Over-paneling "fix"?

[krell313]

Hi all, I may have a problem with my setup. What I have is an 800 a/hr 24 volt fla battery with a FLEXmax 80 charge controller and 6 370 watt (REC N-peak 2 black series) panels totaling 2220 watts (STC) solar input. I have read about over-paneling and I was wondering if I need to take some precautions.

This installation is in northern California and can possibly see low temps in the mid 20’s but this is rare. The panels are set as 2s3p to keep the voc relatively low, 90 voc at 20 degrees. During the warmer months there is no problem as the cells warm and have a lower output.

My concern is that a cold winter day comes along with an edge-of-cloud effect. I fear that the elevated wattage from the panels may cause harm to the FM80 as I have heard.

I can engineer something that will put a 250 watt load on the panel side of the FM80 if the output current goes above, say 80 amps. The load on the panels would take away some of the available power to the FM80 and reduce the output current faster then the FM80 could current limit. This would be a challenging workaround but I think it would keep the FM80 happy. Do you think it is worth my time to do this with my setup?

 

[zanydroid]

Hi all, I may have a problem with my setup. What I have is an 800 a/hr 24 volt fla battery with a FLEXmax 80 charge controller and 6 370 watt (REC N-peak 2 black series) panels totaling 2220 watts (STC) solar input. I have read about over-paneling and I was wondering if I need to take some precautions.

What is the overpaneling ratio in this setup? Current specs of MPPT (input and output), current of panels. My guess is you have 10A Impp on that type of panel. For 30A into the SCC. This is below a conventional wisdom that the input current should be below max output current.

Also SCCs are damn cheap now, you could also just add a second one that can be programmed to same charge behavior.

 

[krell313]

The Outback FLEXmax 80 is rated at 2000w max solar input for a 24v output at 80 amps. I am running 2220 watts into the FX80 which is 220 watts over max. I have read that this is bad for the SCC. This system is configured as is and can not be modified for another SCC and you are correct about the 30 amps into the FM80.

 

[zanydroid]

The Outback FLEXmax 80 is rated at 2000w max solar input for a 24v output at 80 amps. I am running 2220 watts into the FX80 which is 220 watts over max. I have read that this is bad for the SCC. This system is configured as is and can not be modified for another SCC and you are correct about the 30 amps into the FM80.

Have you reviewed the overpaneling guide on this forum (sorry I don’t have a link).

What sources did you read to see this as an issue, and what exact text?

10% overpaneling is tiny compared to what some forum members do here. +50% and +100% are common

Also a lot of people here stack on other SCC. Sure it might require redoing busbars which is annoying.

 

[krell313]

As I said before, my system is set and not able to add a second SCC. I found the over-paneling guide you mentioned and it does not name my Outback FM80 SCC. I understand if the FM80 fails and I exceeded the 2000 watt max input, I void my warranty. This is why I am asking. I know 10% is not that much but if it blows my SCC, that would be a problem.

 

[zanydroid]

Looks like there isn’t much tribal knowledge about overpaneling this inverter, and the spec sheet is vague.

Adding a panel side load is tricky because solar panels have variable output depending on current draw and voltage. Randomly thinking you can add a DC SSR and switch in a bunch of fat power diodes to drop the voltage. However this is not passively safe wrt the control circuit not noticing the power needs to be burned off.

I think you’re out of luck here with the rules and constraints you’ve set.

 

[krell313]

Looks like there isn’t much tribal knowledge about overpaneling this inverter, and the spec sheet is vague.

Adding a panel side load is tricky because solar panels have variable output depending on current draw and voltage. Randomly thinking you can add a DC SSR and switch in a bunch of fat power diodes to drop the voltage. However this is not passively safe wrt the control circuit not noticing the power needs to be burned off.

I think you’re out of luck here with the rules and constraints you’ve set.

Inverter? Diodes? I was planning of switching in a resistive load across the panels to soak up power when the output power on the SCC was at max. The Outback charge controllers are slow at limiting output power when presented with an edge-of-cloud event and could surge to problematic levels before it corrected itself. My thinking is if you shunt panel power to something other than the SCC, it's output power will drop quickly protecting the device. Remember this may only happen when temps are cold and there is an edge-of-cloud event and this is not a common occurrence.

This post could be a big nothing burger but I was worried if I fried the SCC I would be out $$$.