How much solar to stick on a 22-24 foot "C"?

pianotuna wrote:
For 7 grand I could have had a solar system with inverter/charger and battery bank that would eliminate generator use 100% of the time including air conditioner use.

But Don ... wouldn't it take this kind of solar to run air conditioning 10 hours a day for several days in a row genny-less while drycamping in Arizona in May ... like some of us can easily do with a $3000 genny? (just tweaking ya for fun :) ):

pnichols wrote:
Don ... comparing an RV with only generator power to an RV with only solar power is not an Apples-to-Apples comparison. A generator can supply high or low power anytime, while solar can only supply low power sometimes.

Since Don didn't cover this, I think it won't be impolite to chime in. There is not much need in high power other than when you need A/C.

And, the period defined by "sometimes" in certain states would cover about 90% of daytime hours. In fact, 100%, but 0.5A current generated by 500-600W system under heavy rain can be ignored. Don (I think) is in prairies. When snowbirds in Az are running generators - in winter! - I only shake my head :)

BFL13 wrote:
It is amusing to read PT and Almot pontificating on how the way many of us do our solar is wrong, ...

...my idea of an energy audit it to actually go camping and see how that works for you and DW. Then adjust as required.

To do something right or wrong, one has to actually do it. Running one panel from time to time when sun shines, not counting on it, not expecting much and being unable to (due to factors beyond user's control, climate among other things) doesn't represent much of a conscious doing, IMO. Referring to this as "wrong" or "right" would be meaningless.

The factor of DW or children is a variable that can not be measured, predicted or estimated and can indeed render any logic and science fruitless, agreed :). Doesn't mean that these methods don't exist or can not be used.

Nobody suggested to "forget" about portable. But portable is an added pain, especially in motorhome where you don't have a pick up truck, and if having more roof solar allows not to have a portable, then this is preferred way.

Hi BFL13,

I have a modest 256 watts of solar which I used to keep up an 875 amp-hours of battery bank. I separated the bank and was able to equalize, when the RV was in storage. Cost $1700.00.

Solar output, in leafy shade, is 7 amps from 90 minutes before solar noon to 90 minutes after solar noon. I don't have figures for when charging starts or when it ends in leafy shade--but if I stay off the inverter I don't run out of power (with the current house bank of 566 amp-hours).

Before that I had 30 watts of solar which serviced 250 amp-hours of battery bank. Cost $1700.00

I agree it is situational. But with the advent of the Grape solar controller (with temperature compensation) it truly is not needful for small to medium systems to have more than one controller. A second controller for portable panels is not necessary. Just a couple of switches that allow roof on / off and portable on /off and a connector for the portable panels.

An energy audit allows a better estimate of battery bank sizing. If one wishes to consume the batteries--then solar is 100% optional and probably not needed. If long life is wanted--then solar can really shine.

Now that I'm full time, I could put a 2000 watt system to good use. Before that, the 256 watts with the large battery bank meant I ran out of fresh water before I ran out of power.

For me, shore power has to be paid for as I am full time. I do agree that equalization can be done.

BFL13 wrote:


On equalizing as a measure of solar required, most folks would never have to do that on solar. They can equalize other ways--such as when on shore power from time to time.

Why tell somebody they need so much solar to just go camping? All they need is a way to stretch out the time before their batteries get down too far before going home and plugging in.

There is no sense in advising people to put more solar on the roof and forget the portable solar, when their scenario is that the roof is under trees and the portable is set out where it can catch some rays.

If somebody is adding solar and wants to use a second controller with the added solar, instead of tossing his existing set-up, why not? It works.

It is all situational for what is the best advice.

Hi Phil,

For 7 grand today, I could have a solar system with inverter/charger and battery bank that would eliminate generator use 100% of the time, including air conditioner use.

pianotuna wrote:
Then folks complain about the one time cost of solar? It makes no sense to me. Even if I go with the 2005 price of $5 per watt for 7 grand I could have had 1400 watts of solar.

Don ... comparing an RV with only generator power to an RV with only solar power is not an Apples-to-Apples comparison. A generator can supply high or low power anytime, while solar can only supply low power sometimes.

Sorry that you've had such bad genny luck. We've had the same stick house backup power contractor style generator for >15 years, the same camping portable Honda generator for >25 years, and the same built-in Onan RV generator for >11 years.

Of course, the (almost) ultimate camping power setup is to have both generator power and solar power.

PT, sorry for your bad luck with generators (and inverters).

On equalizing as a measure of solar required, most folks would never have to do that on solar. They can equalize other ways--such as when on shore power from time to time.

Why tell somebody they need so much solar to just go camping? All they need is a way to stretch out the time before their batteries get down too far before going home and plugging in.

There is no sense in advising people to put more solar on the roof and forget the portable solar, when their scenario is that the roof is under trees and the portable is set out where it can catch some rays.

If somebody is adding solar and wants to use a second controller with the added solar, instead of tossing his existing set-up, why not? It works.

It is all situational for what is the best advice.

Hi BFL13,

Just a range of opinions. I'm on the low side at 60 watts per 100 amp-hours of storage as a minimum to equalize. Then Mex came into our RV lives and confirmed that number.

For maintenance between trips 15 watts per 100 work, and may even slowly recharge the battery bank.

Your own back yard experiments on charging prove out the upper limit of 150 watts of solar per 100 amp-hours of storage--for tapering at 85% state of charge is pretty much dead on 150 watts (~12 amps).

The above suggestions may not work in "the land of trees".

I'd never have the patience to do a "tilt-a-whirl" as you have in the past done--but you do get more watts to harvest that way.

I've spent more than quadruple the cost of my solar system on generators. My Kipor was good for 8 years @ $1250 Cdn, its replacement (Boily) never worked properly from get go @900. Then I joined the big time and got the Yamaha sIEB for $2200 Cdn plus 500 US for a Pinella's remote plus $100 for installation of the remote. In the fall of 2016, someone "helped themselves" to the Yamaha. Cost to replace it was $2700.00 Cdn. The insurance covered just $1250. I have not submitted the bill yet for the remote, but I imagine the same level of support will happen.

So

1250 Kipor
900 Boily
2200 Yamaha
700 Pinella remote
1450 (out of pocket for replacement Yamaha)
500 remote replacement (this is a guess)

$7000.00 for the "parts" for generation since 2000. vs $1700 for 256 watts of solar that has not cost me a dime to keep running.

I filled the generator only 5 times in 2016.

Then folks complain about the one time cost of solar? It makes no sense to me. Even if I go with the 2005 price of $5 per watt for 7 grand I could have had 1400 watts of solar.

I've spent less than $100 per year on my house and starter batteries, from having a solar system.

BFL13 wrote:
It is amusing to read PT and Almot pontificating on how the way many of us do our solar is wrong, silly, or just awful. Newsflash! Other ways do work just fine thank you very much. :)

BTW, my idea of an energy audit it to actually go camping and see how that works for you and DW. Then adjust as required.

My energy audit consisted of reviewing how much of the sun's energy hitting the roof could be harvested in a practical matter.

It is amusing to read PT and Almot pontificating on how the way many of us do our solar is wrong, silly, or just awful. Newsflash! Other ways do work just fine thank you very much. :)

BTW, my idea of an energy audit it to actually go camping and see how that works for you and DW. Then adjust as required.