Schneider Context MPPT 100 - Trouble

[knexbuilder]

So I just installed a couple of Schneider Inverters and matching MPPTs. Well actually only one MPPT is hooked up at the moment. I needed one more breaker to install the second one. Anyway, put the system into service late Saturday afternoon (5/8/23) and was more than impressed. It handled everything I threw at it and asked for more. I was generating power from my panels; life was good. Did more testing Sunday, again all is well.

Today I get back home from work and check on the system and notice that the battery voltage is low (53V) and should be getting charged from the solar panels. The MPPT controller was indicating it was connected to the battery, but that no charging was taking place. I went into the settings and investigated, and forced the controller into a float state just to see if anything happened. Nothing.

I got my volt meter and discovered something curious. I have no voltage at my MPPT positive and negative terminals. If I disconnect the wires and measure the voltage from wire to wire I get around 340V. Once I re-land the wires I read zero again. I removed the wires and did a continuity check from the negative to positive PV terminals and I get a beep indicating a low resistance path between the two. Any clue what is going on???

Just so folks are aware I had two strings of eight 445watt panels connected to the MPPT for a grand total of 7120 theoretical watts connected to the controller. Based on numbers I was seeing Saturday and Sunday during full sun I was getting around 4-5kW of output from the panels. Overpanneling shouldn't be an issue for MPPTs based on my reading on the forum correct? Looking at the graphs from schneider today it seems to have stopped producing around lunch for whatever reason.

Did I fry the unit some how? Do I have a lemon?

 

[knexbuilder]

See attached for clearer description of what I am talking about.

 

[ElectricIslander]

Yikes - Having your charge controller present a dead shorted input after only a few hours in operation doesn't sound good. Can you check your other unused charge controller with an ohm-meter to see what it's input resistance is?

Sounds like time to alert Schneider asap that your unit had an early failure if the input resistance of the un-used unit isn't the same as your unit causing problems.

 

[Shimmy]

What time did you get home for those readings?

34% Over-panelling seems a little high to me. My read of the battery graph is that it hit 60A the first time, throttled back/cooled off the MPPT, then hit it again and shut down. I wonder if it was a thermal overload.

 

[knexbuilder]

Yikes - Having your charge controller present a dead shorted input after only a few hours in operation doesn't sound good. Can you check your other unused charge controller with an ohm-meter to see what it's input resistance is?

Sounds like time to alert Schneider asap that your unit had an early failure if the input resistance of the un-used unit isn't the same as your unit causing problems.

I should have mentioned that I did check the other controller for comparison and no short circuit or resistance measurement at all. Both the Pv - and the Pv + are separate with no connection between.

In answer to @Shimmy , I took the readings at 4pm (ish) yesterday and had good sunlight. The arrays that I had connected to this controller face west so ideal panel output is not the norm. Looking at the battery current shows 60amps to the battery like you said. This should have been at or around 56Vdc, so that would equate to 3360 watts going to the battery. These units are supposed to be able to charge at a max of 6000 watts, so I don't think I stressed the unit based off the graph. Listening to Schneider's video for the smaller unit (MPPT 80 600) the lady seems to indicate that it is very accepting of overpanneling

(time stamp 4:50 - 7:15 minute marks). Her comment was 25% over sizing is normal, and that she had seen larger in norther areas to compensate for lack of ideal panel/lighting.

 

[pvdude]

Don't know if this helps, but I have three of the Schneider 100A 600vdc CC in service here.
Very similar PV voltage and amps to yours. No issues so far.
However, some of my PV is South facing, some East, some West.
Works well to flatten and extend the power generation through the day.
At around 2PM, on a good solar day, the PV output peaks at 11-13kw.
I am waiting to see what this Summer's power pattern looks like, (clouds) before adding more PV.

 

[knexbuilder]

A beautiful setup! Thank you for sharing, that does make me thing that I am not doing something stupid with my setup.
I will be duplicating that because I have east and west facing arrays on my shed (2 east, 2 west).

 

[knexbuilder]

I found this gem on the schneider website (link below). The "7kW or more" re-assures me that I did not fry it from over paneling.

https://solar.se.com/us/en/product/conext-mppt-100-600-6kw-solar-pv-charge-controller/

 

[400bird]

That sounds like high resistance somewhere in the PV circuit. Voltage reads normal with no load, but as soon as you apply a load the voltage drops.
Do you have a breaker and or combiner box? I'd check the voltage there too.
But, the high resistance could be anywhere in the circuit.

I realize you measured low resistance inside the MPPT, but there are capacitor in there and I'm not sure you can get a reliable resistance measurement inside the MPPT.

If the MPPT was dead shorted internally, wouldn't it be creating nearly 4-5kw of heat (your PV array output) ?

 

[knexbuilder]

That sounds like high resistance somewhere in the PV circuit. Voltage reads normal with no load, but as soon as you apply a load the voltage drops.
Do you have a breaker and or combiner box? I'd check the voltage there too.
But, the high resistance could be anywhere in the circuit.

I realize you measured low resistance inside the MPPT, but there are capacitor in there and I'm not sure you can get a reliable resistance measurement inside the MPPT.

If the MPPT was dead shorted internally, wouldn't it be creating nearly 4-5kw of heat (your PV array output) ?

Hmm maybe. Attached is exactly how the system is configured. No combiner box. With nothing connected to the mppt there is a short between pv- and PV+. I do not measure any path for electricity in my other mppt.

 

[Shimmy]

Can you disconnect the SPD to test?

 

[400bird]

I do not measure any path for electricity in my other mppt.

Well if they two MPPT 100/600 measure differently, you may have nailed it right there.

Any faults or alerts for the unit on Insight?

 

[knexbuilder]

@Shimmy yes, I disconnected the SPD entirely. No difference.

@400bird strangely not even a beep! No codes, no errors or warnings. Just nothing. I have an e-mail into signature solar, no response yet. I suspect they are snowed under.

 

[400bird]

Have you tried this array connected to your second MPPT? Or tried measuring the current with an amp meter? If the input was shorted, you'd see full array ISC on the PV wiring.

I'd contact Schneider, they aren't the quickest to respond, but it feels like you will get a better response from the manufacturer.

 

[SpongeboB Sinewave]

BOTH MPPTs are showing this shorted input behavior ?

If only 1 was doing that, I would say that maybe the unit is broken. Input shorted. Possibly both but....

Do you have a DC clamp meter ? If you do then you could check to see if the PV positive and negative have short-circuit current while connected which might confirm a shorted input to the charge controller.

Has this system worked before ? If not, then maybe the positive and negative PV lines are reversed ?

boB

 

[knexbuilder]

@SpongeboB Sinewave Thankfully only the one MPPT is exhibiting such behavior. The second unit is working like a charm. I tried a clamp meter on it and the current it read we ridiculously low. 0.19amps. I tried it a couple times. Same result. Unsure what exactly is happening to the unit. Signature Solar called me today and asked for some additional details. Working on providing them the info requested.

@400bird I hooked both arrays, that were originally connected to the failed controller, to the functioning controller. No issues. Measured 330VDC at the controller Pv terminals and the controller started harvesting sunlight. I tried both arrays independently. I had to extend the wires in a "none code" way to reach the second controller :D It would appear that my arrays are not the issue thankfully. Something has gone bonkers inside the controller it would seem.

 

[Shimmy]

Do you have RSD on the panels?

 

[knexbuilder]

Yes I do. They are functioning correctly.

 

[400bird]

@SpongeboB Sinewave Thankfully only the one MPPT is exhibiting such behavior. The second unit is working like a charm. I tried a clamp meter on it and the current it read we ridiculously low. 0.19amps. I tried it a couple times. Same result.

What were you measuring? How were you using the clamp meter? Do you know you need to grab just one conductor? Not both positive and negative together in the meter jaws.

Unsure what exactly is happening to the unit. Signature Solar called me today and asked for some additional details. Working on providing them the info requested.

@400bird I hooked both arrays, that were originally connected to the failed controller, to the functioning controller. No issues. Measured 330VDC at the controller Pv terminals and the controller started harvesting sunlight. I tried both arrays independently. I had to extend the wires in a "none code" way to reach the second controller :D It would appear that my arrays are not the issue thankfully. Something has gone bonkers inside the controller it would seem.

Well, that's good news I suppose. I suppose they are allowed to have a component fail at 10 hours every once and a while.

 

[knexbuilder]

What were you measuring? How were you using the clamp meter? Do you know you need to grab just one conductor? Not both positive and negative together in the meter jaws.

Well, that's good news I suppose. I suppose they are allowed to have a component fail at 10 hours every once and a while.

Haha the simple questions are always best to ask. Yes I am aware how to use an amp meter which is why the reading surprised me.