Expanding PV

Q&A and troubleshooting
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1

Hi,

I’m planning to expand my Victron Installation. I would like to add 10 panels 450 Wp (or something similar - based on what will be available).
The panels will be distributed as follows:

  • 6 panels SW 5°
  • 4 panels SE 31°

Now I have 2 options:

  1. use one MPPT 150/85 for all of them
  2. use MPPT 150/60 for 6 panels SW and 150/35 for 4 panels SE

I believe that since the wiring of 10 panels would be 2s5p, it should be ok to put the strings on different direction (SW - 2s3p + SE 2s2p) on 1 MPPT 150/85. Or perhaps even only 150/70 since all 10 panels wouldn’t be illuminated together at the same time.

However, not sure what solution would be better.

2

As your panels are in different directions you need an MPPT with dual trackers, or in your case 2 MPPTs as the 150 series are single trackers. The MC4 version may have 2 pairs of connectors but the datasheet states it has only 1 tracker in the footnotes.

If you mix panels on different directions on one tracker, the performance of the better string will get dragged down to match the same voltage as the poorer string.

Look at the Victron MPPT calculator

1 Like
3

Hello, thanks a lot for the answer.
I don’t want to be rude, I’m just curious. Are you sure about the need of 2 MPPTs with dual trackers? Currently I have one MPPT 150/100 with 12 panels:

  • 2 heading SE (2s1p)
  • 10 heading SW (2s5p)

…and it works ok. At the morning, when the sun rises, the 2 panels makes about 700 W and after lunch, the 10 panels creates about 4700 W (max of course), so I believe it should work. Since the panels are not in series (always only 2 panels in series), they shouldn’t affect each other should they?

So that’s the reason why I was thinking about using only one MPPT 150/80 with 4 panels (2s2p) to SE and 6 panels (2s3p) to SW.

But since I’m gonna change the whole installation, I will use 2 separate MPPTs as you advised:

  • the current 12 panels will all be heading all to SW on MPPT 150/100
  • 6 new panels heading to SW - MPPT 150/60 (perhaps 150/45, not sure yet)
  • 4 new panels heading to SE - MPPT 150/35 or 150/45, also not sure yet.

To be clear, I didn’t install the current system, it was made by company.

Again, thanks a lot for your reply!

4

You need 1 MPPT with dual tracker or 2 MPPTs.

On your current set up you have 2 panels in one direction and 10 panels in another. At dawn the 2 panels will provide some power and the 10 panels very little so the maximum power point tracks the 2 panels. Once the main 10 panels start to power up, the maximum power point will always be with the 10 panels and the voltage from the 10 panels will be to high for the 2 panels and they will produce very little. This works OK because it is a small set in one direction and a large one in another.

Now you are talking 4 panels in one direction and 6 in another so they ate closer matched and the lost production will be greater. Yes it will work but your power output with 1 tracker will always be lower than if you had 2 trackers. With 2 trackers you always have the maximum possible from both directions. With a single tracker at least one direction will be producing less than it could, possible both directions. It depends how much you want to compromise between power production and install cost.

2 Likes
5

OK, great, thanks a lot for the explanation! :slight_smile: I really appreciate that