Exceeding maximum input voltage on my Charge Controller?

Riley · December 2022

Hi Folks - I am looking at adding more solar panels to my roof top array.
My charge controller is a Schneider Conext MPPT 60 150. It has a maximum input voltage of 150VDC.

My current solar array (3 parallel strings of 4 panels in series) has an open circuit voltage of exactly 150V (Voc = 37.5VDC so 37.5 x 4 = 150VDC). However when I look at newer panels, their Voc is always a few volts higher (ex: 40.15) so I would be getting 160.6 VDC at the CC input.

I can't find any panels with lower Voc and so I am thinking I need to rewire my array to have 3 panels in series instead of 4 in order to keep below the 150VDC. I really don't want to blow up my CC so am I right to rewire and drop down? Also don't want the additional cost of a new CC (or additional PV wires from my roof top).

Second question: It's possible that with my additional panels and my battery bank voltage of 48V, I could have more than 60A on a good day. The maximum output of the charge controller is 60A. I would think the charge controller would be smart enough to ensure the output current isn't exceeded (limits the current to 60A). I don't care if a waste a bit of power but do I need to worry about the maximum output current in terms of the charge controller circuitry?

Since the controller also has a setting to limit the max charge to the battery bank (expressed as a % of the battery bank capacity), I assume I could just dial the max charge rate down...

Vic · December 2022

Hi Riley,

Simply, you do not want to ever exceed the maximum PV input voltage spec for any CC, EVER.

From what I read in the specs for the 150-60 SCC, implies that it ceases operation when this input voltage exceeds 140 V DC, and that the chance for SCC destruction begins at 150 V DC. So, in cold WX you would probably see the SCC, sleeeping/resting uncer cold WX, if your push this input V with strings of four PVs.

From the manual:

Electrical Specifications: "... Maximum PV Array Voltage (Operating) 140 VDC Maximum PV Array Open Circuit Voltage 150 VDC ..."

The max Voc from the PVs needs to be adjusted for temperature. The colder are the PVs, the higher is this Voc.

This max V, is a hard limit what needs to never be exceeded, and needs some safety margin.

Just do not chance it. Highest Voc ever seen, is recorded in non-volitle memory, and will VOID any warranty.

FWIW, IMO, etc, Vic

Riley · December 2022

Yeah, after lots of reading and talking to others, I realize that I currently have a design issue. Right now with my current configuration of 4 panels in series, I am right at the edge of exceeding the max 150VDC. The system is 6 years old and I guess I have been lucky up till now.
This spring's project is to rewire into series strings of 3 panels and add 6 or 9 more panels in the same fashion. with 9 more panels (7 strings of 3 in series), I start to push the max 60A of the controller and the wiring but maybe I can protect it with a 60A breaker. (short circuit current would be 63A and the Imp would be 60.5A).

BTW - I am assuming I have 4 wired in series as that's what the installer/designer told me 7 years ago when buying the system and the combiner box used in a 3 position box. That will need to changed out.

Exceeding maximum input voltage on my Charge Controller?

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