Growatt 3600 - String voltages - MPPT1&2

[73henny]

Hi all,

Would anyone who has a Growatt inverter have a look at their voltage trends for MPPT 1&2 please?
My system was installed on Monday and I've noticed a different trend for each string as shown below. The string with the maxed out 150v is producing less power than the other string. The strings seem to test out okay.

Any help appreciated.

Thanks,

 

[Barx]

Are the 2 strings on different orientations?
With PV panels, the voltage is affected by heat. Could it be that one set in direct sun, so is hotter? therefore voltage could fluctuate a bit.
Also, how many panels are on each string? Doesn't a lot of Volts for a string connected to a 3600 inverter.
Most trackers don't even spring into life until 80 - 100v is applied.

 

[73henny]

Are the 2 strings on different orientations?
With PV panels, the voltage is affected by heat. Could it be that one set in direct sun, so is hotter? therefore voltage could fluctuate a bit.
Also, how many panels are on each string? Doesn't a lot of Volts for a string connected to a 3600 inverter.
Most trackers don't even spring into life until 80 - 100v is applied.

The strings are side by side so seeing exactly the same conditions and each string has 6 panels.
You can see the voltages are exactly the same for a while and then move away from each other.
In the trend below the outputs from each string follow each other but one is at times quite a bit higher than the other.

 

[stuboy]

looks like a shading issue. Even a wire across one set of panels will cause a significant loss, check shading and get back to us ;-)
Or one set is getting hotter than the other?
Cheers
Stuart

 

[Si_Oakwood]

These were our voltages yesterday, was cloudy so not much generation but our voltages are fairly consistent every day. Higher V than OPs though (no idea why that is), 260-280V. MPPT1 is east facing, MPPT2 is west facing.

 

[up_north]

These were our voltages yesterday, was cloudy so not much generation but our voltages are fairly consistent every day. Higher V than OPs though (no idea why that is), 260-280V. MPPT1 is east facing, MPPT2 is west facing.View attachment 13953

That’s an interesting graph. What would have caused that drop back from 140 to 100 before shooting all the way up at the beginning of the day?

 

[Si_Oakwood]

That’s an interesting graph. What would have caused that drop back from 140 to 100 before shooting all the way up at the beginning of the day?

not sure, it does it most days, possibly just some cloud causing it to drop below the 100V min required or maybe it's the self testing. Looking at the solar power at the time it happens it's around 5W so it isn't really generating much when it happens.

 

[up_north]

not sure, it does it most days, possibly just some cloud causing it to drop below the 100V min required or maybe it's the self testing. Looking at the solar power at the time it happens it's around 5W so it isn't really generating much when it happens.

Ok thanks. To a lesser extent it looks as if it does something similar just before it shuts down, goes down, jumps up a tad before finally shutting down.

This is a slight concern I have with the Givenegry inverter I have on order. It has quite a high 150v startup requirement and each MPPT has a range of 150v-550v Four of my ten panels will be in full shade until about 9.30am, so don’t know whether to put those four on one MPPT and the other six on another. Not sure if we’re supposed to look at the solar panel’s voltage at maximum power or the open circuit voltage. But if it’s the former then four panels will be just over 150v. We’re getting Tigos anyway due to late afternoon shadow from the chimney so I’m wondering if putting all ten on a single MPPT would be better.

 

[Si_Oakwood]

Ok thanks. To a lesser extent it looks as if it does something similar just before it shuts down, goes down, jumps up a tad before finally shutting down.

This is a slight concern I have with the Givenegry inverter I have on order. It has quite a high 150v startup requirement and each MPPT has a range of 150v-550v Four of my ten panels will be in full shade until about 9.30am, so don’t know whether to put those four on one MPPT and the other six on another. Not sure if we’re supposed to look at the solar panel’s voltage at maximum power or the open circuit voltage. But if it’s the former then four panels will be just over 150v. We’re getting Tigos anyway due to late afternoon shadow from the chimney so I’m wondering if putting all ten on a single MPPT would be better.

I'm no expert but if they're all on one string then 1 faulty panel/wire or a bit of snow could significantly reduce your output until it's sorted, IMO surely better to use both MPPTs?

 

[73henny]

looks like a shading issue. Even a wire across one set of panels will cause a significant loss, check shading and get back to us ;-)
Or one set is getting hotter than the other?
Cheers
Stuart

Thanks for you reply. Theres no shading - both strings are identical in size and shape and are side by side. Similarly one string won't be any different in temperature to the other.

These were our voltages yesterday, was cloudy so not much generation but our voltages are fairly consistent every day. Higher V than OPs though (no idea why that is), 260-280V. MPPT1 is east facing, MPPT2 is west facing.View attachment 13953

Your voltages fluctuate like one of mine. It seems from this graph you have Growatt like me so its interesting your graph is different to mine. How many panels do you have?

 

[Si_Oakwood]

Thanks for you reply. Theres no shading - both strings are identical in size and shape and are side by side. Similarly one string won't be any different in temperature to the other.


Your voltages fluctuate like one of mine. It seems from this graph you have Growatt like me so its interesting your graph is different to mine. How many panels do you have?

yes Growatt SPH3600, x7 450w panels on east side and same on west

 

[binky]

Hi all,

Would anyone who has a Growatt inverter have a look at their voltage trends for MPPT 1&2 please?
My system was installed on Monday and I've noticed a different trend for each string as shown below. The string with the maxed out 150v is producing less power than the other string. The strings seem to test out okay.

Any help appreciated.

Thanks,
View attachment 13950

Interesting! If the scaffold is still up:-

1/ I would check the MC4 connectors - shut down the DC before doing that, look for arcing on the contacts or the back of the MC4 not being done up properly, or a connector not pushed together properly. Don't normally get a problem with the factory fitted connectors, it tends to be the ones fitted for the DC runs back to the inverter by the installers.

2/ I would look at how clean the panels are, it's possible you have a panel with hand prints all over it / other dirt.

3/ it is also possibly a function of being limited to 3.6kW, ie one MPPT is being tweaked to limit max output?.

 

[73henny]

yes Growatt SPH3600, x7 450w panels on east side and same on west

I have 6 x 410w per string. It is odd there is such a difference in voltage between our systems?

Interesting! If the scaffold is still up:-

1/ I would check the MC4 connectors - shut down the DC before doing that, look for arcing on the contacts or the back of the MC4 not being done up properly, or a connector not pushed together properly. Don't normally get a problem with the factory fitted connectors, it tends to be the ones fitted for the DC runs back to the inverter by the installers.

2/ I would look at how clean the panels are, it's possible you have a panel with hand prints all over it / other dirt.

3/ it is also possibly a function of being limited to 3.6kW, ie one MPPT is being tweaked to limit max output?.

Scaffold is still up. Installer coming back tomorrow.

1) Will ask them to have a look at the connectors. It is interesting to me that the voltages are the same as the sun comes up and then move apart until the sun goes down? Almost like when the current gets above a certain level it is in some way restricted. Doesn't explain higher and seemingly fixed 150v though?

2) They all look clean and the same to me

3) I'd have though that it would only limit when the combined output was over 3.6kW. Theres a difference between the two strings even at low outputs.

 

[binky]

Kindly report what the installer says.

 

[73henny]

The installer returned today and swapped over the strings. PV1 stayed at 150v when the strings were swapped so the panels are okay. It looks like an inverter issue.
More investigation next week but it'll likely involve trying a replacement inverter.

 

[binky]

The installer returned today and swapped over the strings. PV1 stayed at 150v when the strings were swapped so the panels are okay. It looks like an inverter issue.
More investigation next week but it'll likely involve trying a replacement inverter.

Never did like Growatt. It's fair to say all makes of inverter seem to have had problems lately, I'm guessing this is down to COVID and demand for materials. Or it's just Chinese crap...

 

[73henny]

Never did like Growatt. It's fair to say all makes of inverter seem to have had problems lately, I'm guessing this is down to COVID and demand for materials. Or it's just Chinese crap...

Maybe. The installer hasn't had any issue with them up until now so has continued to use them.

 

[binky]

Maybe. The installer hasn't had any issue with them up until now so has continued to use them.

Their early inverters used to fail after 2years, along with some other cheap Chinese units, all failed with the same duff AC relay. I suspect they have improved, but I still don't like the spec, it's a bit basic.