Cable voltage drop

gactrx · October 2014

Hi have change the position I will put my controller and it's now 26 meters from the PV array junction box. I have 16mm2 two core cable (about 5 AWG) for this. The rated current of the panels is 26 amps and VMP is 73.8 volts.
I'm not sure what figures to use for the voltage drop calculation to check on the distance and if it's ok. The controller is the Classic 150 and I'm charging a 24 volt battery bank. If I put the panels in the other configuration I have it's two strings of three panels which is marginal for voltage.
With the longer distance, will the panels in low light and therefore low voltage output not be as efficient as voltage drop increases
Thanks,

Alaska Man · October 2014

Re: Cable voltage drop

http://www.calculator.net/voltage-drop-calculator.html

gactrx · October 2014

Re: Cable voltage drop

Alaska Man wrote: »

http://www.calculator.net/voltage-drop-calculator.html

Thanks, I did try that but wasn't sure which figures to use. Is it correct to use the rated current and VMP voltage?
Is this acceptable:
Voltage drop: 1.39
Voltage drop percentage: 1.88%
Voltage at the end: 72.41
Is it borderline, great, or average?
Cheers,

gww1 · October 2014

Re: Cable voltage drop

g
That looks good to me. Most try for under 3% drop so at 1.8% you are doing very well.
gww

vtmaps · October 2014

Re: Cable voltage drop

gactrx wrote: »

With the longer distance, will the panels in low light and therefore low voltage output not be as efficient as voltage drop increases

The light level is irrelevant. The voltage is about the same at all light levels. It's the current that decreases with low light levels.

--vtMaps

gww1 · October 2014

Re: Cable voltage drop

Also at low current the wire should be even better. You losses are considered at the max current.
gww

gactrx · October 2014

Re: Cable voltage drop

Thanks very much, that sounds good.
Cheers.

Cable voltage drop

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