sola panels

[mron]

hi
any idea what cable i use for solar panels to reg from reg to battery
cheers

 

[VicS]

Depends on the current and the length of the cable run.. if its a long run then it'll be heavier than you'd expect.

Applies to the cable from panel to regulator too.

Here's a calculator http://www.freesunpower.com/wire_calc.php
Note some calculators are based on total positive plus negative cable length. This one takes theat into account automatically

 

[mron]

its 90 watt panel at the moment producing 21.9 vts

 

[rogerthebodger]

I have used 2.5 sq mm but the solar to regulator is not as critical as regulator to battery, unless a MPPT regulator is being used, so best to position the regulator close to the battery.

 

[wotayottie]

as big as you can. your panel will struggle to produce much more than a fraction of its rated output and you dont want any of this wasted in heating up the wires to your batteries. So you want the lowest resistance you can manage and that means the thickest wire

 

[VicS]

its 90 watt panel at the moment producing 21.9 vts

Current in amps is what must be taken into account not volts .... 21.9 volts will be its open circuit volts ie measured at the panel when no current is being taken from it.

The manufacturers specification should give some data on the panel's performance . ie the voltage at which its maximum power output is obtained and the current to which that equates. The maximum , ie short circuit current may also be stated

However for a 90 watt panel take the maximum current at something like 5 amps

Go the calculator in my link

Step 1:- Enter 12 for the operating voltage

Step 2:- Enter 5 for the maximum current

Step 3:- Enter the distance in feet between the solar panel and the battery

Step 4:- Enter 3% as the acceptable voltage drop


You have not told us the distance between the panel and the battery
but suppose it is 20ft
The calculator then give you a wire size of 13 gauge ( that's 13 AWG)
13 AWG is approx 2.6 mm². Call that for practical purposes 2.5mm²

If the distance is 30 ft you will get 11 AWG which is approx 4 mm²

If the distance is only 10 ft you will get 16 AWG which is approx 1.5mm²


Now do it for the cable run length from panel to battery that you will have in you boat.
Use cable no thinner than the result for the wiring between the panel and the regulator and between the regulator and the battery

Do not forget to fuse the connection to the battery.