Solar input problems (50% capacity) using Growatt’s builtin MPPT charger with 4 panels (2s,2p)

[MichelT]

System:
4 solar panels, 44V 8A each (approximatively) with shade
Growatt 120V 3kWh inverter with MPPT solar input limited to 115V, 60A
LiFePo4 battery 7kwh (8 cells in series)
Note: I want to control the Max voltage of the battery charging (usually around 27V, but I want to be able to change that).
Note: The growatt does allow me to do this, but the solution I seek must also allow this.

Panels:
series #1; + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
series #2: + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
then
series #1 in parallel with series #2 for a Total = 88V x 16A (1.4kw)

Location:
This is installed on the top of a patio cover of a house rental.
Panels are exposed to a small amount of shade
(shade is NOT the issue, but the variable power output that they cause is).

Problem:
Panels are connected over the patio cover and produces 2 wires in output (simple).
But the Growatt MPPT internal charger seems to struggle at deciding what voltage and amps to optimize its power generation.
=> The result is that the power it generates (Growatt) fluctuates greatly from about 450W to 1400W when fully exposed to sun (no cloud, no shade).

IMPORTANT
Apr09 additional detail: When I disconnect 1 of the 2 parallel connection, then I get stable power production (about 600W).
Apr09 additional detail: When I disconnect the other parallel connection, then I get stable power production (about 600W).
Apr09 additional detail: When I disconnect BOTH parallel connection, then I get usually about 600W (sometimes it goes up to 700 to 1000W)

If I disconnect and reconnect a panel or a series, the Growatt ‘figures it out‘ and suddenly changes its production to random outputs;
either to any output between 450W to 1400W (at random) and stays there (it varies only by a few watts).

What I think is going on:
The Growatt MPPT, tries different voltages (and amps). Because each panel series are not exactly the same,
the power of one series can go through the following possible scenarios. Examples;
1) series #1 may product 90V, the other (series #2) 80V, this causes 90V wanting to get into the 80V (because they are connected in parallel),
but the 80V series blocks it using its diode. Result = only 1 series produce (about 700W)
2) or sometimes, both voltages kind of matches and 2 series produce (about 1400W)
3) sometimes (more rarely like 15% of the time, I get about 900W, perhaps because 1 panel could have some shade???)

What I think could solve the problem:
1) If I could regulate the voltage of each panel, using perhaps a charge controller per panel, or a buck converter,
then I am guessing the output of each panel could be added in parallel since they would all be the same voltage (ex: 24V, or 48V, or 44V, etc.)
this would therefore add all currents and the power would add up (to 1400W in full sun).
Then I would give the resulting power to the Growatt which would control the battery charging and inverter.
QUESTION: Is there such ’Per Panel Power Regulator’ I could put under each panel? Which brand? which one I should buy? any ebay link?

2) or I could bring each panel wires (4x2 wires) down to a centralized Charge Controller which would allow 4 solar panel inputs and then produce
a single output which would charge the batteries (which would feed the Growatt which at this point would not have any inputs in its solar panel socket).
QUESTION: Is this the best way to resolve my power issue? Is there such a charge controller? Is it a Renogy? Which model? any ebay link?

3) or perhaps there is something else I do not understand or don’t know??
QUESTION: How do I resolve this power issue? I would like maximum power output which would adapt if any panel gets any kind of shade
with the minimum cost while being safe, simple and reliable.

This is my first solar system. I am an electric engineer, but I have near no experience with solar systems and shade on panels.

I really want my system to work, please please someone help me and I will be very very greatful ?

Michel

 

[snoobler]

Welcome to the forum.

Problem:
Panels are connected over the patio cover and produces 2 wires in output (simple).
But the Growatt MPPT internal charger seems to struggle at deciding what voltage and amps to optimize its power generation.
=> The result is that the power it generates (Growatt) fluctuates greatly from about 450W to 1400W when fully exposed to sun (no cloud, no shade).

If I disconnect and reconnect a panel or a series, the Growatt ‘figures it out‘ and suddenly changes its production to random outputs;
either to any output between 450W to 1400W (at random) and stays there (it varies only by a few watts).

To confirm, you have a 2S2P array wired into the single MPPT input.

How are they wired together in parallel?

Have you confirmed that all connections are secure?

Have you confirmed all 4 individual panel's Voc and Isc are within spec and highly similar?

What I think is going on:
The Growatt MPPT, tries different voltages (and amps). Because each panel series are not exactly the same,
the power of one series can go through the following possible scenarios. Examples;
1) series #1 may product 90V, the other (series #2) 80V, this causes 90V wanting to get into the 80V (because they are connected in parallel),
but the 80V series blocks it using its diode. Result = only 1 series produce (about 700W)
2) or sometimes, both voltages kind of matches and 2 series produce (about 1400W)
3) sometimes (more rarely like 15% of the time, I get about 900W, perhaps because 1 panel could have some shade???)

In full sun conditions, a properly functioning system should not behave this way. You have a problem with a panel, a connection, a component in the circuit (fuse/breaker) or the MPPT isn't functioning properly.

A single shaded cell on a panel can reduce that panel's output by 1/3, so shading behavior can be pretty wonky, but a properly functioning MPPT should be fairly steady for a given shading mostly static scenario. If the shade is from trees blowing in the wind, that will wreak havoc on the array and output will be very inconsistent.

What I think could solve the problem:
1) If I could regulate the voltage of each panel, using perhaps a charge controller per panel, or a buck converter,
then I am guessing the output of each panel could be added in parallel since they would all be the same voltage (ex: 24V, or 48V, or 44V, etc.)
this would therefore add all currents and the power would add up (to 1400W in full sun).
Then I would give the resulting power to the Growatt which would control the battery charging and inverter.
QUESTION: Is there such ’Per Panel Power Regulator’ I could put under each panel? Which brand? which one I should buy? any ebay link?

2) or I could bring each panel wires (4x2 wires) down to a centralized Charge Controller which would allow 4 solar panel inputs and then produce
a single output which would charge the batteries (which would feed the Growatt which at this point would not have any inputs in its solar panel socket).
QUESTION: Is this the best way to resolve my power issue? Is there such a charge controller? Is it a Renogy? Which model? any ebay link?

3) or perhaps there is something else I do not understand or don’t know??
QUESTION: How do I resolve this power issue? I would like maximum power output which would adapt if any panel gets any kind of shade
with the minimum cost while being safe, simple and reliable.

There are optimizers for about $50 that will likely help, but all 3 options above should not be necessary. Something is not working properly, and the root cause should be identified and corrected. Again, bad panel, connection, component or the MPPT itself.

if you got this from Ian at watts247.com, I would reach out to him after you've checked all your connections/components.

This is my first solar system. I am an electric engineer, but I have near no experience with solar systems and shade on panels.

I really want my system to work, please please someone help me and I will be very very greatful ?

Michel

Ah. engineer. That makes sense. Our problem solving skills are too developed, and we often miss the simple stuff and over-analyze...

Something is broken. Start at each panel, confirm specs. Confirm each connection is good, etc. You may find a bad MC4 connector or high resistance connection (parallel bridge connector) that works fine in its own string but muddies the works when working in parallel.

Lastly, keep in mind that you're working with Chinese made hardware that is dramatically cheaper than the more reputable brands. Blind faith in their operation isn't generally warranted.

 

[MichelT]

Welcome to the forum.



To confirm, you have a 2S2P array wired into the single MPPT input.

How are they wired together in parallel?

Panels:
series #1; + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
series #2: + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
then
series #1 in parallel with series #2 for a Total = 88V x 16A (1.4kw)

Have you confirmed that all connections are secure?

yes

Have you confirmed all 4 individual panel's Voc and Isc are within spec and highly similar?

yes

In full sun conditions, a properly functioning system should not behave this way. You have a problem with a panel, a connection, a component in the circuit (fuse/breaker) or the MPPT isn't functioning properly.

A single shaded cell on a panel can reduce that panel's output by 1/3, so shading behavior can be pretty wonky, but a properly functioning MPPT should be fairly steady for a given shading mostly static scenario. If the shade is from trees blowing in the wind, that will wreak havoc on the array and output will be very inconsistent.


There are optimizers for about $50 that will likely help, but all 3 options above should not be necessary. Something is not working properly, and the root cause should be identified and corrected. Again, bad panel, connection, component or the MPPT itself.

if you got this from Ian at watts247.com, I would reach out to him after you've checked all your connections/components.




Ah. engineer. That makes sense. Our problem solving skills are too developed, and we often miss the simple stuff and over-analyze...

Something is broken. Start at each panel, confirm specs. Confirm each connection is good, etc. You may find a bad MC4 connector or high resistance connection (parallel bridge connector) that works fine in its own string but muddies the works when working in parallel.

Lastly, keep in mind that you're working with Chinese made hardware that is dramatically cheaper than the more reputable brands. Blind faith in their operation isn't generally warranted.

 

[snoobler]

How are they paralleled?

Do you have overcurrent protection in each string?

Do you have a breaker or switch in each string?

Did you get the AiO from Watts247.com (assuming you're U.S. based)?

 

[MichelT]

How are they paralleled?

Panels:
series #1; + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
series #2: + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
then
series #1 in parallel with series #2 for a Total = 88V x 16A (1.4kw)

Do you have overcurrent protection in each string?

No

Do you have a breaker or switch in each string?

No

Did you get the AiO from Watts247.com (assuming you're U.S. based)?

Is this some kind of solicitation? What is an AiO ? Why do you suggest Watts247.com ?

 

[snoobler]

Panels:
series #1; + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
series #2: + [ panel 44V, 8A ] - + [ panel 44V, 8A ] - == [ 88V, 8A ]
then
series #1 in parallel with series #2 for a Total = 88V x 16A (1.4kw)

Repeating that they are in parallel does not tell me HOW you have them paralleled.

HOW are the parallel connections made?

Is this some kind of solicitation? What is an AiO ? Why do you suggest Watts247.com ?

AiO = All in One.

watts247.com is the ONLY U.S. distributor for MPP Solar/Growatt. They offer excellent product support. If you purchased from there, they will provide support.

 

[MichelT]

I thought I described how they are connected in parallel,
Do you mean what kind of wires?
After they are in parallel, they go to the Growatt AiO inverter. Perhaps this is what you wanted to know?
I am not sure what you mean by how, do you want a diagram that will match my wordings???

Once they are in parallel, I get 2 wires gauge 10 Awg. Those 2 wires go through a 20A double breaker.
I will try attaching a photo of the breaker. Then I go directly in the Growatt inverter which has and uses its internal MPPT charger which them goes to the batteries.

 

[HRTKD]

What he wants to know is what adapter are you using to get the two series strings into parallel. Are you using an MC4 Y adapter?

 

[MichelT]

Problem solved: The Growatt inverter was programmed to limit the charging voltage to 3.35 volt per cell.
When charging was reaching this voltage, it was reducing the power (amps).
Stupid problem !??