House grade solar panel - any use?

Discussion in 'Solar Power' started by treeman, Jan 25, 2012.

  1. treeman

    treeman Read Only Funster

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    I've been given a large solar panel that was destined for installation on a house roof but the glass has cracked on it so was being discarded. I've taped over the crack to hold glass and it works fine so was wondering if I could use it on my MH. Unfortunately it outputs 24v and is rated at 218w so plenty of power but too many volts.
    Is it easy to regulate the output to 12v is I suppose my question?
    Are there other problems using a panel designed for a house?
     
  2. Noggin

    Noggin Funster

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    Well, My tv has a voltage regulator which gives 12v with an input of between 11.5 & 25.5 (I think?)
    Some thing like that would do? Have a look at good old RS uk.rs-online.com

    :Smile:
     
  3. Reallyretired

    Reallyretired Funster

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    Although the panel is nominally 24v it could in use go as high as 50v. In the same way a 12v panel on a motorhome may well produce 25v in 'ideal' conditions. This is why you need a regulator.
    You can get 24v regulators that would work with your panel and then reduce the 24v regulated output to 12v, however as you say the glass is cracked and so it probably wouldn't last long out in the weather.
    You may find it cheaper in the long run just to buy a 12v panel.
     
  4. niggle

    niggle Banned - Rule 1

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    one of the m/h er's near me has done a dodgy deal and got two from the installers and fitted them to his m/h and they work better the the standard 12 volt ones it only cost him i think £39.00 for the box in maplins ??:Rofl1::Rofl1:
     
  5. treeman

    treeman Read Only Funster

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    Thanks for the replies. Looked at RS Components and they sell regulators down to 12v but prices are around the £100 to handle the wattage so as mentioned it may not be financially worthwhile.

    Niggle - do you know what product the m/homer bought from Maplin?
    Looked on Maplins but the only solar regulators I see are for 12v (max 20v) inputs. They do sell a handy 16A 12v regulator on there for £22 and has 2 battery output connections.

    I've been told if I cover half the panel up it will output only 12v - just going out to try that now (bit overkill but if it makes panel useable then possibly worth a try).
     
  6. niggle

    niggle Banned - Rule 1

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    not a clue as all i did was help him lift them on the roof, sorry :BigGrin: if i see him at yard i will ask but we only pass from time to time,, i know he got the sparky to do the wiring for him as it was diff for him ...
     
  7. treeman

    treeman Read Only Funster

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    Well that works - covered half the panel and got 12.2v out on this cloudy day.

    Could this be the answer, permanently cover 1/3 (so 2/3rds for use on cloudy days) then have a removable cover to take it down to 1/2 cover for sunny days. Then buy the 16a solar charge regulator from Maplins with dual charging outputs to leisure and vehicle battery for £22.

    £22 for in effect a 109w charging panel?

    Does that make sense or am I looking at it too simplistically?
     
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  8. hilldweller

    hilldweller Funster Life Member

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    Possibly the worst idea ever floated on FUN.

    Get on ebay and find a Solar Charge Controller with the right input voltage and 12V out. Sorted.

    Apart from it being damaged and will probably fail the first time you go over a bump or if not when water gets in.
     
  9. treeman

    treeman Read Only Funster

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    As a new member I apologise if I've offered the" worst idea ever floated on FUN", only trying to find an affordable power source for my MH.

    Is this the type of eBay item product you are talking about - 10A solar panel charge controller / regulator 12/24V for camper / caravan / boat

    http://www.ebay.co.uk/itm/10A-solar-panel-charge-controller-regulator-12-24V-camper-caravan-boat-/110805574281?pt=UK_Gadgets&hash=item19cc86e289

    I appreciate the panel is weak and leaky so the plan was to re-seal the whole unit if it was viable to use. No point in replacing glass then find out it's no use to me.
     
  10. Reallyretired

    Reallyretired Funster

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    The 12-24v regulators are not your whole answer as they are designed to output 24v from a 24v panel and 12v from a 12v one. The voltage is normally set automatically once you connect to your batteries (which you must always do first otherwise you can zap the controller.
    If you look at the spec for the controller you will normally see a figure for input overvoltage which is usually about 28v fora 12v setup. In other words it will probably work in weak sun but in bright sunlight will either cook the regulator or cause it to automaticaly shut down to protect the circuits.
    This may work if you cover part of the panel in bright sun, but a bit of a faff. It probably only needs a small part covering as partial shading rapidly brings down the output. As an example, on a bright January day my single 85w panel gave 0.6A but after cleaning off a modest deposit of seagull crap it gave 1.1A.
    As an aside I had 3 more panels fitted on Sunday and since then it has been uniformly overcast and wet. The maximum I had was 2.2A, but I am waiting for sunshine.:thumb:
     
  11. stcyr

    stcyr Funster

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    I had a cracked panel on a previous MH - I put a sheet of perspex over it, trimmed to size and sealed - new owner reports it still works fine. :thumb:
     
  12. hilldweller

    hilldweller Funster Life Member

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    Well, electrically that was like taking 4 plugs out of a V8 because you want a 4 cylinder.

    That controller is very close 50V in 12V out but only 170W. The chances of getting more than 170W is slim because the rated output is for best possible conditions. You can take a cheap gamble or go for a bit bigger regulator.

    But if that cracked glass flexes and splits one of the cells you've had it because they are wired like "fairy lights" and probably half would go down with just one cell.
     
  13. Reallyretired

    Reallyretired Funster

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    As another aside, a 10A regulator is only enough for panels up to 120w max. You should be looking for a 20-30A regulator.
     
  14. hilldweller

    hilldweller Funster Life Member

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    Don't confuse him even more.

    The regulator he has chosen will take any input up to 50V.

    The regulator will determine if it is charging a 12V or 24V battery and switch automatically.

    That is it, simple.
     
  15. Reallyretired

    Reallyretired Funster

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    Don't worry about comments about the 'worst idea' floated on the forum. Hildweller is exaggerating, there have been many worse. I'm sure some of mine have been .

    BTW how heavy is your panel, I assume as it is for a house the manufacturers may have not bothered much about keeping the weight down.
     
  16. treeman

    treeman Read Only Funster

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    Panel is rather heavy, could cause a few issues in mounting and directing at the sun.

    Panel spec has max open circuit voltage (Voc) of 33.6v at 8.4amp so if a controller could handle 50v and 20amp I'd hope that would cope. It is all a tad confusing regarding all the electrical technology but seems a shame to waste a powerful panel so I'll pursue it.

    It would be nice to have some sun so I could check max voltage before spending on a controller.
     
  17. hilldweller

    hilldweller Funster Life Member

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    That is the downside of the way panels are mounted on a MH, usually flat. The panel spec is for it face the sun, here at 50 deg a flat panel loses 25% ( sin(50) = 0.75 ). But if you angle it at 50 deg you have to arrange for it to track the sun.

    We came to the conclusion a while ago that it's simpler to throw on another panel than have a tracking system.
     
  18. stcyr

    stcyr Funster

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    Is this any help? : "Almost any charge controller will work as long as the input voltage is rated to handle the open circuit voltage of the panel which may be in the 40v range. The panel's voltage will drop to match the load during charging, it just won't be as efficient as it could be unless you get a controller with 'maximum power point tracking' (MPPT). Mppt will get the most power from the panel and convert it to the proper charging voltage for the battery bank"


    :thumb:
     
  19. Wildman

    Wildman Read Only Funster

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    you could always add a second battery in series and charge as 24V then tap power for the van across one battery at 12V, however those glas panels are rather heavy and as already said very likely to fail due to flexing damage. I could use it as I have 24v system on my generator at the smallholding should you decide not to use it. Good luck.
     
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  20. CHRI$

    CHRI$ Funster

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    get the charge controler,and get it on the roof of the motorhome,welldone on getting it free of charge:thumb:value with cracked glass about £200 fix the glass and the value goes up:thumb:
     
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