Victron Smart MPPT Smart 100/50 suddenly dropped voltage/performance

[jessluvs2romp]

I have 720W of solar on the roof of my truck. 3x 180W in series with 2x 100w in parallel.

When I first hooked them up, the MPPT was reading 90V, and supplying a good amount of wattage. Then, the next day it basically stopped working. When I disconnect the solar +/- wires and read the voltage, it is still 90v in direct sun. When I plug them back into the MPPT and switch on the breaker, it for a moment reads 90V then drops down to ~40V or less.

I tried taking out the breaker switch to see if that was the issue, same behavior.

Again - this is all in direct sunlight. The highest it gets now is 120W, and all at the same ambient temperature.

I updated the firmware before the installation.

What am I missing? Did the MPPT just go bad?

 

[ADDvanced]

I also experienced something like this, also with victron recently:

Victron System: Very reliable but then random drop in production?

Hey everyone, been a while. Last winter I installed a 700 watt off grid shed, with victron components (F renogy!!!!), thread with details here: https://diysolarforum.com/threads/please-help-me-victron-system-amperetime-batteries-nothing-makes-any-sense.58710/ Now, ever since I got it...

diysolarforum.com

 

[Rocketman]

two possible issues:

Occasional, (every other year or so), my Victron mppt just needs rebooting. Disconnect the solar, then disconnect the battery- wait for 1 min - reconnect the battery then the solar. Fixed the problem.

Second, are the three 180w panels connected to the two 100w panels into one array?

If so that is part of the problem.

When connecting in series and parallel you:
Series - add the volts - use the lowest amps.
Parallel- add the amps- use the lowest volts.


If you post the specs from both panels- we can help figure out the penalty of connecting them that way.

 

[jessluvs2romp]

the 3x 180w are in series with two 100w's that are in parallel.. its what I needed to do to max the voltage and not go over with the 100/50 mppt.

the issue is it worked great then stopped.. I'll try the rebooting thing tomorrow- thanks for the tip!

 

[Rocketman]

Try another thing - take the two 100w panels out - so you just have the three 180w in series.

You are getting very poor performance- unless your battery is full. You are not getting into absorbing or float stages.



This is what a mppt 100/50 with 700w of power should look like. I think your mixed panel arraignment is causing problems. That’s why I said to try disconnecting the 100w panels.

Good Luck

 

[jessluvs2romp]

why would the 100w's hurt the power output? if I didn't explain it clearly before see the sketch attached.

each 180w's voltage would add to the next in series, and add to the voltage produced by the two 100w's in parallel. yes the two 100w's would be held at the same voltage as each other since they are in parallel, so if one is shaded and the other is not, the voltage of the unshaded 100w would suffer, but their averaged voltage would still add to and increase the total voltage of the entire system. the two 100w panels in parallel could be considered as one 200w panel in series with the others.

i have a background in electrical engineering, but this is my first DIY solar project so please correct me if I'm missing something.

 

[740GLE]

Why did you ever think that was a good wiring set up for those panels? I have never seen that suggested anywhere as a viable option, I don’t even think there’s a term for for this.

I will give it to you it is very creative, I think your going to learn a lot.

My guess is you lost a bypass diode of the 100w panels. Just a guess.

 

[mikefitz]

Comments,
Battery voltage , a low of voltage 7.7 and a high of 13.41 with no absorbtion or float shown, suggest issues with charging.
Possible cause of reducing power , panel interconnection issues, panel failure.
Cold panels may exceed the 100 volt input.

Check all panel connections and perhaps just use the 3 series panels as a test with less complex wiring.

Panel details, battery type and load Information would be useful.

Mike

 

[740GLE]

Comments,
Battery voltage , a low of voltage 7.7 and a high of 13.41 with no absorbtion or float shown, suggest issues with charging.
Possible cause of reducing power , panel interconnection issues, panel failure.
Cold panels may exceed the 100 volt input.

Check all panel connections and perhaps just use the 3 series panels as a test with less complex wiring.

Panel details, battery type and load Information would be useful.

Mike

If the OP applied >100v to the PV input he’d have zero generation and a dead Victron unit.

Remember a poor connection in the PV interconnects will still show good voltage but soon as any current is tried to be pulled you’ll run into a wall.

 

[Rocketman]

The problem is totally the way the panels are wired. You may (or may not) have blow out the diodes.

Post the electrical specs and we can see if there is any way to connect the panels together in a reasonable manner - my guess is there is not.

Probably the best thing is to connect the three panels together in series to your current mppt. Then get another mppt 75/15 (or so) and connect the two 100w panels to that one.

Get the two 100w out of the connections with the 180w panels.

If you really want to understand the why post the all electrical specs of the two sets of panels and I will explain it.

 

[ADDvanced]

yeah man read up on mixing different panels, you are doing it wrong.

 

[HRTKD]

Remember a poor connection in the PV interconnects will still show good voltage but soon as any current is tried to be pulled you’ll run into a wall.

This. It's exactly what I was going to suggest.

As to the panel configuration, I would run the three 180 watt panels in series to the 100/50, then the other panels to a separate controller.