How big is big enough

Discussion in 'Solar Power' started by SomeoneElse, May 13, 2013.

  1. SomeoneElse

    SomeoneElse Funster

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    I'm sizing up things ready for our new van, but am very conscious of a possible weight issue. I have been looking at solar panels but am having difficulty finding any information on how much power they actually produce. By this I'm meaning how many Amp hours do panels produce in a day. I know days are longer in the summer and the elevation of the sun is higher, not to mention weather conditions, but I have no information on this what so ever so many empirical data from users would be extremely useful.

    I would like a system that would produce around 20Ah per day on most days, what size of panel will I need? I hoping the answer isn't measured in acres:Eek!:

    Also would it be advisable to have a dual controller in order to also charge up the engine battery. Something like this:
    http://www.futurlec.com/Dual_Battery_Solar_Charger.shtml

    I've never had a problem with my engine battery even when left unused for a couple of months in the winter, but the dual controller cost very little extra.

    Many thanks
    Gordon
     
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  2. Reallyretired

    Reallyretired Funster

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    The standard 100w panel that most use will produce 3A to 5A when the sun is shining, and about 0.5A when it's dull.
    This corresponds to 0.5-5Ah per hour so on an average day around 3Ah per day in winter if you're lucky, up to 30Ah a day in summer. They also work better the further south you are, so obviously a very wide range though perhaps marginally better than the length of a piece of string.
     
  3. Spacerunner

    Spacerunner Read Only Funster

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    When you get around to doing your calculations entirely rule out winter usage. You will definitely need a hook up if staying anywhere for more than a couple of days,
     
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  4. jonandshell

    jonandshell Funster

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    Nah!:BigGrin:

    Check out the Sterling Power website! Lots of stuff there to solve your winter power issues.:thumb:
     
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  5. vwalan

    vwalan Funster

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    i have 6x80wt panels and in winter in sp[ain and portugal .kept my 240v fridge running through inverter,240v twintub washing machine every two weeks . . plus computer occasionally .but lots of other things on 12v.we had no ehu from begining of nov and returned end april . my mate as 560wt and he manages as well . he lives in his fulltime .yes end sept /oct he does have a problem based in fort william .
    hope that gives you something to think over .
     
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  6. SomeoneElse

    SomeoneElse Funster

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    Yes its caused me a lot of thinking, but I'm have problems with the units:Sad: I think you are getting 95 socks washed per week per install kW of solar panels. Am I about right:thumb:
     
  7. vwalan

    vwalan Funster

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    think unless you have plenty you cant get enough power to be very useful.
    i had three panels for a few years but that wasnt enough .
    i have a bank of 600ah batteries and also use a 24v to 12v battery to battery charger. works like a 12v to 12v but my truck is 24v.
    its hard to say how much you get from a panel . in the ideal best day possible 5 amp is supposed the best you get per hour , but only for a short time if the panel is tracking the sun.
    in summer my system produces loads . on a sunny day .
    i was powering the fridge in the house on an extension lead but this rainy weather as set the inverter squealing only last night . takes a few days of good sunshine to put the batteries back up. cant talk figures as its so variable all depends on the weather.
    but big bank of panels and a big bank of batteries helps.
     
  8. Gromett

    Gromett Funster

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    I have long given up on trying to guess how many solar panels a person needs.
    No matter how many you need to survive in the summer it won't be enough in the winter.

    I now just consider solar panels as a range extender.

    If on a certain trip you could last for X days on batteries alone. 1 panel of Y size will give you an extra Z days but only if the sun shines :thumb:

    I hope that helps :Rofl1::Rofl1::Rofl1:.

    If you go away for fixed periods of time and don't drive during the holiday then extra batteries may be the best bet providing you are not talking about really long holidays. If however you drive every day then a B2B charger will be as good. On the other hand if you are going somewhere sunny and driving just a little then a Single 80 Watt solar panel will be great providing you aren't greedy with appliances. If you are greedy with appliances then a generator may be necessary. If you aren't greedy with appliances and have only reasonable sun then double up on both the batteries and the solar panels.

    If however you are going away for an extended period of time. Get solar panels, B2B, extra batteries and carry a generator. If your payload won't support this then you need a bigger van... Remember to check you driving license if you go above 3.5T though..

    I could go on but I think I made the point I was trying to.

    There are so many variables and with solar panels the weather adds an extra throw of the dice..:Wink:
     
  9. SomeoneElse

    SomeoneElse Funster

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    Reallyretired are these figures based on actual readings you have seen or are then from the literature from the makers/sellers?
    The 5A figure in high summer looks good because with a charging voltage of 14.4V thats 72W, not bad for a panel flat on the roof rather than face on to the sun.
     
  10. SomeoneElse

    SomeoneElse Funster

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    Ah! a twintub, not seen one for forty years, my parents gave us one soon after we married. Linda hated the thing and got rid of it after a respectful period and bought an automatic.

    Do you heat the water in it using electricity from your inverter or do you fill it with water heated by other means?
     
  11. SomeoneElse

    SomeoneElse Funster

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    Gromett, just to make it clear I wasn't asking anyone to design a system for me. I was however hoping that some Funsters with a battery monitor and a solar panel would share some of their observed readings with me.
     
  12. vwalan

    vwalan Funster

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    hi. its a plastic twintub . have a look on ebay . smaller than the old ones . i use the instantaneous water heater i have to heat the water.
    works great . the spinner is magic .
    http://www.ebay.co.uk/itm/PORTABLE-...VEL-MOTORHOME-WASHER-FREE-P-P-SPECIAL-OFFER-/
    mine is sort of like this different make but these work just as well .my mate uses one . mine is a sunncamp version.[ame="http://www.youtube.com/watch?v=cBpEMUd1dPE"]Sunncamp Twin Tub Camping / Caravan Washing Machine - YouTube[/ame]
     
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  13. oldun

    oldun Read Only Funster

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    A van is big enough when it is big enough for our own personal needs. This choice we need to make has no relevance to the needs of others.

    One of my major criteria is -"is the van small enough to allow me to travel to the places I wish to go."

    To me too large is just not acceptable.
     
  14. Gromett

    Gromett Funster

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    Ok sorry I misread what you wanted.

    I have seen 15 Amps off my 3 x 80 Watt panels last June with slight hazy clouds. This never lasted long though at that high level.

    I am currently getting 3 amps off a bright sun. However my batteries are not far off full so it could well be much higher. Last week I saw 7 Amps at around 9am.
     
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