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Thread: Solar cable

  1. #1
    pessimist is offline Registered User
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    Default Solar cable

    Am about to install a new solar panel rated at 80w so I guess I'm looking at 4-5 amps at best.

    The panel will require a cable run of ~10m to the batteries.

    Do I need special solar cable for this installation? The table I found suggests that I would need AWG 11 for this purpose. This apparently equates to 2.5mm or 4mm squared. Plenty of suppliers on fleabay but its not clear whether they are sizing in mm or mm squared.

    My brain hurts. Help.

    Thanks,

    Colin
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  2. #2
    VicS is offline Registered User
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    10 metres distance = total cable run of +ve plus -ve of 20 m

    20m = 66 ft

    from this table http://www.engineeringtoolbox.com/am...uge-d_730.html

    AWG 10 will result in no more than 3% volts drop at 5 amps

    AWG 10 is 5.26 mm˛

    use the next available larger size

  3. #3
    nigelmercier's Avatar
    nigelmercier is online now Registered User
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    Quote Originally Posted by pessimist View Post
    Am about to install a new solar panel rated at 80w so I guess I'm looking at 4-5 amps at best... 10m ...
    http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

    Says 6mm˛ so agrees with Vic.
    Nigel
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    my solar panel take volts out of my battreys and probley charg the the sun back up ?

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    To be honest the internal resistance of a solar panel is so high that the resistance of the cable connecting it to the battery should not be an overwhelming consideration. So I don't think you need to stick to the 3% drop rule - you should be fine going up to nearer 10%. I think 2 sq mm would be fine for the task.

    It is more normal to quote in sq mm than diameter - and you should also be able to tell by the price

  6. #6
    VicS is offline Registered User
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    Quote Originally Posted by watermint View Post
    my solar panel take volts out of my battreys and probley charg the the sun back up ?
    If its discharging the battery at night it is probably because it does not have a blocking diode.
    Solar panels supplied for battery charging usually have diode built in somewhere but it should be stated in the spec.

    If its discharging when the sun is shining its either defective or possibly connected the wrong way round (??)

  7. #7
    VicS is offline Registered User
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    Quote Originally Posted by bedouin View Post
    To be honest the internal resistance of a solar panel is so high that the resistance of the cable connecting it to the battery should not be an overwhelming consideration. So I don't think you need to stick to the 3% drop rule - you should be fine going up to nearer 10%. I think 2 sq mm would be fine for the task.

    It is more normal to quote in sq mm than diameter - and you should also be able to tell by the price
    True the panel resistance is high but you dont want to loose 1.2 volts in the wiring.

  8. #8
    pessimist is offline Registered User
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    Thanks everyone. Do I have to use "solar" cable which appears to be double insulated etc. or can I use any cable of the correct rating?
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  9. #9
    VicMallows is offline Registered User
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    Quote Originally Posted by pessimist View Post
    Thanks everyone. Do I have to use "solar" cable which appears to be double insulated etc. or can I use any cable of the correct rating?
    Of course you don't need to use 'special' cable ... or 'special' connectors for that matter. (I trust you are not just taking the micky ).

  10. #10
    VicS is offline Registered User
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    Quote Originally Posted by pessimist View Post
    Thanks everyone. Do I have to use "solar" cable which appears to be double insulated etc. or can I use any cable of the correct rating?
    You'd use twin flex surely unless you were running single wires in some form of conduit or trunking.

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