Info on Solar panels

[Merl Priester]

I bought bougerv 100 watt 9BB panels. 800 watts, 4s2p
I am trying to figure the max voc but cannot find the info to use. It only show +-3% but does not tell if that is max in cold weather.


These are on my trailer but want to put a grid tie when it is parked.

Thanks for your help.

 

[sunshine_eggo]

I bought bougerv 100 watt 9BB panels. 800 watts, 4s2p
I am trying to figure the max voc but cannot find the info to use. It only show +-3% but does not tell if that is max in cold weather.

No panel gives you that information. The values given are for 25°C/77°F. most reputable manufacturers provide a datasheet with the Voc temperature coefficient. Unfortunately, that's not the case here:

https://cdn.shopify.com/s/files/1/2672/9544/files/200W_12V_9BB_Mono_Solar_Panel.pdf

For unknown values, I use -0.4%/°C. MOST panels tend to be more favorable than this value. Here's the calculation:

21.4V * 4S = 85.6V

Since you haven't given any information, I'm going to assume your controller has a 100V limit.

100V - 85.6V = 14.4V - difference between nominal and maximum.

14.4V/85.6V = 16.8% - i.e., a 16.8% increase in voltage will hit the MPPT Voc limit.

16.8% / -0.4%/°C = -42°C

since the panels are defined at 25°C, you add 25°C and -42°C yielding -17°C

These are on my trailer but want to put a grid tie when it is parked.

That sounds like a shit show. Have you actually looked into the feasibility of this?

 

[Merl Priester]

No panel gives you that information. The values given are for 25°C/77°F. most reputable manufacturers provide a datasheet with the Voc temperature coefficient. Unfortunately, that's not the case here:

https://cdn.shopify.com/s/files/1/2672/9544/files/200W_12V_9BB_Mono_Solar_Panel.pdf

For unknown values, I use -0.4%/°C. MOST panels tend to be more favorable than this value. Here's the calculation:

21.4V * 4S = 85.6V

Since you haven't given any information, I'm going to assume your controller has a 100V limit.

100V - 85.6V = 14.4V - difference between nominal and maximum.

14.4V/85.6V = 16.8% - i.e., a 16.8% increase in voltage will hit the MPPT Voc limit.

16.8% / -0.4%/°C = -42°C

since the panels are defined at 25°C, you add 25°C and -42°C yielding -17°C




That sounds like a shit show. Have you actually looked into the feasibility of this?

The solar to battery controller is a Victron 150/60. I knew it was OK.. But I want to grid tie these when not using the trailer. Most of the inverters are 90v max. Thank you for the information. I know the 90v is getting close. But I figured the mppt will lower the voltage after initialization. The victron does lower the voltage.

 

[Supervstech]

The solar to battery controller is a Victron 150/60. I knew it was OK.. But I want to grid tie these when not using the trailer. Most of the inverters are 90v max. Thank you for the information. I know the 90v is getting close. But I figured the mppt will lower the voltage after initialization. The victron does lower the voltage.

It doesn't matter that the voltage will lower under load,what matters is IF THE PANEL EVER DROPS BELOW 20C AMBIENT, A 90V MAX INVERTER WILL GO POOF ..

 

[Supervstech]

This shows that with a coefficient of 3% you have to stay above 10C ambient to keep a 90V max inverter alive

 

[Merl Priester]

Well the inverters woul have to have a much higher voltage limit.. It doesn't look like there are any that will do this.
The voltages are to low for most string inverters and too high for individual inverters like an enphase.

I guess at this point I just won't attempt it. Thanks for the input.