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

[Almot]

Snowman9000 wrote:

Maybe their controller was a long way from the batteries, with thin wire from there.

Probably. And/or wrong controller, wrong setpoints, no temperature compensation. And the loads with current and wattage that they don't know. Exactly what Handy Bob observed in snowbirds camps - solar systems installed by somebody who didn't know what he was doing, and the owner doesn't know and doesn't really care what he is doing either.

[jrnymn7]

Are the smaller Honda gennies capable of a remote start set-up?

edit, never mind, I found only the pinellas one.

[jrnymn7]

x2 on a honda eu...i gennie (2000 or 3000)

snowman, I look forward to seeing your data, as I'm very curious how much a flat install loses, late fall to early spring. Let's face it, no one wants to have to lug panels around, but it seems the increase in Ah's makes it well worth it, especially in the darker months.

Personally, I need to come up with several mounting strategies, to suit my various parking situations, and to keep my panels off the ground as much as possible. And rv manufacturers need to get their sh*t together, and start roughing in the wiring for solar installs. No one should have to run wires thru their fridge vent, for example.

[pianotuna]

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.

I agree that the first order of the day is to conserve. LED lighting at the prices we can get from Ebay is a no brainer.

Next on the list is stopping both heat build up in summer and heat loss in the winter. I use vent and skyline "cushions" and have insulbright covers for the windows, door, and a way to block off the cab area. Doing so means I can heat 100% electrically in winter using about 19000 btu's (~6000 watts), while keeping the propane furnace as a "back up".

Next stop is upgrading charging paths from the alternator. I added a second charging circuit, so I have twin #8 wire. This allows me to do 70 amps when needed. Even at highway speeds my system can not sustain 70 amps for long, so I've been known to limit the charging by turning off one wire, and also to shut down some of the loads.

What I can run is the fridge and the fan for the roof air. Running the fan allows me to cool down the RV using the dash air.

The Magnum inverter allows me to run what ever I wish from the batteries, but that energy has to be replaced. I have done experiments where I use 1300 watts to run the water heater. I watch the voltage on the chassis and use a duty cycle of five minutes on and ten minutes off. My "cut off" is 13 volts. If I see that I shut down some of the loads.

There would be room for improvement on the alternator by adding a remote regulator to take the load off the internal diodes. Another more expensive route would be adding a second alternator, dedicated to the house batteries.

One of the summer problems I still have is heat build up in the drive train. After I've driven for several hours it takes a heck of a long time to cool off--and of course that heat does rise and warms the RV considerably in the summer time. I've toyed with the idea of using a box fan under the rv to blow away the heat, but have not actually tried it.

I'm still "on the fence" about upgrading the solar. What I have works well, more by luck than good planning. Upgrading to more wattage might not make the difference I hope for. Living off the grid entirely with solar for electrical power is the goal. I would snow bird from November until March each year.

When I went to full time, I did purchase a Yamaha Sieb 3000 VA generator. I've since added remote start for that and combined with the hybrid inverter I can run everything I want to without fearing running down the battery bank.

The combination of the hybrid inverter and battery bank allow me to use just 15 amp shore power while retaining the ability to run every item I wish to at the same time. Of course, I can't exceed the 3000 watt rating on the inverter, but it is miles better than having to load balance and agonize about tripping a shore power breaker that I don't necessarily have access to.

If someone would make a truly flexible panel, I'd consider replacing the awning. That would be a wonderful way to have the best of both worlds. I.E. keeping the existing solar while adding a lot of capacity.

[Snowman9000]

Almot wrote:


Same as Steve, I don't feel like I need more solar (with my 490W). But I constantly see people with same size solar running generators 6-7 hours a day, on the same camp in the same weather. First I asked, for curiosity, then stopped. They either can't provide any explanations, or mumble something about the wife that "wants to do many things at the same time" - have no idea what this could mean. None of them bothered converting lights to LED, none have proper 12V fans for hot weathe, and most of them spend many-many hours in front of their TV sets (which are usually also not the most modern and efficient).

You sound like Handy Bob. 🙂

Maybe their controller was a long way from the batteries, with thin wire from there.

I'm finishing up my roof install now. The process has showed me that there are so many ways a solar package could be screwed up, it's not funny. It's one thing to read about solar here. It's another to figure out exactly what to buy and where to put it in the tight confines of a small Class C with batteries in the step well. Despite how mature the solar industry is becoming, there is still a lot of adaptation, trips to the hardware store, and problem-solving needed for RV installs.

Mostly I'm talking about specifying/purchase decisions. Plus poor installation. Panels too close to objects on the roof. Wire size & length. Lossy circuit breakers. Poor connections. Poor controller or settings on same.

[Snowman9000]

Starting sometime in January in AZ, I'll be collecting off-grid data on 300W flat on the roof versus 100W portable on the ground. Also trying at least two different PWM controllers. One is single stage, it will stay at 14.x, temp compensated. The other is a newer version of the same model, temp-compensated 3 stage with bulk, then 3 hour absorption, then float. Will be interesting. I will be using a meter that tracks AH in and out. I hope to post a daily log like Mr. Wizard did for a while.

If anyone wants to send me any other controllers to test, let me know. I'll mail them back no later than mid-March. I'm not expecting anyone to send me their controller, but if you want to, I'm game. There are "tests" on youtube that are not worth the time it takes to view them. Even here, there is a real lack of comparative data, I think.

[Almot]

NinerBikes wrote:

With what you tell me, and not sacrificing, and where you camp, and how much roof you have on a C class...I'd sell your 1990's generator, and get a new Honda Eu2000i Generator online from Wise Sales. Maybe a good 14.8V charge controller too.

Somehow I missed that it was class C.

With class C - Pianotuna could tell something more, though in his inland area, even though darn cold, he is getting more sun in winter than in coastal WA.

I would say - forget about solar in winter in WA with class C. Wrong location, wrong season, and wrong RV, too small roof.

Maybe get some portable 100-200W, no need to install anything. Inevitably being tilted and TAD tracking, 200W portable will work like ~300W flat, in this area. It will let you live without generator on some days in summer, when it doesn't rain.

Path1: what Steve in Oregon wrote about 300W solar - not that I disagree. Technically, possible. Though OR is a little better in winter than WA, and as noted, you have to be very good at energy conservation. If the approach is "why bother going RV if we can't use everything that is in there" (i.e. all 110V devices and more) - it's not going to work for you.

Same as Steve, I don't feel like I need more solar (with my 490W). But I constantly see people with same size solar running generators 6-7 hours a day, on the same camp in the same weather. First I asked, for curiosity, then stopped. They either can't provide any explanations, or mumble something about the wife that "wants to do many things at the same time" - have no idea what this could mean. None of them bothered converting lights to LED, none have proper 12V fans for hot weathe, and most of them spend many-many hours in front of their TV sets (which are usually also not the most modern and efficient).

[Almot]

BFL13 wrote:

To live the same way for microwave etc, exact same standard of living, with our rig (a barn to heat) it takes 200AH/day at 35F in February. But it takes maybe 70AH day to do the same in summer at 80F out in the open (long warm days means few lights and little furnace)

Heating in your RV, same as 99% of them, is not optimized for offgrid on solar.

But, with estimated average daily harvest 28 AH from 1000W flat panel in this area in December, I can hardly see myself doing it even if heating would come from some magical source. Especially if the week when I camp would get less than average sun (read - 20 hours of rain every day for a week). Winter here sucks, big time.

[NinerBikes]

path1 wrote:

NinerBikes wrote:

OP needs to tell us more about the rig he is in, what they use that sucks power, and wifey habits. Obviously, hair dryers, and A/C's and microwaves may be out of the picture, without a generator if in a smaller rig.

OP here....More info if it will help.

We just brought wives TT home last month. We have RV'd for many years and have had several RV's (actually too many). The latest is a 2013 Arctic Fox that and it is the wives. We love to travel in our X-rental Majestic that replaced our 37ft 5th wheel six years ago and will keep it. The places a small class C can get into are great. But as about everything else in RVing there are compromises. One of the compromises is the size of RV. Small class C is great for shorter amount of time, but when its raining or staying put for longer time, they are not so good for us!.

We wanted something that we would be more comfortable for staying put for longer time and more room especially in the kitchen area. Overall be more comfortable.

Talking with people that do have solar we've noticed that some people want to power a small city and others say they should of put up more.

Being we seem to blast thru batteries, we thought why not get some solar? Most of our camping trips are in the winter time the temps are in the 30-40's and raining. But our lack of sun in the pacific NW we'll probably need more than the usual. We are going to start our "going south" again to warmer climate as soon as wife gets OK from her Dr.

So knowing nothing about solar, I thought others might chime in and atleast get us going in right direction. Our elec usage IMO is "normal" we like temps 70-72 degrees and wife will read 1/2 the night with some lights on. IMO wife is not as conservative as she should be, but that's OK, she thinks we'd get better MPG if I didn't bring so many tools and spare parts along. But she doesn't complain about my shop labor rate when something needs fixing and I don't complain about all the gadgets or weight of them in the kitchen. So I guess we're even.:B

Our generator is an old Honda (1990's model)that is not so quiet compared to newer light weight ones, so we don't use it if we think it will disturb others. And I thought we might be able to leave generator at home with enough solar being tow rig is an older diesel. That would be no gas and gas cans.

I'm starting to read some of the links people have posted and starting to believe solar is like tire posts. What works for some doesn't mean it will work for you.

Maybe my question should of been, how much solar do you have and do you like it?

Thanks

With what you tell me, and not sacrificing, and where you camp, and how much roof you have on a C class...I'd sell your 1990's generator, and get a new Honda Eu2000i Generator online from Wise Sales. Maybe a good 14.8V charge controller too.

[MrWizard]

JiminDenver wrote:
I don't use the panels to charge a big bank that I drain over night. I use it to power the things we do during the day. Coffee, cooking, heating water, TV/Sat, cooling the trailer, even some heating on those cold clear mornings. In the two weeks we used the two 245w systems, the controllers recorded a little over 16000 Wh.

that avg 1142 watt hrs about 83 amp hrs per day

very doable.. works very well

a longs ways from RJ's comment that i originally refered too

enjoy it..

[SteveAE]

Path,

You asked how much solar we have and if we like it.

We have 300 watts of solar and love it. Never have felt the need for more. We mainly boondock in Oregon, in the winter (just returned from the Steens and Alvord Desert....yes, during the recent cold snap....and the lowest the batteries dropped was to 83% .... before compensating for the 5 degree temps). We don't have a TV, but run everything except the AC (including the microwave when charging conditions allow). And I have yet to even start my generator on a camping trip (should just get rid of it, but it is nice to have at home.....).
When we go to the Oregon coast (in the winter) and stay in the State parks, sometimes I don't even bother to plug into their power....I forget. No big deal, the solar almost always provides a little (even in the rain) and we have enough batteries to carry us though for about a week in that easy climate.

As you can see, I differ in opinion from some others on this, but hey, it works for us. I suspect the main difference for us is that we usually only stay in one spot for two or three nights before moving on (usually plenty of solar charging going on when on the road). Perhaps not having a TV helps some too. During the day, we are usually out hiking or skiing/snowshoeing so power consumption then is very minimal. And of course it helps that my wife is very good at checking the Trimetric before turning on the inverter to run the microwave.

Solar is only part of the equation. IMO power consumption and storage capacity need to be addressed equally.

You will love solar. Just do it.

Steve

[JiminDenver]

I don't use the panels to charge a big bank that I drain over night. I use it to power the things we do during the day. Coffee, cooking, heating water, TV/Sat, cooling the trailer, even some heating on those cold clear mornings. In the two weeks we used the two 245w systems, the controllers recorded a little over 16000 Wh.

[MrWizard]

JiminDenver wrote:

MrWizard wrote:

Never have I read about an RV`r saying they got 600 amp hrs in a day
I think you have a typo confusing watt hrs and amp hrs
600 amp Hrs would be way over 7000 watt Hrs...approx 8000 watt Hrs

I looked, a amp hour is the same now as it was 35 years ago. use one ampere for one hour and it is one amp hour. 50a for one hour is 50 Ah. 50a for 12 hours is 600 Ah.

I designed our system to be able to run a small air conditioner without draining the battery. I'm looking into options for the power that isn't being used.

Your math is correct..But amp hrs and watt hrs are different...remember Watt Hrs is Amps * voltage... 50a*13.8v = 690 watts * 12 hrs = 8280 watt Hrs

600 watt Hrs is fairly easy to achieve...today my system produced 63.07 amp hrs. Aka 883.9 watt hrs

But I said I never "READ" any RV owner user saying their system produced that (600 amp hrs) per day

We had one member off grid in Texas with his TT roof completely covered...a/C moved too basement
And he had diesel genset on auto start..when his a/C kicked on

And to make use of 600 ahr daily charge you need a very large battery bank
You will not get 50ahr for 12hrs
To avg that with flat panels you will need about 2000 watts of solar panels

[jrnymn7]

Thanks, BFL,

Yes, having considered all that, I was thinking in terms of time and place being the PNW in late fall, early winter... i.e; the OP's situation. Assuming solar would even work there at that time (I'm not familiar with the weather there), what would it take for the flat to reproduce the power acquired by the tracked solar? I have to imagine the spread between the numbers you provide would only increase.

[BFL13]

Almot wrote:

Canadian Rainbirds wrote:
My solar, 420 Watts, and 484 AH of battery is almost enough for the winter in Mexico (without AC) and the same up here in the summer if we're not under the trees.

Yep. Minimum 500W for winter in Mexico or summer in BC-WA. Make it 700-1000W to be able to camp in partial shade too.

Winter in WA, on solar, jeez... I can survive on zero watts when it's warm and dry in daytime. When it's 40F in the night AND in the day and rains non-stop for a week - I wouldn't even try living without 110V grid, or a wood burning stove, or a generator.

To live the same way for microwave etc, exact same standard of living, with our rig (a barn to heat) it takes 200AH/day at 35F in February. But it takes maybe 70AH day to do the same in summer at 80F out in the open (long warm days means few lights and little furnace)

We have 230W of solar in a tracking contraption and get by with very few generator runs (only due to poor weather at times) from May to September. 230w tracking there, then, would be like 370w flat.