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Old 07-03-2020, 09:16 PM   #1
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2020 20' Bambi
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Solar and Relevance to Long Off-Grid Trips

Folks, I am reading as much as possible but I have some logic issues. On the Zamp website related to portable units they tend to imply the bigger units are better for longer off-grid trips. I sent this email to them but would like to hear anyone else’s thoughts on my logic.

Zamp: On your website, in the product promo for the 230 Watt portable you state “ Our biggest, most powerful portable solar kit generates 230 watts at 12.6 amps—enough for large RVs and long off-grid trips.”

What does the size have to do with length of trip in relation to your reference to “long off-grid trips”? If the solar panel is only generating energy when the sun is out, which occurs on a partial daily cycle, and it only charges the battery to top it off daily, depending sun exposure and your usage, it has to repeat the process daily, regardless your trip is 2 days or 20 days. So in fact it is only enough for charging daily regardless the length of your trip and the length of your off-grid trip is irrelevant with respect to the size of the unit since the limiting factor is your battery bank size, useage and the fact the charge controller cuts off to prevent overcharging. Am I not correct? If incorrect, please explain if you don’t mind so I am clear about the panels.

ASForum folks, am I missing something here?
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Old 07-03-2020, 10:04 PM   #2
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You aren't missing anything except perhaps a realistic expectation that they would not use cute marketing language in advertising . I've had these same thoughts as a solar fan, but it's not false advertising.

The main reference too big RVs is that it's over 200 watts.

What scares me more is when people think they will get the advertised max every time they point it at the sky.

Edit:
Unless you know how much power you use daily, it's effectively impossible to guess how big you want to go with the solar.
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Old 07-04-2020, 05:39 AM   #3
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Quote:
Originally Posted by CampingDavid View Post
You aren't missing anything except perhaps a realistic expectation that they would not use cute marketing language in advertising . I've had these same thoughts as a solar fan, but it's not false advertising.

The main reference too big RVs is that it's over 200 watts.

What scares me more is when people think they will get the advertised max every time they point it at the sky.

Edit:
Unless you know how much power you use daily, it's effectively impossible to guess how big you want to go with the solar.
Camping David, Thanks for your thoughts. I can agree related to the part of the quote referencing bigger RVs. But the part that suggesting having a larger watt panel allows for longer off-grid trips is coming fairly close to false advertising. At least it is very misleading. Given two RVs with same power consumption needs sitting at same boondock location, with two AGM 24T batteries and same daily sun if a 180 watt solar panel keeps the batteries fully charged each day until sundown then having a 230 watt solar panel does the same but produces excess power that can never be used by the batteries and that additional 50 watts does not allow you to take longer off-grid trips. Being honest with myself, I was not smart enough to think this through prior to buying the 230 watt portable when there is very high probability a much smaller unit would suffice. The “longer off-grid trips” reference was a driving force in my hasty purchase.
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Old 07-04-2020, 06:05 AM   #4
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Quote:
Originally Posted by smsasf View Post
Folks, I am reading as much as possible but I have some logic issues. On the Zamp website related to portable units they tend to imply the bigger units are better for longer off-grid trips. I sent this email to them but would like to hear anyone else’s thoughts on my logic.

Zamp: On your website, in the product promo for the 230 Watt portable you state “ Our biggest, most powerful portable solar kit generates 230 watts at 12.6 amps—enough for large RVs and long off-grid trips.”

What does the size have to do with length of trip in relation to your reference to “long off-grid trips”? If the solar panel is only generating energy when the sun is out, which occurs on a partial daily cycle, and it only charges the battery to top it off daily, depending sun exposure and your usage, it has to repeat the process daily, regardless your trip is 2 days or 20 days. So in fact it is only enough for charging daily regardless the length of your trip and the length of your off-grid trip is irrelevant with respect to the size of the unit since the limiting factor is your battery bank size, useage and the fact the charge controller cuts off to prevent overcharging. Am I not correct? If incorrect, please explain if you don’t mind so I am clear about the panels.

ASForum folks, am I missing something here?

Last Season we did a 7k Cross Country without deploying our 360w of Zamp Suitcase.🤔

It really depends how long you are not moving. Four days our longest without shore power.
The rest of the stationary time we did have SP.

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Old 07-04-2020, 06:30 AM   #5
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Anyone who has 'solar' on the roof knows that panel production is heavily dependent of sky conditions. The used AS I purchased in 2016 came with ~ 160 Watts of panels that are managed through a Zamp 5 stage controller.

During the day the controller tallies the amp hours delivered by the system. The day to day variations in output are significant. Large solar farms utilize advanced camera systems to track clouds in order to predict output variations.

On an RV scale how long you can boondock on a set of panels is heavily dependent on weather, sky conditions, and probably time of year. I suspect many people walk into this process without understanding the variablities in play.

Best of luck in developing your solar solution. There is lots of expert comments on these boards about solar systems. Lots of great lessons to be learned.
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Old 07-04-2020, 09:36 AM   #6
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It is clearly a marketing department issue. They needed to differentiate the larger product from the smaller one and it flows well to say that the larger product is for larger/longer applications.

You need to evaluate your needs. What you need and what the solar system generates are wildy variable depending on season, lifestyle and weather. In my opinion, solar can provide what you need some of the time. You will still need a generator every so often. The bigger the solar the less often you will need to run the generator.
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Old 07-04-2020, 09:36 AM   #7
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Hi

Bigger is always better

If you are out for a weekend, you start with fully charged batteries. The *assumption* is that your batteries are "ok" for at least two days. In this case, the solar only has to "make up" for about half a day (or less). It's more a "just in case" than a "gotta have".

If you are out for weeks at a time, the math is a bit different. The same batteries are not enough to run for a significant fraction of this time. You *must* get enough out of the solar every two days to keep things going.

If you are in the shade and it's cloudy / raining solar isn't going to do much for you. It's very easy to "loose" a day this way. Now your setup has to produce two days of power in one day.

If the shade in your campsite is pretty deep, you may only get half what you expect ( I've seen a *lot* less than that ...). Double the panel size again.

If it's late (or early ) in the year, the sun isn't up as long. It's angle is not at all ideal for roof mounted panels. Double (or triple) the panel size vs high summer out in the desert.

The more you travel, the more you will run into all this stuff.

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Old 07-04-2020, 10:06 AM   #8
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Excellent answer Uncle_Bob. I will add that my goal with solar is to produce enough AH each day to fully charge the batteries and live continuously without the need of shore power or generator charging. I use the energy that my panels produce.

When I'm camped under a fairly thick canopy of shade trees, my usage may be as little as 25AH per day. Keep the lights off, use fantastic fans sparingly. Don't camp there if you want to watch the NASCAR races on TV over the weekend. Better not use the furnace.

When I'm camped where I get six hours, or more, of good sunshine. Turn on the fans to stay cool. Turn on the inverter and watch TV. Use the vacuum cleaner. Charge up all the battery powered appliances. Use all those cool indirect lights on the Globetrotter. Heck, turn the refrigerator to DC during sunlight hours to save some propane. 150AH of use in a day, no problem, the batteries will still be fully charged by evening. Then run the furnace all night long and repeat the process the next day.

Then like Uncle_Bob said, all of this depends on the month of the year. Summer months are sunnier, with longer days, and better sun angles. I could get by on half the panels in the summer than in the winter.

Bottom line for me is to buy as many solar panels as will fit on the roof, can be stored if portable, or you can afford. Then live on the power that is produced.
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Old 07-04-2020, 11:30 AM   #9
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Bottom line is larger watt panels provide a larger margin to obtain enough power to get you through more days. I have the 230 Watt zamp portables with lithium batteries and have gone 10 day in the west running the furnace and cpap machine each night. Temps at night were in the low 30 degrees. The lithium’s accept charge more easily than Lead Acid batteries and I believe that it the reason we did well on the trip. We did have sunny days and was able to move the panels to the sun. Don’t know if this helps but are my thoughts.
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Old 07-04-2020, 12:09 PM   #10
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I RV off the grid more than not in my Flying Cloud 20 - and at least once a year for a full month without moving.

You need DIRECT SUNLIGHT for a few hours to recharge half-depleted batteries. Adding panels will not help much if you don’t get direct sunlight. Extra panels will reduce the charging time which is very long if not in the sun. I use two Zamp 160w panels, mostly so I don’t have to be around to continually move a single one into direct sunlight. 160w kept in the sun for a few hours will do the trick. Its more critical to get that direct sunlight than buying a bunch of extra panels. Again, DIRECT SUNLIGHT!

While in direct sunlight, you can run the fans on high, use the inverter, and take a luxurious shower. When not, I suggest running one fan on low, inverter off, and water pump sparingly to assure you can run the furnace to keep you from freezing at night.

For example, I spent a month in Yellowstone in a mostly shaded spot. With two panels and planned noontime returns to the campsite to avoid crowds and get the maximum positions for the panels on sunny days, I used less than 2 gallons of gas to run the generator after cloudy days for the entire month.

If you are moving every day or two, your tow vehicle will provide somewhere in the order of 1200w for charging. So, a couple hours on the move will charge them right back up.
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Old 07-04-2020, 02:08 PM   #11
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In advertising "puffing" is legal, but I'm not sure about politics.
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Old 07-05-2020, 09:59 PM   #12
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I am sympathetic to your complaints about advertising. It's bad advertising, but not technically "false" advertising as defined to a point where you could force a change.

I always take my generator and hope I don't have to run it. I would love to be fully energy independent, but I can't control the sun and sometimes can't set-up with clear sky access (nor do I want too.)
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