Open Circuit Voltage and panel wiring

[AlexanderKristiansen]

Hey! Lots of great threads on the subject of open-circuit voltage, but haven't found exactly what I am looking for.

I have a 24 voltage system. I am thinking about expanding my PV array and I am looking at two 345W panels with 41 Voc. I'm told that I should add 15% to the Voc because the voltage can rise in lower temperatures. That would bring two panels in series to about 94V. The manual of my inverter states that the "PV Array Voltage Range" is 30 - 80 Vdc. But the "Max. PV Array Open Circuit Voltage" is 100Vdc.

1. So what is the max. limit? 80 or 100Vdc. Will it be safe to put 2 x 41 Voc panels in series?

2. If I put the panels in parallel, will this affect the wiring size when the voltage drops from 82 to 41? Does panel voltage affect wiring size?

3. In many wiring size calculators, they ask for nominal system voltage? Is it the voltage of the inverter (12/24/48) or the voltage of the panels they need to know?

4. As I understand it, higher PV amps will result in a "clipping" and the only thing that happens is that you lose the Ah above the inverter limit. But what happens if you go above the inverter "Max. PV Array Open Circuit Voltage"? Will the inverter stop charging until the voltage drops or could I "fry" the inverter??

 

[snoobler]

1. Likely, but it depends on how cold it gets in your area. 82V vs. 100V is a pretty safe margin. 2S is likely fine.

2. Maybe. Yes. Lower PV voltage/higher current makes the voltage drop worse. In your scenario, the wiring losses will be 4X going to parallel from series (1/2 voltage; 2X current = 4X worse wiring losses).

3. Depends. For the Array to SCC wiring, you use Vmp and Isc. For the SCC to battery, you use battery voltage and charge current.

4. No. Higher PV POWER will result in clipping. You do not want to exceed the PV input limits. Period. If you go above "max pv array open circuit voltage," you kill your SCC.