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Louw Jansen van Rensburg avatar image
Louw Jansen van Rensburg asked

MPPT 150/70 output stuck at 470 watt after connecting more panels?

Hi V Community.

I stay in South Africa.

Being in the Southern Hemisphere our panels gave North for optimal performance.

I have 3 parallel string of 3 x 330 watt Canadian Solar panels connected in series. The panels was mounted to all face South. Incorrectly.

I moved my panels to face North

I could only move 1 string at a time due to time constraints.

Moving the first string resulted in 1 string (3 panels) facing north and 6 facing south. With this configuration the output of the MPPT increased from a peak of 800+ Watt to 1250+ Watt!

I was very excited to move the next string to have a total of 6 panels facing North and only 3 facing South.

When the second string was moved the MPPT output dropped to less than 500 Watt.

The interesting part is that the output curve rise quickly to its max of approx 470 Watt and remains at that output until late the afternoon when it quickly drops of to zero. It seems like some limit is reached which prohibits the PV yield to increase further.

Everything was looking promising until I disconnected the strings and reconnected them to the combiner box after the repositioning of the 2nd string.

I can confirm:

All strings Voc = 123V

Combiner Voc = 123V


What is my next steps in troubleshooting?

Can the MPPT be reset to default settings?


Thank you in advance.


Louw

MPPT Controllers
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2 Answers
JohnC avatar image
JohnC answered ·

Hi Louw. From a previous post, you have an EasySolar box and some sort of 'exotic' batts. And that's fine, so is your decision to face your panels north. Your Voc is as expected. Troubleshooting ideas:

1. With a combiner box, you wouldn't be the first to inadvertently mix polarity from strings there, and if so one string will largely cancel the other. Make sure, even to the point of pulling the cables and testing with a multimeter. Take care, that's a lot of V you're dealing with.. backed with A.

2. Your batts are possibly close to being fully charged, and can't accept full current. That may be the 'limit' you seek, and is actually what every offgridder wants to see - daily, and usually the longer time the system spends there in Abs/Float the better. It may be working well, but try putting a load on the batts to see if charge W responds. It should rise to compensate for what you're taking out.

3. Watch your charge V as a priority. Panel Voc is fine to view from a technical aspect, But it is 'open circuit', and W will influence it. If your panels are at full production that will drop to Vmp, and should get closer to that rating of the panels.

4. Your batt bms *may* get involved, depending on what it is, but if the Vbat under charge is what it's designed for, then all is likely working fine.

5. VRM portal access is great if you can/have that set up, and will help with understanding what's happening.

6. You may need extra kit to change mppt settings (until maybe firmware updates bestow that capability upon us), but determine a need before going there.

Maybe these things can help, but come back as you need. Good luck..

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Louw Jansen van Rensburg avatar image
Louw Jansen van Rensburg answered ·

Hi John C.


Thank you for your help. I finally realised that I limited the MPPT charge current to 10A. This impacted the EasySolar system performance.

Thank you again John


Louw

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