Good Day...i found this forum very help full..i have a great concern on inverter photovoltaic power intake . I have  learnt that Open Circuit Voltage (VOC) is something to be seriously when  installing panels and it should not be exceeded nor played nearer

My main concern is on current generated by panels, what really  happens if we exceed the rated one inverter.  NOTE that this confusion came after i read somewhere where it said the inveter only cares much about the VOC and only take the current rated on it ...   surplus current produced by panels will be wasted

thank you

Edited July 6, 20232 yr by VictorD

Up to a point the inverter will regulate the amount of current it draws from the panels. Even if the panel is capable of say 13A, if the inverter's MPPT input is rated at 11A, then it will not take more than that 11A under normal operation. Any potential power generation that the inverter could have delivered with a 13A current will be simply clipped. A waste for sunny days, but on cloudy days you could get more performance using a higher-current panel.

However, there's more to consider, such as the Isc, the short-circuit current under fault conditions. There's an ultimate limit to the current the inverter can handle. Let's say in this scenario it might be Isc of for argument's sake 15A that is the inverter's limit, while the panel could push out 16A, or even more if you place panels in parallel without considering the consequences. I'm just making up numbers here.

Voc is more clear-cut. You don't want to exceed the rated maximum Voc because the inverter cannot easily regulate Voltage. Take care to leave room to cater also for Voltage spikes due to cold temperatures, or the cloud effect.

23 minutes ago, GreenFields said:

Take care to leave room to cater also for Voltage spikes due to cold temperatures, or the cloud effect.

And beware of the minus 6 deg expected on Monday in Gauteng - hehehe

VOC

The open circuit voltage is the maximum voltage that the solar panel can produce with no load on it (i.e. measured with a multimeter across the open ends of the wires attached to the panel ). If two or more panels are wired in series it will be Voc of panel 1 + Voc of panel 2, etc. The voltage is generally highest mid-morning as the sun rises rapidly and the panel temperature is still quite low.
The Voc + approx 3.5 % must be less than the maximum solar voltage permitted by the solar-charge controller. Some controllers shut down if it’s exceeded, while some may continue to operate but the lifespan of the controller could be compromised or it may result in immediate destruction of the charge controller.

ISC

Short-circuit current is the current that flows out of the panel when the positive and negative leads are shorted together. The current can be measured by passing the current through a multimeter configured to measure amps one panel at a time or use a dc clamp meter (this does not harm the panel, but care must be taken to avoid arcing).
The Isc + 20 % is recommended to determine the required current handling capacity of a compatible solar-charge controller. This is the highest current the solar panels will produce under standard test conditions (STC)

I have a Solis S6 6KW, where the inverter states Max PV Isc = 16A and MPPT Range is 90V-520V with a max dc of 600V.
The solar panels TSM-DE19R 575W are rated (STC) Isc = 16.08A and VOC= 45.7V.
I want to install 10x panels, maybe 11 if it will fit my roof. So voltage is good, but the current is a little bit concerning.

Any thoughts please?

2 hours ago, Skusku said:

I have a Solis S6 6KW, where the inverter states Max PV Isc = 16A and MPPT Range is 90V-520V with a max dc of 600V.
The solar panels TSM-DE19R 575W are rated (STC) Isc = 16.08A and VOC= 45.7V.
I want to install 10x panels, maybe 11 if it will fit my roof. So voltage is good, but the current is a little bit concerning.

Any thoughts please?

that 10 should be a perfectly safe install, your voltage is also right in the sweet spot of the mppt, the current is also well within the stated specs.

Edited October 26, 20241 yr by WannabeSolarSparky

16 hours ago, WannabeSolarSparky said:

that 10 should be a perfectly safe install, your voltage is also right in the sweet spot of the mppt, the current is also well within the stated specs.

No, The Short Circuit current of the panels exceed the inverters rating by 0.08A. Can I just ignore the 100mA? What about cloudy and cold days with regards to the current?

7 hours ago, Skusku said:

No, The Short Circuit current of the panels exceed the inverters rating by 0.08A. Can I just ignore the 100mA? What about cloudy and cold days with regards to the current?

should be perfectly safe, the one you need to always worry about is the Voltage as that is the one that will do the most damage if it goes over limits.

Is there any specific reason to use a panel with specs that are basically at the edge of the inverter's limits? Even if it works fine and never fails, there are other options of approx 555W panels that have around 14A Isc (typically approx Voc=49.5V, Vmp=41V, Imp=13.5A). You could put 16 of those 555W panels onto your inverter - 8 panels per MPPT input - and will always be well within the specified parameters, leaving less room for warranty disputes.

14 hours ago, GreenFields said:

Is there any specific reason to use a panel with specs that are basically at the edge of the inverter's limits? Even if it works fine and never fails, there are other options of approx 555W panels that have around 14A Isc (typically approx Voc=49.5V, Vmp=41V, Imp=13.5A). You could put 16 of those 555W panels onto your inverter - 8 panels per MPPT input - and will always be well within the specified parameters, leaving less room for warranty disputes.

Supplier said the 555W and 575W are best priced vs wattage. The 555W passes the Voc and Isc. Its the 575W that is out by 0.08A on the Isc side. Roof can fit 10x panels on the one side, and I'm not sure if I will get more panels in the future. So its 5550W or 5750W for the panels...