MPPT Tracking unstable during load

DIY
, , ,
1

Hey everyone,

I wanted to share my findings regarding an issue I’ve been experiencing with my Victron 100 | 50 MPPT. It seems to be Tracking MPP incorrectly* when external load is turned on, and I wanted to see if anyone else has observed similar behavior or has insights into what might be going on.

Issue Overview

  • The MPPT efficiency is lower than expected, operating at ~94% instead of ~98%. This is observed when the unit is running under 40 °C.
  • It fails to properly track the Maximum Power Point (MPP) after 200W, leading to potential energy loss.
  • I compared it with my Victron 100 | 15 MPPT, and surprisingly, that unit tracks much better under load and reaches an expected efficiency of 98%+.

The setup is as follows:

  1. The MPPT is half a meter away from the Battery Terminal, and the battery is LiFePo4 150Ah 25.6V.
  2. For testing the Victron 100 | 15 MPPT, I have removed the battery wires from the 50Amp controller and connected those wires with an alligator clip.

Link for the videos of testing:
MPPT 100 | 50 - https://youtu.be/fmzIDRIqjBg
MPPT 100 | 15 - https://youtu.be/mfJmof1wRM4

Points to be noted in the video:
The 3 windows you see on the screen are of the Node-Red Dashboard, which shows the Inverter’s output data, MPPT’s data, and Battery’s data.
The other two are of Victron Connect, showing the Trends of the MPPT, and data of Smartshunt.

In the video, you can see that after the SOC reaches 45%, the grid is cut-off and inverter turns on, and from there you can see the changes in the behaviour of the MPPT tracking.

1. Efficiency Calculation

  • I calculated the efficiency using Node-RED on Venus OS, using the formula:

    (SmartShunt Incoming Power + Inverter Load (5.3W)) / Incoming Solar Power

2. Possible Cause: Solar Side Sensor Issue?

  • Since tracking drops after 200W when under load, I suspect an issue with the MPPT’s solar or battery’s voltage or current sensor.
  • If the sensor is misreading values, the MPPT may be selecting the wrong power point, causing it to run inefficiently.
  • This could also explain why the 100 | 15 MPPT tracks properly—it may not have the same faulty sensor behavior.

3. Limitations

  • The 100 | 15 MPPT is limited to 15A, so I couldn’t test under the same high load as the 100 | 50 MPPT. However, from what I’ve noticed, it starts after the charging amps are above 7.5 amps, which is around 200W of solar power.

Request for Insights
Has anyone experienced tracking issues or lower efficiency with their Victron 100 | 50 MPPT?

  • Could a faulty current or voltage sensor explain this behavior?

I appreciate any input or suggestions on further troubleshooting. Let me know what you think! Thanks in advance! :rocket:

2

Alligator clips are not reliable for use in this type of situation - even as a test. They are prone to high and varying resistance, which can compromise results.

3

Hi Mike. Thank you for your response.

So the alligator clip I used was for the 15 Amp controller, and the battery cable that I use for the 50 Amp controller is crimped with pin-type lug, so I decided to use them temporarily for testing.

image
image1280×1280 52.2 KB

However, the 50 Amp controller is directly connected to the battery terminal switch and the Smartshunt.

4

Hi Victron community, I got an update on this issue.

Even after updating to firmware v1.67, which supposedly improves the startup and tracking behavior of the 100|50 model, I’m still experiencing the same persistent issue under load:
The MPPT fails to properly track and maintain the actual maximum power point, especially when the load increases past ~200W.

image
image756×175 4.91 KB

I think there is a calibration issue with the sensors on either the PV side or the Battery side, which causes this bug.

Here’s a video for the tracking bug shown in Victron connect: MPPT 100 | 50 v1.67

Does anyone own a 100 | 50 MPPT so that we can cross-check this issue? I am willing to provide more information on how to recreate this issue.