MPPT Derating / Throttling - Can PV voltage affect heat generated?

Question

question

neoneddy asked Jul 29, '20

MPPT Derating / Throttling - Can PV voltage affect heat generated?

I'm trying to solve my MPPT Derating issue, I have 2600 watts of panels connected to 2x 100|50 Blue Solar Charge Controllers. The panels are in 2 groups of 4 in series parallel pairs with a voltage of around 80 volts. My battery bank is 24 volts.

I have a fan on the charge controllers, bad news is they are stacked, so the hot air form one tries to cool the next, but they both throttle. I also have ventilation of the charging / inverter / battery bay, but it still throttles. I see they derate at 40c, so I hit that often.

I'm wondering if there is any advantage to going to all parallel on my panels? Is excess heat being generated by stepping down 80v to 24v vs 40v to 24v ?

MPPT Controllers temperature

1

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

joeoffgrid commented · Jul 02, 2021 at 06:48 AM

I may have a similar issue with my setup. Is there any way to surely know the controllers are derating? I don't have as much solar power as you do.

I'm suspecting the derating especially on the LOAD terminals.

0 ·

Modifications Space

Node Red Space

Answer 1 · 2020-07-29T18:54:30Z

Alexandra answered · Jul 29, 2020 at 06:54 PM

@neoneddy

There is not really an advantage to changing the configuration of the panles as watts are watts.

Each charge controller will be processing 1200w of power (50A x 24V). So that's the heat it has to deal with. Regardless of how you configure the panles it will work to charging at the 50A unless you set the output a bit lower in software.

You can try space your mppts away from the surface they are mounted on for better air flow or attach it to the vehicle skin (some even use heat sink paste for better coupling) so that the heat is taken away by the body of the vehicle as well. Or mount them on aluminum rails. But definitely if you are able get some more space between them.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 2 · 2021-07-01T17:36:17Z

thumpstead answered · Jul 01, 2021 at 05:36 PM

@neoneddy

Most MPPT charge controllers that I have seen (that have published curves) have a higher conversion efficiency with PV operating voltages closer to the charge voltage. I believe this corresponds to typical DC-DC buck converter topologies. The efficiency differences are highest at low current levels where there may not be as much heat generated. At higher current levels the efficiency does not differ by as much. However, if you have 2400w of power being processed in an enclosure and the efficiency difference is only 2%, that is still ~50W of additional heat that needs to be dealt with.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

question