cold batteries..?

[pianotuna]

assuming 50% duty cycle and 20 amps draw on the furnace fan @ 12 volts 800 watts of solar would be enough.

However it is going to require a LARGE battery bank of about 6000 watt hours (~500 amp-hours). That number does not allow for cloudy days or snow covered panels.

If you wanted 3 days of redundancy then aim for 1500 amp-hours of battery bank.

[time2roll]

Could need a 100# propane cylinder (or 2) if you expect to burn propane a few days unattended.
Not sure an RV thermostat goes under 50 or 55 degrees.
Batteries can freeze if they become discharged. Especially over 50%.

[2oldman]

marc71 wrote:
(like keeping the t-stat on 35-45) and having enough battery reserve to keep the fan running .

If that's even possible to go that low.

Were I in this situation I'd plan on winterizing it instead of relying on heat. I'd be worried the entire time relying on battery heat.

[marc71]

They plan to be on the grid at some point, there’s 4/10 of a mile through neighboring property to deal with and I’m not up and all those details. There will be a generator involved in the set up and the solar panels will not be mounted on the roof of the camper, some type of stand to keep them off the ground. The biggest issue is going to be when the camper is not occupied in below freezing temps to keep anything from freezing (like keeping the t-stat on 35-45) and having enough battery reserve to keep the fan running for what could be a couple of days between visits to the property. Obviously outside temps will play a factor in any situation, just looking for ideas on how much solar will be best, there’s room for a few more batteries as they aren’t mounted on the trailer but in a box right next to it.

[Lwiddis]

You and your friend need to do some reading on solar. Start with an energy potential use survey. That will determine necessary battery amps. Then...

[time2roll]

Winter is tough on solar due to low angle and clouds. Cannot say an exact number any more than you can predict the weather. Best shot will be to supplement charging to reduce generator run time.

For travelling I would typically recommend to mount flat on the roof. However for winter in a fixed location a ground set up tilted to the sun is probably best. If you are in a shaded valley or in a bunch of trees it may not even be worth the effort and cost.

Otherwise I recommend 300 to 800 watts and a small 2000w generator. +1 to just start with a utility drop and focus on the project.

[ppine]

Maybe 300-400 watts with a generator for back up would be in the ball park.

[wanderingaimles]

Typing on a phone at Dr office, duplicate