Efficiency of flat fixed solar vs adjustable portable?

[JaSAn]

. . . When my camper target weight is 650 pounds adding a second solar panel, 25 pounds, and a second battery, 55 pounds or 80 pounds is huge! So can I make what I have more efficient? . . .

IMO if you are trying to minimize weight the lightest you can go is fixed flexible panels on the roof and LIFePO4 batteries. You are trading weight for $$$.

One thing I haven't seen discussed is with flex panels used as portables: one must provide structure to hold them rigid as they are aimed at the sun. The structure can equal or exceed the weight of a second flex panel.

As to batteries I don't understand your issue. The battery weight will be the same for fixed or portable panels. Your batteries are sized to run your loads and your charging system is sized to refill the batteries every day.

jim

 

[Vic Harder]

Wow, great thread. Best thought so far is that "a 100w portable/suitcase is able to recharge batteries equally as well as a 160w flat fixed panel...if you're moving the portable to track the sun all day".

I have yet to try out my solar setup.... real soon though! On a "rest day" in the forest I will likely be using my portables. Most often not, as the truck/camper will be parked at a trail head. Too tempting for folks if the portables are out and deployed, so the roof mount will have to do the trick.

BUT, given Boonie's weight goals, I think maybe making the roof mounts easily dis-mountable for portable deployment might be worth looking at. And I would look at 2 100W flex panels. My reading of the info out there is we need 2x the AH of the batteries to ensure good recharge levels.

 

[Bill D]

My reading of the info out there is we need 2x the AH of the batteries to ensure good recharge levels.

That's a good rule of thumb that I never heard of. Thanks for sharing that tidbit.

 

[Squatch]

In my limited testing under bad cloudy conditions, mid winter. My 100w poly portable will "roughly" double the amperage going into the battery through my Trimetric. My roof panel is a 160w mono.

I can't wait for a day with some real sun to get a better handle on how much the portable adds.

One thing no one has brought up. WIND! My roof panel is solid as a rock as is the camper in a bad storm on the beach in NC.

It doesn't take much of a gust to put the portable as risk of falling "glass panels". I haven't fullly worked out my leg system yet. but to prevent being blown around in modest winds it would have to be staked or weighted.

 

[ntsqd]

Based on that RoT I'm going to need to quadruple+ our 100W solar wattage. Which is going to mean roof lifter thingies.....

Saw a simple trick at a flea market in Bullhead City, AZ couple months ago. One of the vendors used 4 of those collapsing 5 gal. water jugs as anchors for the E-Z-Up in their parking lot stall. Filled with water during the day, poured back into their RV's water tank when done. I'd guess one of these tied to the apex of the portable's 3 legs would do the trick.

 

[JaSAn]

My reading of the info out there is we need 2x the AH of the batteries to ensure good recharge levels.

That rule of thumb was developed for fixed locations that have neither real estate nor weight issues. If you can fit it, it won't hurt (one can never have too much solar). I used HandyBob's minimum rule of 1X battery AH. I am seldom below 100% in the evening.

Your requirements are specific to the latitude you camp at, what time of year, the amount of cloud cover, and how many watts you use per day. There are many calculators out there, although most are geared to tilted panels it will give a general idea of how much sun to expect. I use this chart:

http://www.solardirect.com/pv/systems/gts/gts-sizing-sun-hours.html

jim

 

[Happyjax]

In my limited testing under bad cloudy conditions, mid winter. My 100w poly portable will "roughly" double the amperage going into the battery through my Trimetric. My roof panel is a 160w mono.

I can't wait for a day with some real sun to get a better handle on how much the portable adds.

One thing no one has brought up. WIND! My roof panel is solid as a rock as is the camper in a bad storm on the beach in NC.

It doesn't take much of a gust to put the portable as risk of falling "glass panels". I haven't fullly worked out my leg system yet. but to prevent being blown around in modest winds it would have to be staked or weighted.

Squatch, when you figure out that leg system let me know. I haven't come up with one either

 

[DavidGraves]

Howdy all

We all know about the aftermarket adjustable wind deflectors commonly seen on pickups towing 5th wheel campers.

The are lightweight aluminum, easily adjusted for angle and secured by suction cups and straps.

I have one to use as a donor for the angle tilt portion to make an easily adjusted panel.....not sure yet about fixed on roof or temporary on truck hood etc.

On another consideration, my T100 windsheild lies at about 45 degrees.....suitable angle for the Northwest and BC...I might instead just bungy it there....we mostly boondock and can position truck anyway we want in most instances.

DavidGraves

 

[Vic Harder]

That rule of thumb was developed for fixed locations that have neither real estate nor weight issues. If you can fit it, it won't hurt (one can never have too much solar). I used HandyBob's minimum rule of 1X battery AH. I am seldom below 100% in the evening.

Your requirements are specific to the latitude you camp at, what time of year, the amount of cloud cover, and how many watts you use per day. There are many calculators out there, although most are geared to tilted panels it will give a general idea of how much sun to expect. I use this chart:

http://www.solardirect.com/pv/systems/gts/gts-sizing-sun-hours.html

jim

I am looking forward to seeing how well all this stuff works. soon now!

 

[DavidGraves]

Hey Vic

When does the sun come out in Alberta ? LOL

Actually we just had the first day of Spring on the north Oregon coast.....first day of Summer will be July 7th.

David Graves

 

[Cayuse]

That rule of thumb was developed for fixed locations that have neither real estate nor weight issues. If you can fit it, it won't hurt (one can never have too much solar). I used HandyBob's minimum rule of 1X battery AH. I am seldom below 100% in the evening.


jim

I'm also using approximately 1X AH (200W flat mount on the roof, 210AH) and am usually fully charged by early afternoon.

 

[Vic Harder]

Hey Vic

When does the sun come out in Alberta ? LOL

Too funny! It is out, and the portables are deployed for testing purposes. Camper isn't on the truck yet, as I am still working on my total gut and redo. Down to small details right now, including the truck wiring for the ACR remote switch and gauges in the truck.

 

[Vic Harder]

I'm also using approximately 1X AH (200W flat mount on the roof, 210AH) and am usually fully charged by early afternoon.

I have 250AH of battery, and 265W on the roof and 310W portable for my solar. MOST days I anticipate that either the roof or portables will be doing the job while the other is in the shade or in storage. So, roughly 1:1 for me too.

 

[Boonie]

Because of the inefficiency of the flat fixed panel, I will be using a 160w on the roof and 100w portable with a single 120AH battery. As Vic said using either/or panel array depending on location. Again because of my intentional low requirements, these should meet my demands (30AH/day).

 

[cwdtmmrs]

Boonie, I doubt that you will even get close to 30AH/day. Probably less than 20AH/day. With your walk through design, you could use the truck's heater as well as a auxiliary hot water heater from the engine in the camper to get the temperature comfortable and then switch to a Wave heater to maintain. I don't even think you need solar, much less 260w. Just say'n.

cwd

 

[Boonie]

CWD,
My 30AH calculation was done some time ago and included a constant .5AH draw for a solid state refrigerator. The old fashion 3-way frig I will be using will not have that draw, so your assumption of probably less that 20AH is pretty close. As stated above based on my camping location, I anticipate using either the roof or the portable, but not both at once. With a 20AH daily draw I would be down to 50% battery in 3 days, so unless I run the engine to recharge the battery, I will need the solar.

The heater in the camper is only to take the chill off a spring/fall morning, so engine heat could work if I started the engine (350 chevy, headers and 3" exhaust) every morning, but staying with a Wave or Mr. Heater makes more sense.

 

[Bosque Bill]

One thing no one has brought up. WIND! My roof panel is solid as a rock as is the camper in a bad storm on the beach in NC.

It doesn't take much of a gust to put the portable as risk of falling "glass panels". I haven't fullly worked out my leg system yet. but to prevent being blown around in modest winds it would have to be staked or weighted.

This is not a point to be ignored, as I recently learned the hard way. First night camped on the White Rim Trail earlier this month, a strong wind came up during the night. I had deployed my portable panel to catch the morning sun, instead it caught a sharp rock on its face when the wind flipped it during the night. The tempered glass was totally shattered. Interestingly enough, the panel continued to work through the trip, but only at about 1/3 of its usual output.

I'm replacing the 100w portable/deployable panel (but will be more careful and lay it flat overnight.) I am also going to add a second 100w panel to the roof. This will give me the best of both worlds: I can aim the deployable panel at the sun when I need a boost, but the roof unit will work all mid-day. There is definitely some overhead in time and effort to deploy the portable panel, so if my batteries are well charged I'll skip that step. Yet, if I set up with the camper in the shade, my cable is long enough I can set the portable out in the sun.

In fact both panels arrived today from Amazon. They have a slightly lower profile than the old one, though length and width are the same. They also weight 18# each, where competitor's panels are 20#. These are polysilicon from Windy Nation.

I found this thread while trying to figure out how much air gap to put between the solar panel frame and roof when I fabricate my custom mounts. Any suggestions? I'm thinking about half an inch to keep the overall profile low, but still allow the heat to escape.

 

[Squatch]

I had my camper in the garage painting the bottom. No sun on the roof panel for over a week and a little bit of draw. The battery was down to around 89%. I hooked up the portable 120 watt panel and instantly had 6.6 amps charging at 9am in bright sun. it had the battery back up very quickly.

 

[Rockcod]

Not sure this is the right time/place to ask, but are most running the portable panel through, the house controller or an independent controller supplied with the portable .?

Thanks

 

[Boonie]

Squatch and Bosque Bill,

An idea from the RV world many RVers use a filled 1 gal. water jug to hold down their satellite dish, so not much weight to carry, but wastes a gallon of water that for boondocking will not work. Tent stakes makes more sense but a PITA every time you move the portable.
I guess it beats shattered glass.

Rockcod,

I also use my portable in my Class C motorhome that does not have permenant solar so I will be keeping the solar controller on the portable even though I have a Zamp Solar controller for the fixed panel on my WTW rig. I like the flexibility of leaving the controller on the portable even though you can wire directly to the fixed controller.


UPDATE: Because I could not find a 160w flexible panel for a reasonable price I have opted to go with a popular 120w Cynergy panel from Solar Blvd. at $139. If this proves to be to small I'll be able to add a second panel, have 240w on the roof and still cost less.