Cooked charge side of Growatt.

UH OH!
Looks like I may have cooked the charge side of my controller/inverter. The inverter works but not the solar controller. I have 12 x 250W 38VOC 8.3A panels on the roof. I have had the system working fine with just one series string of 4. Yesdy I tried to connect up all three strings of 4 so 3P4S. This equals 136V tested, 25A. Specs for the controller is 145V VDC. Would that be VOC? Anyway thats what the manual states, VDC. Well within it’s amperage specs. Now I have a circuit breaker of 32A between the panels and the controller. Um, yep the breaker is an AC unit. When I connected the 50A anderson plug, I got a crack at one of the panels and the charge side of the controller went out. I flicked the breaker but it continued to arc across the terminals inside the breaker obviously. Checked with one panel but no go. Obviously the controller is damaged. The thing that I don’t understand is you cannot connect panels up wrong with there being male/female connector. ImI’m using the wire type three way joiners to connect the strings.
Can anyone see where a potential issue may lie as I’m stumped.
The controller is a Growatt SPF5000TL.
Onya’s

38 VOC X 4S is 152 VOC. Manual says Max Open Circuit Voltage (VOC) 145?
“three strings of of 4 so 3p4s” This means you connected groups of 3 in parallel then after all panels were in groups you series connected all of them. So you connected 3 750 watt panels in series to the controller. Each 750 panel having 8.2 amps and VOC of 152. I don’t suppose you put fuses in the parallel circuits that would mean you would have had to fuse every panel?
What about a crack?

acdoctor said:

38 VOC X 4S is 152 VOC. Manual says Max Open Circuit Voltage (VOC) 145?
“three strings of of 4 so 3p4s” This means you connected groups of 3 in parallel then after all panels were in groups you series connected all of them. So you connected 4 750 watt panels in series to the controller. Each 750 panel having 25 amps and VOC of 38. I don’t suppose you put fuses in the parallel circuits that would mean you would have had to fuse every panel?
What about a crack?

Click to expand...

Oof that’ll do it

acdoctor said:

38 VOC X 4S is 152 VOC. Manual says Max Open Circuit Voltage (VOC) 145?
“three strings of of 4 so 3p4s” This means you connected groups of 3 in parallel then after all panels were in groups you series connected all of them. So you connected 4 750 watt panels in series to the controller. Each 750 panel having 25 amps and VOC of 38. I don’t suppose you put fuses in the parallel circuits that would mean you would have had to fuse every panel?
What about a crack?

Click to expand...

No, 4 in series which read when tested 136V.
Amps in series would be 8.2A
Volts in parallel would be 136V ( all strings measured under the max VOC).
Amps in parallel would be 24.6A.

AlanH said:

No, 4 in series which read when tested 136V.

Click to expand...

38VOC x 4 =152VOC which is over the VOC rating of the Growatt.

136V Vmp has nothing to do with it. Vmp is loaded voltage, VOC is Voltage Open Circuit. Big difference there.

AlanH said:

Amps in series would be 8.2A
Volts in parallel would be 136V ( all strings measured under the max VOC).

Click to expand...

No, VOC is the open circuit voltage without a load. You exceeded the 145V VOC limit of the Growatt. The correct operating range of your unit according to the specs you show is 60 to 115V which is Vmp. You measured 136V under load which is higher than the operating range.

AlanH said:

Amps in parallel would be 24.6A.

Click to expand...

I looked for an input spec on PV but none is listed. Max PV watts appears to be 4500W. You are under max watts. I can't say on amps.

Zwy said:

38VOC x 4 =152VOC which is over the VOC rating of the Growatt.

136V Vmp has nothing to do with it. Vmp is loaded voltage, VOC is Voltage Open Circuit. Big difference there.




No, VOC is the open circuit voltage without a load. You exceeded the 145V VOC limit of the Growatt. The correct operating range of your unit according to the specs you show is 60 to 115V which is Vmp. You measured 136V under load which is higher than the operating range.


I looked for an input spec on PV but none is listed. Max PV watts appears to be 4500W. You are under max watts. I can't say on amps.

Click to expand...

The panels are rated at 38VOC under controlled lab conditions. This does NOT mean that that’s what’s going through to the controller. What is actually measured is what is going through to the controller, which is an average of 136V. It doesnt matter what is written on the panel, its whats being sent to the controller that does.

60-115VDC is the PV MPPT voltage range. 145VDC is the max PV is the max VOC.

Im well under with the amps

AlanH said:

Can anyone see where a potential issue may lie as I’m stumped.
The controller is a Growatt SPF5000TL.
Onya’s

Click to expand...

We have been trying to explain the issue. If it hasn’t got you already it will as soon as the weather cools any.

I also suspect you have a portion of the panels miss-wired in a short with the rest.

I have the 3k growatt with 145 VOC. I have 5s4p 22x5=110 VOC. Vamp is 80. 5 amps x4 strings is 20 amps.

I

acdoctor said:

We have been trying to explain the issue. If it hasn’t got you already it will as soon as the weather cools any.

I also suspect you have a portion of the panels miss-wired in a short with the rest.

Click to expand...

I know you have been trying to explain the issue, so I ask the question which people seem to not want to answer. I’ll try again.

The VOC rating on the panel is 38V. Now I have been advised that the rating on the panel doesn’t particularly reached hence why I measured it which is 136VOC. Wouldnt what is measured be the value to go by?

I appreciate what has been advised but to understand what has been stated, questions are asked. What has the weather cooling come in to it? Panels miss wired? I’ll check put I can’t see how it can be done with male and female connectors.

Thanks for your time, I do appreciate it.

AlanH said:

I

I know you have been trying to explain the issue, so I ask the question which people seem to not want to answer. I’ll try again.

The VOC rating on the panel is 38V. Now I have been advised that the rating on the panel doesn’t particularly reached hence why I measured it which is 136VOC.

Click to expand...

Open circuit or loaded circuit? VOC is open circuit, that is without anything connected to the series. You measure the voltage at the ends of the series string.

Loaded circuit is when you have anything that could be a load connected to the series string. A SCC is a load.

The reason for looking at VOC is when a battery gets fully charged, the SCC will reduce the load placed on the series string or completely stop any load on the series string. The voltage of the string will rise as a result.

The components of the SCC are voltage rated, thus the hard limit by the manufacturer. Exceeding the limit will result in failure of components. Damage can result from arcing, similar to the breaker you saw that continued to arc internally. Or the magic smoke is released in capacitors and other electrical circuits in the SCC.

AlanH said:

Wouldnt what is measured be the value to go by?

Click to expand...

No, you have to go by the max open circuit voltage which is VOC. Again, as the SCC reduces or completely stops any load on the series string, the series string voltage will rise.

AlanH said:

I appreciate what has been advised but to understand what has been stated, questions are asked. What has the weather cooling come in to it?

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When panels are colder, the voltage goes up. When panels are warmer, the voltage goes down.

Here is a calculator for computing string VOC in colder weather. https://www.midnitesolar.com/sizingTool/

AlanH said:

Panels miss wired? I’ll check put I can’t see how it can be done with male and female connectors.

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Did you check polarity of each panel when you installed them? I consider it essential as the ?'s at the factory may not have incorrectly installed the ends/stickers for polarity.

However, even if you did have one panel with incorrect polarity, it would reduce that series string voltage. It can also blow the diodes in the panel with reversed polarity if the voltage of the string is high enough.

AlanH said:

Thanks for your time, I do appreciate it.

Click to expand...

No, panels WILL reach and exceed the printed VOC.
Just because you didn’t measure it doesn’t mean that it didn’t happen.

Yes

AlanH said:

This equals 136V tested, 25A. Specs for the controller is 145V VDC. Would that be VOC?

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The manual and the solar panels are both very clear in their terminology.

Solar panel VOC = 36
Inverter maximum VOC = 145

Neither of them mention "measured" as a term for their limits, so you are comparing apples and oranges. Your measured value has no bearing on the VOC limits.

This inverter will only handle 3 of your panels in series. I'm sorry you've lost the solar charge controller in your inverter, and it won't be covered under warranty, however you can buy solar charge controllers separately if you don't want to replace or repair the inverter. Consider buying cheap $100 charge controllers if you plan to experiment and push the boundaries in the near future.

This is the one I'm playing with:


And as a side benefit, you won't have to re-wire your array as its maximum VOC is 160vdc, so you can keep you panels in 4s as still not exceed the charge controller's rating. It's running pretty close tot he limit, though, with only a few volts margin - since it's a cheap controller I'd risk it, but I don't recommend people run any of their equipment close to their limits on a regular basis.

Design in a margin and you'll avoid so many issues.

Also, be aware that you risk your batteries when the solar charge controller fails, so if you have a lot invested in storage you should make sure they are protected with an automatic cutoff for overvoltage conditions if, again, you want to run any of your equipment close to their limits with no margin for error.

stienman said:

Yes


The manual and the solar panels are both very clear in their terminology.

Solar panel VOC = 36
Inverter maximum VOC = 145

Neither of them mention "measured" as a term for their limits, so you are comparing apples and oranges. Your measured value has no bearing on the VOC limits.

This inverter will only handle 3 of your panels in series. I'm sorry you've lost the solar charge controller in your inverter, and it won't be covered under warranty, however you can buy solar charge controllers separately if you don't want to replace or repair the inverter. Consider buying cheap $100 charge controllers if you plan to experiment and push the boundaries in the near future.

This is the one I'm playing with:

https://www.amazon.com/PowMr-Controller-Backlight-Battery%E3%80%90Software-Version%E3%80%91/dp/B0719PGGBS/

And as a side benefit, you won't have to re-wire your array as its maximum VOC is 160vdc, so you can keep you panels in 4s as still not exceed the charge controller's rating. It's running pretty close tot he limit, though, with only a few volts margin - since it's a cheap controller I'd risk it, but I don't recommend people run any of their equipment close to their limits on a regular basis.

Design in a margin and you'll avoid so many issues.

Click to expand...

“
Solar panel VOC = 36
Inverter maximum VOC = 145

Neither of them mention "measured" as a term for their limits, so you are comparing apples and oranges. Your measured value has no bearing on the VOC limits”

Thanks Stieman, VOC is 38 but yeah. Where I have been getting confused is I couldnt see what the VOC had to do with anything when what’s measured would. Now, my panels are second hand. I measured every panel before they went on the roof. I was getting 36-37 VOC but there was a very hint of overcast. Here in Australia we have only just gone from winter into spring so we are still getting frosts and cool days.

Yep, bit of a biartch the solar charger side is cooked. One of Growatt’s basic controllers will pair with this unit so it then gives me back the charger and inverter as per the original. Very reasonably priced.

acdoctor said:

No, panels WILL reach and exceed the printed VOC.
Just because you didn’t measure it doesn’t mean that it didn’t happen.

Click to expand...

Doc, I do have a little difficulty understanding what you write sometimes. I measured the VOC and IMP of each panel prior to lifting onto the roof. I then measured the VDC of each string averaging 136V.

Cheers.

Zwy said:

Open circuit or loaded circuit? VOC is open circuit, that is without anything connected to the series. You measure the voltage at the ends of the series string.

Loaded circuit is when you have anything that could be a load connected to the series string. A SCC is a load.

The reason for looking at VOC is when a battery gets fully charged, the SCC will reduce the load placed on the series string or completely stop any load on the series string. The voltage of the string will rise as a result.

The components of the SCC are voltage rated, thus the hard limit by the manufacturer. Exceeding the limit will result in failure of components. Damage can result from arcing, similar to the breaker you saw that continued to arc internally. Or the magic smoke is released in capacitors and other electrical circuits in the SCC.



No, you have to go by the max open circuit voltage which is VOC. Again, as the SCC reduces or completely stops any load on the series string, the series string voltage will rise.



When panels are colder, the voltage goes up. When panels are warmer, the voltage goes down.

Here is a calculator for computing string VOC in colder weather. https://www.midnitesolar.com/sizingTool/



Did you check polarity of each panel when you installed them? I consider it essential as the ?'s at the factory may not have incorrectly installed the ends/stickers for polarity.

However, even if you did have one panel with incorrect polarity, it would reduce that series string voltage. It can also blow the diodes in the panel with reversed polarity if the voltage of the string is high enough.

Click to expand...

Yep, I understand the drop in volts and amps as the state of charge maximises.

I measured the VOC of the string.

Sorry guys for being a little slow on the uptake. I struggle with electrical but I will have a go. Anything mechanical I have no issue with even with one eye tied behind my back.

Thanks for your help guys.

Al.

Hi Guys,

So ive read the voltage off each string of 4. One is 131.3V and the other is 133.1V. Now if I parallel these I get 3.197V before the controller. Doesnt make sense to me!

I would think in order to readings like that you would have to connect the positive of one string to the negative of the other. If the both strings were electricly identical they would cancel each other out and you would measure 0 volts.
I think you should check the polarity at each panel and mark the positive wires with some tape. As you assemble continue to use the tape to ensure you are keeping positive and negative where you need them to be. A drawing would help but only when drawing is completely employed.

acdoctor said:

I would think in order to readings like that you would have to connect the positive of one string to the negative of the other. If the both strings were electricly identical they would cancel each other out and you would measure 0 volts.
I think you should check the polarity at each panel and mark the positive wires with some tape. As you assemble continue to use the tape to ensure you are keeping positive and negative where you need them to be. A drawing would help but only when drawing is completely employed.

Click to expand...

Thanks Doc. As it turns one of the string leads had the MC4’s reversed.

Thankyou.