Part 3 of my Solar Panel Testing

Discussion in 'Water Fed Pole Cleaning' started by mark m, Oct 13, 2015.

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  1. mark m

    mark m Hero
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  2. spruce

    spruce Grand Master
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    #2 spruce, Oct 13, 2015
    Last edited: Oct 13, 2015
    Mark,

    please may I ask what solar panel have you got?
     
  3. spruce

    spruce Grand Master
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    #3 spruce, Oct 15, 2015
    Last edited: Oct 15, 2015
    I'm looking forward to the results of Mark's experiment TBH.

    There are mixed reports from those who have them on their motor homes for anything other than keeping the batteries full charged whilst the van is laid up during winter.

    In fact there is a supplier and fitter of motor home components down in Cornwall that openly says on the motor home forums that they are a waste of time even although his company supplies and fits them. However, Mark has been able to fully charge his battery over the weekend, and this interests me.

    The issue in the UK is that the winter sun is very low on the horizon, so ideally the panels would need to be south facing and tilted at 78 degrees to work at their most efficient. Having them flat on the roof is the only way when driving but its not practical for our application to have a tilting system as some motor home users have done.

    For the experience and recommendations of motor home owners, the consensus seems to point toward 2 x 80 amp monocrystaline panels (they appear to be more efficient) for those who use their vans over the winter. Summer time isn't a problem but UK winter with limited sun is the issue, and this is the time we use more power, especially if Mark wants a run a low energy heater such as a tube heater.

    I copied this from a caravan owner's forum.

    Basic electrical formulas suggest that to produce 2000W from a 12V source would need 2000W/12V = 166A.

    That suggests that an 110Ah battery would be fully depleted in about 35 to 40 Minutes.
    To run this heater you would of course need a 2000W 12Vdc to 230Vac inverter, which will also use a little power of its own.

    BUT, there are a number limiting factors that might reduce that time further.
    A standard battery charger will only charge a leisure battery to between 85 to 90% of its full capacity. So at best your 110Ah battery will only have about 95 to 100Ah.

    As batteries age, their capacity is also reduced.

    Also leisure batteries do have a limited maximum current draw so you would need to check the batteries specification to see if its capable of supplying 166A.

    Further, most inverters have a battery protection system so if the batteries terminal voltage fall below a threshold it turns off. It’s quite possible the battery may still have 20 to 30Ah charge remaining, but is unavailable to the inverter.

    So all in all you may get 20 Minutes from a caravan charged battery.


    I also see that Mark is using a cheap (no disrespect intended) controller readily available from Ebay. It looks like it could be this:

    http://www.ebay.co.uk/itm/UK-STOCK-...o-Switch-TK-/331417174315?hash=item4d2a00c12b

    Mark would be much better off with a more expensive, genuine MPPT controller. I see there is a seller describing the same PWM controller as an MPPT controller which I wouldn't trust.

    http://www.ebay.co.uk/itm/10A-MPPT-...o-Switch-BG-/121388015386?hash=item1c434a1f1a

    A check on Youtube will show quite a number of different electronics experts showing that many of these controllers are fakes.
    Part 1

    Part 2


    This is why a MPPT controller is better.


    (If you aren't interested in this then my South African buddy's video clip is very boring - but for those who are there is a wealth of information that can be carried over to wfp.) Thanks for the video Martin.

    These are genuine MPPT controllers:
    http://www.ebay.co.uk/itm/301493530633?_trksid=p2060353.m1438.l2649&var=600419059368&ssPageName=STRK:MEBIDX:IT

    These Victron controllers can also be used in conjunction with a VSR (Volt sensing Relay), so you will still get the additional benefit of alternator charging when driving.

    I still think though that the best off grid heater for our application is a Propex gas heater with a frost stat thermostat.




     
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  4. Diwrnach

    Diwrnach Grand Master
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    Hope you do a course before even considering cleaning them!
     
  5. mark m

    mark m Hero
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    Hi Spruce I think I mentoned it on my first video I got the solar panel from a car boot it gererates approx. 22v and can be brought from maplins that is why I got a inverter so I don't burn out the battery , I will be testing a heater this weekend just in case in runs battery out and I cant go to work next day lol .The caravan clubs would know more than me so it looks like it wont work which is a shame .As for the controllers I have loads of controllers from suppliers some very expensive ones and diy ones which people have asked me to test out n but I am trying this one out for 6 months for a company at the moment and it is working very well
     
  6. spruce

    spruce Grand Master
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    Hi Mark,

    There should be a label on the back of the panel with specs which will be quoted in watts. Most of these panels have an 'open circuit voltage' of around 21 to 23vdc. Yours was showing 21.8v, but if its only charging your battery at 0.5 amps then its going to take a long time to fully charge that battery. But if its charging at 5 amps then it will be quicker. The bigger the panel the higher the watt output. Its like a car's alternator. They are all 12 volt but different alternators produce a higher output ie 60 amp, 90 amps etc.

    Yours managed to charge your battery fully over the weekend which is good. Where solar goes a bit pear shaped is in winter. I found a Met Office average sunshine report for the North East. NewCastle averages 50 hours of sunshine during December and 55 hours in January (compared to 175 average per month in May, June and July).

    According to a solar calculator
    http://www.batterystuff.com/kb/tools/solar-calculator.html
    I would need 2 x 130 watt panels on the roof of my van to replenish the 20 amps my pumps took out that day (based on Shurflo pump using 5amps per hour and working for 4 hours and 2 hours of direct sunshine per charging day.) I presume the calculation is made when considering the panel is located in the best position and tilted at the right angle for our latitude.

    Perhaps this is the reason why the owner of Vanbitz says they are a waste of time as ours would be fixed in the flat position as they would be on the majority of motor homes.
     
  7. mark m

    mark m Hero
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    Maybe for a caravan it is no good but if it can charge up a back pack or trolley as we work all day it could have it`s advantages
     
  8. mark m

    mark m Hero
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    Like you say in the winter I might find it is not good enough but I am thinking a good battery should easily last me the day at work so while i am driving around and before and after work it should top its self up
     
  9. spruce

    spruce Grand Master
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