Pre-installed solar panel cabling – how to check its capabilities?

[robdav]

Hi

 

I have a 2018 Pilote PVC that came pre-installed with a 120w semi flexible solar panel.

 

Is there any way I can check what the existing pre-wired cabling can handle power wise?

 

I’m looking to replace the existing flexible panel with a rigid panel with a higher wattage (175w as that is max roof space allows)

 

The charge controller can handle panels up to 250w but that wasn’t the one that came factory fitted.

 

Running new cabling would be difficult so I want to try and use the existing cabling.

 

Many thanks for any pointers.

 

Rob

 

[colin]

As I see it, you have two options, ask the manufacturer, or check the cable size.

[spirou]

If you happen to see any marking on the cable that's the easy way. Another option is measuring the diameter and calculating the surface area (or reference a wire size table). More than likely it's a 4mm2, less likely 6mm2. But in either case a 175W panel won't overload their capacity. In the somewhat unlikely case that it's less than 4mm2 (and long) then voltage drop might be an issue and rewiring might make sense.

 

Also, what are the Voc & Isc characteristics of the new panel?

[robdav]

Thanks Spirou

 

I will check tomorrow, weather permitting.

 

From memory the cable leaving the existing panel does not match the cable arriving at the charge controller. I will try and trace it tomorrow to understand the cable run.

 

EDIT - I've just checked and found where they've joined the panel cable to the internal wiring. The wiring going to the controller is 4mm2. The run must be about 3-4m max, possibly less.

 

They have also not fitted a cable gland entry box so assuming I can re-run the cable without messing up all the insulation then I may just do that.

 

What is the max 4mm2 will handle?

 

The Voc is 23.7 and Isc is 9.89.

 

I would like to go larger wattage but would then have to replace the charge controller as well.

 

Thanks again.

[mikefitz]

The existing 4mm2 cable will be OK. The volt drop at 10 amps with a 4 m run is about 0.33 volts, changing to 6mm2 cable would give a drop of 0.24 volts. In practice the panel current will be less than specified so in real life the volt drop will be lower.

Where volt drops are more important is in the cable run from controller to battery. Ideally the controller should be neat the battery with a short cable run, for 175 watts I suggest at least 6mm2 cable.

If the controller is PWM then the maximum charge current will be just under 10 amps, the panel spacified current. A MPPT controller will convert all the panel power with a maximum around 30% greater.

 

Mike

[Matrix Meanderer]

Good idea to replace the semi flexible panel. However, I would warn against taking it off the roof. My semi flexible panel burnt out in May due to overheating. After talking to the dealer and the panel supplier, the advice was, leave it in place, cut the cable and install the rigid panel over the top. Removing these stuck down panels is a "sod of a job" (dealer quote) and may damage the roof.

 

So good idea to replace the panel but leave it in place.