Hi,

I've started a second string on my inverter roughly a month ago, it was performing well until a week or so ago. It is not producing as supposed, it drops in output during the peak time. Current  fluctuates constantly. 

Inverter: Sunsynk 5kw

String 2: 3x 540W JA Solar Mono PERC

Panels are clean, get 0% Shading

What could be the cause?

Thanks

11 minutes ago, paulw said:

Hi,

I've started a second string on my inverter roughly a month ago, it was performing well until a week or so ago. It is not producing as supposed, it drops in output during the peak time. Current  fluctuates constantly. 

Inverter: Sunsynk 5kw

String 2: 3x 540W JA Solar Mono PERC

Panels are clean, get 0% Shading

What could be the cause?

Thanks

3 in series does not give enough volts for the MPPT to work. When it's colder the panels reach enough volts. During peak being warmer it drops. Add another similar panel in each string

Or

Add these 3 in series with the 3 in string 1 if they face the same direction and angle.

Edited July 12, 20224 yr by Scorp007

3 minutes ago, Scorp007 said:

3 in series does not give enough volts for the MPPT to work. When it's colder the panels reach enough volts. During peak being warmer it drops. Add another similar panel.

How many of these panels are on string 1?

String 1 has 4x 340w, voltage is pritty similar with the 4 panels on string 1 as with the 3x 540w on string 2. Cannot see how this can be the problem as it worked fine. You can see on the graphs for string 2 the power output is way lower than that of string 1 and the current fluctuates constantly. Maybe saying drops in and out as original post is a bit confusing

20 minutes ago, paulw said:

String 1 has 4x 340w, voltage is pritty similar with the 4 panels on string 1 as with the 3x 540w on string 2. Cannot see how this can be the problem as it worked fine. You can see on the graphs for string 2 the power output is way lower than that of string 1 and the current fluctuates constantly. Maybe saying drops in and out as original post is a bit confusing

If you are sure your 3 panels provide the 150V needed then ignore what I thought the problem is. Refer to the minimum voltage the Sunsynk needs.

My calculations indicate your 3x540W panels are at 20V less than the other 4.

Edited July 12, 20224 yr by Scorp007

4 minutes ago, Scorp007 said:

If you are sure your 3 panels provide the 150V needed then ignore what I thought the problem is. Refer to the minimum voltage the Sunsynk needs.

As per my understanding, Startup Voltage is irrelevant if the Inverter has batteries connected. Maybe someone else can confirm or explain? Looking at the same datasheet you attached, Sunsynk also show MPPT range as between 125-425V. Also, wouldn't the current "as per graph" go to 0A thus switching completely off if undervoltaged?

57 minutes ago, paulw said:

As per my understanding, Startup Voltage is irrelevant if the Inverter has batteries connected. Maybe someone else can confirm or explain? Looking at the same datasheet you attached, Sunsynk also show MPPT range as between 125-425V. Also, wouldn't the current "as per graph" go to 0A thus switching completely off if undervoltaged?

I cannot confirm but would guess that at times you are also not even getting the 125V needed as the Vmpp for 3 panels in summer time would be 124V. My guess is these panels have a Vmpp=41.5V. You are indeed working on the edge of working or not. A sure area where things can go hay wire.

Only if you provide the graph showing the actual voltage on the string can one say yes/no.

6 minutes ago, Scorp007 said:

I cannot confirm but would guess that at times you are also not even getting the 125V needed as the Vmpp for 3 panels in summer time would be 124V. My guess is these panels have a Vmpp=41.5V. You are indeed working on the edge of working or not. A sure area where things can go hay wire.

Only if you provide the graph showing the actual voltage on the string can one say yes/no.

It makes sense wat you saying, see string voltages

44 minutes ago, paulw said:

It makes sense wat you saying, see string voltages

I would still say the moment the string 2 tries to get the MPP of the panels the voltage starts dropping and to continue working it loads the panels at a lower amps - read Watts to keep above the 125V. Graphs not on an clear scale but again I say it's around 125V. Sometimes we create our own problems and I think running at 125-133V as you are doing might be one of those times.

Why not all 7 in series?

Edited July 12, 20224 yr by Scorp007

5 minutes ago, Scorp007 said:

I would still say the moment the string 2 tries to get the MPP of the panels the voltage starts dropping and to continue working it loads the panels at a lower amps - read Watts to keep above the 125V. Graphs not on an clear scale but again I say it's around 125V. Sometimes we create our own problems and I think running at 125-133V as you are doing might be one of those times.

Why not all 7 in series?

 They are completely different spec, 340W Poly Canadians vs. 540 W JA MONO PERC's. I will add another 540W to string 2 and see what it does, the plan was to expand on it anyways, now's the time it seems. Hopefully the extra panel's volts it will stabilize the string. I will update when it is done.

Thanks for the help

 

6 minutes ago, paulw said:

 They are completely different spec, 340W Poly Canadians vs. 540 W JA MONO PERC's. I will add another 540W to string 2 and see what it does, the plan was to expand on it anyways, now's the time it seems. Hopefully the extra panel's volts it will stabilize the string. I will update when it is done.

Thanks for the help

 

Now your talking. I guess sacrificing less than 2 amps power in winter when running in 1x7S is a much better option than what you have done with 4xS plus 3xS in 2nd string.