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solar panels

thanks for your advice soler panels ect just one last question 2x120 watt solas 60feet batts to solas what size cable do i need thanks

Asked by: christopher smith  | 12.39pm, Monday 6 August

WW says:

The size of cable will affect the efficiency with which your solar panels will charge the batteries. This is because the current flowing through the cable resistance will produce a voltage drop. Voltage drop is the significant consideration in solar systems, rather than the current rating of a cable which is the maximum current that can safely be carried without the insulation melting.
Your two panels will produce a maximum of around 20 Amps, assuming your boat is wired for 12 Volts. If you use 16mm sq cable, at maximum output the loss in voltage will be 20%, less at lower powers. I would suggest that this is a good compromise between performance and cost of cable, and would not go below 10mm although bigger cable will reduce the loss. If you have a 24V system, the current is halved which reduces the voltage drop. The cable suggested will then operate at 10% loss, or smaller cables can be used for the same performance.
The cable used to meet the BSS requirements must be made from many strands of very thin copper wire, not the type used for high current AC installations in houses which typically have a few strands of quite thick wire. It is also important to fit a fuse close to where the solar system connects to the battery, in this case a 50A fuse will provide fault protection.

Rupert Smedley  | 7.59PM, Monday 6 August

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