Today I noticed one of the PV cables going into my 5kw Sunsynk was a bit loose. Seems the MC4 connector cracked where it attached to the inverter casing, and have asked my installed to remedy. However… while looking at it, I was a bit surprised to see how thin and whispy the cable on the inverter’s side of the connector was.  My own cable from the PV joiner box is a solid 10mm2 PV cable. But the one inside the inverter is way smaller.  This is how they come set up by Sunsynk, so presumably should be fine. 

Just a bit concerning as it looks a bit weak & undersized to me.  Or am I being overly concerned? 🧐

See pics below…

@Backbone Energy

The thick cable to the panels is only to minimise voltage drop.  You only need 1.5mm² cable for the current capacity.

9 hours ago, JAvandermerwe said:

Today I noticed one of the PV cables going into my 5kw Sunsynk was a bit loose. Seems the MC4 connector cracked where it attached to the inverter casing, and have asked my installed to remedy. However… while looking at it, I was a bit surprised to see how thin and whispy the cable on the inverter’s side of the connector was.  My own cable from the PV joiner box is a solid 10mm2 PV cable. But the one inside the inverter is way smaller.  This is how they come set up by Sunsynk, so presumably should be fine. 

Just a bit concerning as it looks a bit weak & undersized to me.  Or am I being overly concerned? 🧐

See pics below…

@Backbone Energy

The better question is why would there be MC4 connectors between the DC combiner box and the inverter. Almost as if someone got the cable length wrong and this was the solution. 

In any event, 10mm2 Pv cable is way oversized, you could have gone with 4mm2, these are a lot easier to install and cost a lot less. The voltage loss difference between 10mm2 and 4mm2 will be so small (on the Volts that you are likely pushing through the cable) that it won't make any difference. You are probably picking up a larger loss due to those MC4 connectors at the inverter that you are effectively negating the use of the 10mm2 cable.

Or is that how the 5kw is manufactured (or at least was at one point in time)

Edited March 28, 20231 yr by I84RiS

Thanks for the feedback.

The 5kw Sunsynk comes with those MC4 connectors - see the manual screenshot below. They then have those thin wires inside the inverter connecting to a white “box” in the inverter.  Not sure that box is, but will take a better picture of the part when I get home. 

I realise 10mm2 is oversized, but it doesn’t bother me. It’s only the short run between the combined box and the inverter that’s 10mm2 as I had them available at the time. The cabling from panels to combiner is 4mm2. 

On 2023/03/28 at 11:59 AM, JustinSchoeman said:

The thick cable to the panels is only to minimise voltage drop.  You only need 1.5mm² cable for the current capacity.

Thanks, I think you’ve confirmed what I was hoping to hear 🙂