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Thread: Solar Panel and Battery

  1. #1

    Default Solar Panel and Battery

    I am getting a camper from ATC and am debating having them do the solar and aux battery. I know it would be less expensive to do it myself, but having them do it, means less chance of me screwing it up.

    I will be running an Engel and LED lights. The panel is 80 watts and the battery is 75 ah.

    I know the amount of sunlight is the missing factor here, but generally, would these be adequate? Thanks for your help.

  2. #2
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    Solar rules of thumb...

    PV modules (solar panels) will on average put out 80% of their nameplate rating.

    (They put out less when hot and more when cold. Since they are dark and pointed at the sun, they are usually hot.)

    Flat mounted PV modules will on average get a decent harvest for about 4 hours per day.

    (IF you park in full direct sunlight. Anything less than full direct (NO SHADE AT ALL) sunlight on the PV module and your harvest will be basically nothing. Even just a touch of shade on one corner can cut the module output by 1/3 or 1/2 off the top.)

    So you can figure on average 80w x .8 x 4 = 256 watt*hours per day harvest.

    Then, the charge controller (between the PV and the battery) will not be 100% efficient so you'll lose a few watts there, and the battery will only be about 80% efficient. Let's ignore the loss from the charge controller and just figure the battery. So 256wh x .8 = 204.8.

    So you can figure on average that you'll end up with about 200 watt*hours per day actually getting into your battery and being available for use.

    Not including recharging from the vehicle engine or a generator, your "solar only" power budget is 200wh/day.

    Now you need to figure out how many watts your loads draw, and for how many hours per day and you can compare that to your power budget.

    Say your fridge draws 30w when the compressor is running, and it runs at a 30% duty cycle (20 minutes out of every hour). That would be 30w x 8 hours of run time for a total of 240wh per day. That would exceed your "solar only" power budget.


    An 80w panel isn't very big. If you rigged it with an extension cord and manually deployed it (leaned it on a nearby rock) facing the sun and moved it a couple of times a day, you could park in the shade and also get double or triple the harvest.
    ...
    ...
    Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
    Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker

  3. #3
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    I wanted to do all the calculations but I had the 55W Siemens panel, Costco battery, and Waeco CF-50 fridge with a blanky. Here is my real world findings - I can run my fridge full of 30 beer in the summer in Mexico without starting my vehicle for days. Your mileage my vary
    "Knowledge without experience is just information"--Mark Twain

  4. #4
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    Default Never enough

    Take it from me. You will never have enough. I know, I know, what a stupid comment. What I mean is there is noway of seeing into your future as you get used to your new way of camping.
    At least have the camper wired. I am pretty sure they come that way anyways. That way when you have the money to do the best panel and charge controller, you can do it right.
    If you do calcs for just the fridge and lights, you will bring chargers for phones and other items, you might bring a radio and on and on.
    What I am saying is that there is nothing wrong with doing it later and it is very easy. There are a lot of people here, and DWH is one of them, that knows a lot about solar. I can always take pictures of my install and send them to you.
    Hope this helps.
    Jeff
    Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!"
    Hunter S. Thompson

    2010 Tacoma DC 4x4 lb
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    2003 4RUNNER V8,
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    Heart attack survivor 2/23/2011

  5. #5
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    We have I think (came with camper!) two 100W panels and 2x 255Ah AGMs. Northern Scotland in winter the panels may as well have not been there! The French Med coast in summer the panels alone kept the batteries full despite halogen lights, Eberspacher for hot water, water pump for two showers a day and compressor front opening fridge, 37deg C max

    Links to a UK campervan site for more opinions! Do US campervans go for solar much? UK campers like solar so when they visit France where you can legally park up anywhere they can be independant.

    http://www.motorhomefacts.com/ftopic...t=diy&start=20

    And a thread regarding if making a tilting bracket to follow the sun is worthwhile, from where the attached table comes from

    http://www.motorhomefacts.com/ftopic...solar&start=40

    Edit Having read the above post, yes, even twice what we have would be cool. You know Series III Landys had a Safari roof? Our whole camper roof covered with a seperate layer of solar, with an inch gap to keep the inside cooler might be enough
    Attached Images Attached Images
    Last edited by grizzlyj; 12-31-2010 at 03:41 PM.

  6. #6
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    Quote Originally Posted by LandCruiserPhil View Post
    I wanted to do all the calculations but I had the 55W Siemens panel, Costco battery, and Waeco CF-50 fridge with a blanky. Here is my real world findings - I can run my fridge full of 30 beer in the summer in Mexico without starting my vehicle for days. Your mileage my vary
    Yea, but the question is, how long could you do it without the solar panel?

    Probably about the same.

    For a small solar setup, the best that usually happens is that the PV just stretches out the time until the battery is dead. If your battery could run the fridge for say 5 days, with the solar now maybe it can go 6...

    Look at my example above - taking out 240wh/day and putting back 200wh with the PV. The battery is going down by 40wh/day. That's called "deficit charging" - when you recharge, but not all the way.

    Of course, I have no idea what your fridge draws or what duty cycle it runs at. It's entirely possible that your 55w panel in good sun harvests more than the fridge draws.
    Last edited by dwh; 12-31-2010 at 03:47 PM.
    ...
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    Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
    Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker

  7. #7
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    Quote Originally Posted by dwh View Post
    Yea, but the question is, how long could you do it without the solar panel?

    Probably about the same.

    For a small solar setup, the best that usually happens is that the PV just stretches out the time until the battery is dead. If your battery could run the fridge for say 5 days, with the solar now maybe it can go 6...
    Not my experience at all prior to installation of the panel. Battery would be good for about a 1-1 days max with summer time temps, from the limited testing I have done. Depending on the time of day battery was metered I would still see 12v after a couple days with my solar set up.

    Keep in mind Im in an area with some of the longest days and highest solar insolation (2500btu/ft) in the world. My panel is mounted flat on the roof with an 1" of air space.
    "Knowledge without experience is just information"--Mark Twain

  8. #8
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    www.caravanandmotorhomebooks.com/
    There are some good value articles here too.....

    Cheers,
    Peter
    Note that we have a non commercial relationship with Collyn.
    ......................Enjoy.....................
    OKA196, 4x4, DIY, self-contained motorhome. http://www.oka4wd.com/xt196.htm

  9. #9
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    Adventure Trailers has a page on all of the calculations.
    http://www.adventuretrailers.com/pag...t_calculation/

    The main improvement nowadays is the new-fangled Maximum Power Point Transfer (MPPT) solar charge controllers. In really good sunlight they have a smaller advantage but start to offer gains in less than optimum conditions. Cost is the bad side and prices are barely coming down now.
    Jim
    4x4 Tourist


    Trip reports are on my Blog: "Sun To The North"

    Two Favorite Expo Quotes: "A bad day on the trail is better than a good day in the city" & "Bad days make for GREAT stories!"

  10. #10
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    Noosa Australia
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    PV modules (solar panels) will on average put out 80% of their nameplate rating.

    (They put out less when hot and more when cold. Since they are dark and pointed at the sun, they are usually hot.)
    If you're interested >>> http://www.expeditionportal.com/foru...ad.php?t=24917
    Last edited by whatcharterboat; 01-01-2011 at 04:56 AM.

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