How many Watts do I need

Discussion in 'Solar Power' started by stevec, Jul 8, 2014.

  1. stevec

    stevec Funster

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    Our first motorhome (Autocruise Starfire) and I want to fit solar power. Only the standard electrical items....lights (not LED)....water pump. Fridge will be on gas as will the water heater. At the moment we don't have a TV/DVD but do intend to get one. No hair dryers or straighteners and no inverter. We will need to charge phones /tablets and possibly look at how to run a laptop on DC but that is about for the forseeable future. Just how much solar panel wattage will be needed for three season running in the UK (long weekends mostly)? We plan to go to France for a couple of weeks in September also. I'm considering a 120W system and 10A controller (I have a cheap PWM sitting on a shelf from a prior domestic project) or at the other extreme a 250W panel (being sold by a local domestic solar installer) which is only a few pounds more than the 120W panel, and a 20A MPPT.

    If I go the expensive option I'd like to remove it when swapping MHs (as everyone says I will in a few years!). Is it easy to remove fixings stuck on with Sikaflex?
     
  2. Terry

    Terry Funster

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    Why not see how you go with what you have? then add a extra battery -- go down the solar route if that does not supply your needs -I suspect you want solar rather than need ;)
     
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  3. keith

    keith Funster

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    I have an Autocruise and fitted from new were 2 110ah leisure batteries which have proved to be enough for us with a very similar set up to what you are planning. We have 90W solar and except for the dark days of winter this has proved to be adequate.

    I have contemplated adding another panel but so far never had a problem with the current set up, so if it's working OK I'll wait and see.

    Fixed mine with Sikaflex so don't think I'll be trying to remove it any time in the future, I'd be fearful of damaging the roof.
     
  4. funflair

    funflair Funster Life Member

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    Hi

    Cant really fault what Terry says as two batteries should last you a long weekend without solar, but if you still want to go solar the 120watt should make you self sufficient for as long as you want to stay in one place in France as long as you get half reasonable bright days, does not need full sun, but I would say go for MPPT regulator as it will maximise whatever is there.

    The 250watt panel would be quite big so that would depend on your roof size/space and it would be heavier if you are watching Kg's

    Martin
     
  5. John Laidler

    John Laidler Funster

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    If it is mostly for long weekends a 120W system with two leisure batteries should be enough. We have a 100W system but with LED lights and seem to able to run more or less continually. The diesel Webasto heater takes the most current but that is mostly used in the winter on sites with EHU although of course it does heat the water at other times but isn't running continually then.

    I would also plan to leave it on the MH when you sell. The buyers will expect solar power these days.
     
  6. scotjimland

    scotjimland Funster Life Member

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    I'm with Terry on this .. add a battery then see how it goes..

    I can't really say if a solar panel is worth buying or not as I've never needed it.. a decent size battery bank and you should be able to last a week or more..

    our last RV had four x 85ah batteries and a genny for back up.. only ran it a few times in five years .. 3 years full time, during which we used free or low cost aires with no EHU

    but it all depends on your style of motorhoming and personal needs.
     
  7. funflair

    funflair Funster Life Member

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    The other advantage of solar is that it will keep everything topped up when you not using the van, again depending on your usage but this might be a big benefit if you don't use it for a few weeks.

    Unless of course you park it indoors like we do:doh:

    Martin
     
  8. Busman

    Busman Funster

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    I'll let you know how I get on fitted a 120w panel Sunday and am off for 4 nights/5 days camping to cardigan bay this weekend. I have a 110ah battery
    Dave
     
  9. stevec

    stevec Funster

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    The thing with an extra battery is finding somewhere to put it. The existing one (which is new) is in its own box set into the floor of the locker. I'd have to build a separate compartment (vented) in the same locker to accomodate another one. Unless someone has already done it in a 2006 Starfire and knows where it is best placed!
     
  10. Wildman

    Wildman Read Only Funster

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    the panel will charge one battery very quickly and have wasted power. If you add a second 110 amp/hr battery then you have a bit of leeway on a wet and cloudy day or two. It's no use producing a lot of amps if you cannot store them. simples.
    You need to do a full audit of max possible usage and count up the total amp/hrs required. Remember a panel will only produce a fraction of its stated output most of the day and most of the year. So store what you need (add extra batteries) and provide a means of replacing lost charge (Solar) or maybe a B2B charger will work for you.
    As to removing panels you will need to drill out the rivets and leave the brackets on the roof when removing panels.
     
    Last edited: Jul 8, 2014
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  11. simbadog

    simbadog Funster

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    I have a single 110ah leisure battery & a 100w panel on roof, using all LED lighting, 12v TV, fridge on gas & gas heating we appear to have ample power with the extra going to top up engine battery. (y)
     
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  12. JJ

    JJ Funster

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    Watts are like cold beers in the fridge...

    You can never have too many.


    JJ :cool:
     
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  13. Traveller_HA5_3DOM

    Traveller_HA5_3DOM Read Only Funster

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    I use a cheese wire to slice under the brackets. PU adhesive like sikaflex needs to be at least two mill. thick to have it's full strength, so it makes it easy to saw it with a cheese wire and a couple of wooden handles made from a few inches of broomstick.
     
  14. longdog

    longdog Funster

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    Just a though...... I have been thinking about solar panels, my local dealer said simply fit another 100 amp battery though.

    Doesn't the extra weight of an additional battery outweigh ( sorry ) the cost of a solar panel? I thought a solar panel would be better as it would keep the leisure battery and van battery topped up when not in use anyway?
     
  15. steevie

    steevie Funster

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    It doesnt sound like you need a lot of power compared to many, but I wouldnt be without a solar panel. It also keeps everything charged up when you stand the motorhome for long spells like over the winter. We got a domestic type 250 watt one about 3 years ago, and a £20 30amp controller from ebay, and used sikaflex. The whole lot cost £225, and has been great. To get the best from it though, you really need an inverter, then you can use all those things from home that make life away so much better.
     
  16. Gromett

    Gromett Funster

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    I have been fulltiming for over 5 years now and I now have a simple rule. More is better on both battery and Solar. But getting a balance is good.
    The limiting factor on solar is roof space and weight.
    The limiting factor on battery is space and weight.

    With those two things in mind. I would start with 1 decent battery and 1 x 80w solar panel.
    I now try to match watts for AH. ie if I have 110AH battery I will try to get around 100Watts solar.
    I am currently on 250 AH and 240 Watts. Last year I had 500AH and 240Watts and lasted almost 9 months off hookup with no generator usage.

    Neither battery nor solar will automatically make you self sufficient all they will do is extend the time between needing hookup or start your generator.

    Solar works best if you have good sunny weather and negates the need for large battery banks.
    Large battery banks are best for when the weather is miserable and you don't have access to EHU or Generator.

    A good combination means that when the sun shines you can fill up your batteries and a decent battery bank means that when the sun fades you have enough to keep you going for X days.
    The bigger the battery bank the bigger X becomes.

    I stick with 80 watt panels because they seem to give the most Watts per £ spent.

    One final thing, Get rid of the PWM and go with MPPT the difference is noticeable

    All this is just my opinion based on a fulltimers usage but I do have higher power demands than most due to my computer usage but I don't use an iron or hair dryer.
     
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  17. stevec

    stevec Funster

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    Thanks for all the comments. Very helpful. Looks like I may go for 120W and 10A MPPT. I can find a kit with all the bits to fit for about £220. It looks like panels go for about £1 per Watt. Certainly better than a few years ago.
     
  18. JJ

    JJ Funster

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    Gromett has it exactly right...


    Just consider your battery to be a water bottle. One bottle will give you lots of sips (LED lights) but very few big gulps (laptop charging, large screen tv etc. A hairdryer or microwave is like a big bath)

    If you have lots of bottles full of water you can last longer away from a tap.

    When you fill up your bottle(s) it will be slower to do so from a tap that just dribbles water out (solar on a dull day) than a fast flowing tap (EHU, solar on a sunny day, engine running or genny)

    Two dribbling taps will fill your bottle(s) twice as fast.

    Not much point, however, in having fast flowing taps (many/big panel(s) ) if you only have one little water bottle. It soon fills up and then the tap water just flows away and waters the world.

    I hope I am not being too patronising...

    (You do know what "patronising" means...) :rofl:


    JJ :cool:
     
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  19. martin

    martin Read Only Funster

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    Hi there I had 2 banner 100 amp leisure batteries fitted with a 150 watt solar panel have all led lighting , gas heating,gas fridge . Once my leisure batteries are full of charge it then trickle charges my engine battery especially good if I dont use the van for long periods of time also My old old 85 amp battery I can take with me when wild camping just to use a fan off using croc lead with 12 volt power end was going to get air con but takes too much power do have air con in the cab if I get to hot !!
     
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