How to measure how much solar we need?

[path1]

(hope this is right section) Brought home TT last month and now have basics taken care of and RV is road ready. Now starting to think about bigger long term projects.

One project is, we would like to get some solar. Which I know nothing about. I suspect the first step is figuring out a starting place for this project. So I'm assuming that finding how much we actually need might be a good starting spot.

Is there any meter or way to measure to figure out what we need? I'm thinking, if we know how much we use, we could determine how big or small of solar project would be. Thinking in my mind about some type of elec meter that we see how much we use in a week.

Or maybe better yet; how did you figure out how much solar you needed?

Anybody care to pass on any good links or info on RV solar?


Thanks

[bukzin]

Snowman9000 wrote:
Agree with Rjsfishin's first post. In earlier times, solar was very expensive, it made sense to do an audit and a lot of figuring. Now, you can install a pair of 100w 12v panels, mounts and hardware, 8 AWG wires, fuse or better yet an audio supply breaker you can trip for service, a cheap PWM controller (read and or ask here), some terminal ends for wiring, and a cheap meter, all for less than $400 DIY.

If down the road you feel the need to go big, the 8 AWG wire, breaker, and controller will be replaced. You'd be out say $50. IF.

That's my generic recommendation.

Which 'audio supply breaker' do you like.

Do you have any photos or suppliers links?

Thx!

[JiminDenver]

Now if someone comes up on us out in the middle of no where and sees a steam turbine on a wood stove, they are going to think we are moon shiners.

[reed_cundiff]

As noted above, we spent a week at Klahowya Campground near Forks/Beaver area on Olympic Pensinsula. Trees were 150' tall or so and we had no problems since we have a large bank of LFP. We did drive there and checked out the area before we drove the rig there and found a spot that would give us an hour of sunlight each day. Had Pacific Wrens coming to our feeder.

We spent a week at Stewart CG in the Chirichuahas which had about zero sunlight but we were only down -5500 W-hr (65% DOD). We had Painted Redstarts and Blue-throated Hummingbirds coming around all day long

We spent a week in the jungle at the north end of Lago Bacalar in the Yucatan and did well. There was enough dispersed sun to keep the batteries (glass mat then) up and we pretty much kept the inverter turned off. Toucans, Aricaris, Emerald Toucanets, etc were seen within 100 m of the rig. This was a small RV park called Laguna Azul and is the most delightful spot we have ever visited andplan to return.

You just have to check out your site for possible solar.

Reed and Elaine

Reed and Elaine

[pianotuna]

Hi jrn,

Make that a steam turbine.

jrnymn7 wrote:
Yeah, a wood burning stove to melt the snow... to supply the water to turn the turbine... lol!

[jrnymn7]

Yeah, a wood burning stove to melt the snow... to supply the water to turn the turbine... lol!

[Almot]

jrnymn7 wrote:
Either way, it sounds like this threads OP needs to reconsider going solar, if he plans on staying put in that nasty weather. I like the rain gutter and water turbine idea better. 🙂

Yeah. Rain is definitely an abundant "resource" here. With what OP said about camping in 40F and rain, it sounded like they were planning to go out often, not just when it's sunny in forecast. A water turbine, and maybe a wood burning stove too.

[Almot]

reed cundiff wrote:
We have six x 235 W panels (1.4 kW)

Ah, so this is 1400W total you have.

Looks like BFL was right when posting that scary picture a while ago, with his rig parked in a deep rainforest of Vancouver island. Trying, as usual, to justify his reasons to not install a big solar, - nothing new here :). Even with 700W that few of us have, this would be mere 20 AH a day, in summer. Not to mention more common smaller installs of 300-400W.

[jrnymn7]

Almot, like I said , "it's all in the wiring". Stock wiring is crap... but not that difficult or expensive to upgrade. I have read of guys bumping up their charging abilities from 7-10 amps to 40-50; and that's at 14.3 volts, not the 13.6v most converters put out. And like you said... "there is a benefit of charging on the road - IF - you move often". This applies to both TT's and MH's equally. It's not rig dependent, necessarily, but OP dependent.

Either way, it sounds like this threads OP needs to reconsider going solar, if he plans on staying put in that nasty weather. I like the rain gutter and water turbine idea better. 🙂

[reed_cundiff]

We have six x 235 W panels (1.4 kW) with about 9+ kW-hr of LFP. I wrote that we could conceivably emplace another 3 x 235 W panels for 2.1 kW. We have not found a reason to do this but we could run the AC on 2.1 kW of panels without utilizing the battery bank.

40 Ah is only 600 W-hr. You could conceivably get 40 amps at 12 V from a 700 W panel.

Our max power was 1.3 kW this summer. The most we get this time of year is 0.93 kW. The panels are ganged in two series of 3 x 30 V (235 W) panels. The voltage is thus 90 V to controller from the two gangs in parallel. So 1300 W was only 14 amps.

Our grandson changed out the charging pin so that we had a direct link to the backup video without hooking/unhooking another cable. 120 W at 12 V from the pickup's alternator is ts to the 500 to 1300 W from the solar.

Reed and Elaine

[Almot]

reed cundiff wrote:
We are currently in southern New Mexico and can obtain about 5500 W-hours a day (on sunny days) this week

5500/12.7= 433 AH.
With 700W flat panel at the end of November?

reed cundiff wrote:

We were on Olympic Peninsula for three wees this summer ... and were getting about 500 W-hrs each day in 150' trees. So, we were going down 750 or so W-hr a day. We had a 5 kW-hour deficit in the battery bank by the time we left.

40 AH a day with 700W in summer, why not. When it's clear sky over those trees, the shade isn't too dark.

On a day when my solar harvest is mere 40 AH, my batteries are floating at 100%, no deficit. But this is me. Some people need at least 3 times as much, to live comfortably. As Steve previously noted, controlling your consumption is a big deal.

[Almot]

jrnymn7 wrote:
Almot, unless I misunderstood you, TT's can have their batteries charged while traveling, as well. It's all in the wiring.

The problem with TT is that 7-pin connector from pickup allows max 10A. So, while technically you "can" charge your batteries while traveling, in reality this is peanuts. Besides, TTs tend to stay on the camp for days in row, while small motorhomes like class C tend to be on the move more.

[reed_cundiff]

We are currently in southern New Mexico and can obtain about 5500 W-hours a day (on sunny days) this week and run the Dometic fridge from inverter/solar/battery bank during daylight hours and 24 hours a day if we know it will be sunny the next day as well. The primary problem with flat panels is that you get nothing until about 9:30 am, and similarly nothing much past 3:30 pm.

We could utilize another 700 W of solar. Just went on the roof with a piece of cardboard the same size (more or less) as one of our 235 W x 30 V panels and found that three more could be emplaced.

We were on Olympic Peninsula for three wees this summer and I called the Mora CG in Olympia National Park and inquired about a solar suitable spot. I was chided gently "Sir, this is a rain forest, your solar panels will not be of much use!" We spent a week at a National Forest CG near Beaver and were getting about 500 W-hrs each day in 150' trees. So, we were going down 750 or so W-hr a day. We had a 5 kW-hour deficit in the battery bank by the time we left. We had plenty of solar at a couple of Forest Service CGs on the Oregon Coast.
Reed and Elaine
Reed and Elaine

[jrnymn7]

Almot, unless I misunderstood you, TT's can have their batteries charged while traveling, as well. It's all in the wiring.

[BFL13]

The gloomy averages should not be confused with conditions while camping though. You can pick when to go camping by the forecast.

Every so often you get a few days in a row it is fairly nice out. Your solar could do you some good while camping then--but only if your panels are out in the open.

[Almot]

pianotuna wrote:
Hi Almot,

Wow, only 28 amp-hours from 1000 watts of panels? I'm floored. On Dec 21 I get about 17 amp-hours from 256 watts of panels.

Yes. You know about PVwatts calculator. This is what it shows for Seattle in December. Enter DC Rating KW=1, Panel Tilt=0, and the result is 11 KWH a month. Divide into 31 days and 12.7V, and you will get 28 AH a day.

28 AH is average daily. With 1 good day per 3 or 5 bad days you will indeed get 70 AH or more, on a good day, from 1000W panel. And almost nothing on bad days. The thing is, the area is really rainy and cloudy in winter, not too many good days, so the average comes out very low. They could try and ride out the dark spell on batteries, but with a battery bank of usual RV size this won't be easy - and then they might not have enough time to re-charge on a bright day before it starts raining again.

I am looking at this all from TT point of view, and you are right, with Class C there is a benefit of charging on the road if you move often. So in the end this might be possible, but still difficult. It depends on how much the OP move around and how good they are at energy conservation.

Edit - PS:
As BFL have established empirically, solar harvest depends on the area, and the calculator apparently agrees with BFL 😉 . For example, same 1000W panel, according to calculator, will harvest on the average 70 KWH a month or 178 AH a day in December in Tucson AZ. Which agrees with my observations of 80-90 AH on 490W panel in North Baja in December. This is 6 times more than in Seattle. Weather pattern, i.e. number of sunny days (or sunny hours per day), does matter.

How those snowbirds in AZ with 70-80 AH a day - this is on the darkest month of season - still have to run a generator on most days, is beyond my understanding. The wives are probably to blame again, no other natural or unnatural causes come to mind 🙂