Flat solar panels vs Angled





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  1. #1
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    Default Flat solar panels vs Angled

    Has anyone done any tests of solar panels lying flat vs angled at approximately 30 deg to the sun.

    Do you have any test results of how it affects the charging rate etc.

    The reason for my asking is that I want to build a trailer I want to know if it will charge sufficiently while travelling in the daytime to run the fridge for instance.

    I know that solar panels need to be directed at the sun and have done some solar installs but never tried this.
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  2. #2
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    Default Re: Flat solar panels vs Angled

    I have 2x65W panels on the roof of my camper. When travelling they are horizontal and provide plenty of charge for 40l NL running as a fridge @2 deg, plus LED lighting.
    I very seldom use the alternator unless there is heavy cloud or rain.
    I have traveled over 15 000km with this setup and never once had a problem.
    Btw I replaced the NL intelligent charger with a Victron battery combiner and have an override switch in the negative connection.
    With the NL unit I found the vehicle battery was being overcharged when the solar regulator was boosting the deep cycle battery.
    I have a Microcare MPPT regulator.
    My2cw
    Last edited by BMC; 2016/05/07 at 09:59 AM. Reason: correct name/type of solar regulator
    Brian Coleman
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  3. #3
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    Default Re: Flat solar panels vs Angled

    My idea is to not have to setup the panels and leave them as they are flat or slightly angled depending on installation position, so this answers most of my questions, it obviously just means that if you do want to charge from the vehicle because of the weather for instance one would need to do the connection when required.

    I believe a good charge controller is well worth it's money because of charge rate etc.
    Last edited by bokvirsports; 2016/05/01 at 05:38 PM.
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    Default Re: Flat solar panels vs Angled

    If you track the sun, vs angle fixed you gain about 20%, so I guess you can loose about 20% when flat.
    Last edited by JLK; 2016/05/01 at 06:34 PM.
    Johan Kriel

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    Default Re: Flat solar panels vs Angled

    Tracking the sun can perhaps gain more than 20%, but on a vehicle, it is impractical to have tilt. If so, in which direction? So keep them flat and use as the largest panel(s) and best controller you can afford and live with it.

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    Default Re: Flat solar panels vs Angled

    I fitted 2 x 150W modules horizontally coupled to two 120ah batteries on my trailer.

    By 10h00 last Monday at the GTG my batteries were at 100% charge running a Snomaster 85l and quite a few LED lights during the night.

    Rather oversize on your modules and batteries than worry about tilting them all day.

    Unless you have very uncomfortable camping chairs!

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  7. #7
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    Default Re: Flat solar panels vs Angled

    Unless you have very uncomfortable camping chairs![/QUOTE]

    That will give a reason to get up even if it isn't to get a cold one

    I have been experimenting at a solar install I am busy with, where I have 4 panels angled and 2 flat and I cannot see a major difference in charging at the most I see 10% difference.

    What does make a huge diffence is having the correct size cabling for amps which causes a bottleneck. Just on cabling I gained 25% by doubling from 6mm sq to double that and I am intending replacing the cabling with 25mm sq which would then be optimum
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  8. #8
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    Default Re: Flat solar panels vs Angled

    Quote Originally Posted by bokvirsports View Post
    Unless you have very uncomfortable camping chairs!
    That will give a reason to get up even if it isn't to get a cold one

    I have been experimenting at a solar install I am busy with, where I have 4 panels angled and 2 flat and I cannot see a major difference in charging at the most I see 10% difference.

    What does make a huge diffence is having the correct size cabling for amps which causes a bottleneck. Just on cabling I gained 25% by doubling from 6mm sq to double that and I am intending replacing the cabling with 25mm sq which would then be optimum[/QUOTE]

    If I may. And please this is honest advise.

    Do a complete rethink and new measurements and a redesign of the system architecture.

    I have never seen or heard of or even know of 25 mm in a solar installation. Not even in an installation with a 100 panels.

    If you need to go above 6mm then you need to change the system design to operate off higher primary DC Voltages.
    Cheers

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  9. #9
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    Default Re: Flat solar panels vs Angled

    I have been fighting this myself with the supplier telling him his panels are rubbish etc. Long story short I was convinced by a solar installer, who worked for telkom on their towers for many years that under my current 24v configuration I would get better results if I changed my cabling from the current 6mm sq to at least 16mm, hence the reason I added a set of wires for testing and I definitely got an increase of at least 6amps higher to my controller.

    So to stop buggering around I decided to install 25mm sq today which is inexpensive compared to installing 2 extra panels and this should remove my current bottleneck altogether.
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  10. #10
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    Default Re: Flat solar panels vs Angled

    Quote Originally Posted by bokvirsports View Post
    I have been fighting this myself with the supplier telling him his panels are rubbish etc. Long story short I was convinced by a solar installer, who worked for telkom on their towers for many years that under my current 24v configuration I would get better results if I changed my cabling from the current 6mm sq to at least 16mm, hence the reason I added a set of wires for testing and I definitely got an increase of at least 6amps higher to my controller.

    So to stop buggering around I decided to install 25mm sq today which is inexpensive compared to installing 2 extra panels and this should remove my current bottleneck altogether.
    The numbers just don't add up to me. The part that scares me is the "at least 6AMPS higher to the controller" Sub optimal cables will manifest itself as a lower Voltage into the cable with a consequent lower total Power output. Depending on the type of controller, the cables would need to be severely undersized to make such a difference in current into the controller.

    Maybe if you explain the type of panels (eg Power and Voltage Voc and Vmp Imp) and the length of cable runs.

    You may be way better off with the panels in series and a decent high voltage MPPT controller.
    Cheers

    ZS5KAD
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  11. #11
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    Default Re: Flat solar panels vs Angled

    You may be way better off with the panels in series and a decent high voltage MPPT controller.[/QUOTE]

    The system is installed as a 24v cnfiguration with a 24v/50A controller PWM in this case.

    The inverter is 24v etc etc.

    Changing all this now for a controller that is first of all 3 or 4x the price or changing the whole setup to 48v is going to have a negative impact on finances for the customer in major terms.

    The reasoning behind the amps I didn't want to believe until I tested it myself, see it as the following.

    A solar panel has the manufactured cable which can handle it's own load then you start adding panels and suddenly the amount of amps and volts that has to travel through this cabling is not sufficient, just like a suburb road linking with a highway with more than one lane.

    My panels cannot be linked in series as they will exceed the voltage rating that the controller can handle. currently I can still ad more panels up to at least 8 in total at a major push.

    My VOC is 37.8 if I remember correctly and the amps 8.89.

    My panels are giving early morning volts open circuit around 32.5v each.
    Current config I am getting with 6 panels in parallel 2 flat and 2 angled a total of approximately 24 -28 amps mid morning and volts of 26 - 29 depending on the sun. I have not yet done the cabling properly but was running very similar volts but lower amps before adding the extra cable for testing.
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  12. #12
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    Default Re: Flat solar panels vs Angled

    Quote Originally Posted by bokvirsports View Post
    You may be way better off with the panels in series and a decent high voltage MPPT controller.


    A solar panel has the manufactured cable which can handle it's own load then you start adding panels and suddenly the amount of amps and volts that has to travel through this cabling is not sufficient, just like a suburb road linking with a highway with more than one lane.

    [/QUOTE]

    A combiner box near the panels, perhaps?
    Then proper spec cable to controller
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