Hi!

I have a Voltronic Axpert VM III with a string of 8 Jinko panels (JKM330PP-72-V Vmp=37.8v Imp=8.74A) working for 6 years flawless. They get as high as 320v.

My inversor has a label where is said that max FV is 4000w, and 500v (label attached)

I want to increase the number of panels to have more energy before and after midday. The panels I can buy nowdays are:

• JAM54D41-LB 440W Vmp=32.47, Imp=13.55A

• JAM72S30 LR 565W Vmp=41.68v, Imp=13.56A

My first though was make a second string with 7 (to get the most similar voltage) with 565W panels, but I will have very different intensity in each series, 8.74A vs 13.56A, which will generate in some hours of the day very much if 4000w (the max of the MPPT).

1. Is there any problem on having two strings (parallel connected) with so different intensity?

2. Is too much wattage for MPPT? Any experience overpaneling VM III?

3. Will you recommend me any other combination?

PS: I have a US5000 battery connected to VM III in Pylon mode, and probably I will add another US5000 soon

Edited March 21, 20251 yr by TomasCrespo
Typos

9 minutes ago, TomasCrespo said:

Hi!

I have a Voltronic Axpert VM III with 8 Jinko panels (JKM330PP-72-V) in serial for 6 years working flawless. They get as high as 320v.

My inversor has a label where it is said tah max FV is 4000w, and 500v (label attached)

I want to increase the number of panels to have more energy before and after midday. The panels I can buy nowdays are:

No information displays of the panels you can buy.

4 minutes ago, Scorp007 said:

No information displays of the panels you can buy.

Sorry. Fixed.

The factor with which you over panel the inverter is far too high for my liking. The MPPT is rated for 4kW and the new 565x7 panels is already just below the maximum.

Yes as the 2 string will be in parallel you need to get to get the voltage close as you have with this combination.

In your position without upgrading the inverter it seems you can get 1.2kW more by replacing the current 8x330W with the 7x565W. You can also use up to 9x565W for a 20% over panel which is normally OK. This would give you an output in line with 1000W/m² if the irradiance is 800W/m². Area dependent.

1 hour ago, Scorp007 said:

The factor with which you over panel the inverter is far too high for my liking. The MPPT is rated for 4kW and the new 565x7 panels is already just below the maximum.

Yes as the 2 string will be in parallel you need to get to get the voltage close as you have with this combination.

In your position without upgrading the inverter it seems you can get 1.2kW more by replacing the current 8x330W with the 7x565W. You can also use up to 9x565W for a 20% over panel which is normally OK. This would give you an output in line with 1000W/m² if the irradiance is 800W/m². Area dependent.

Thanks for the info.

I know voltage of two strings must be very similar, but my question is about amperage. Could be significant differences in amperage of each parallel string?

Any other option keeping old panels? What do you think about two strings with different orientation? Old string is south. I could create a new string facing southwest. They will never get 4000w, isn't it?

Would be possible using a secondary MPPT with this setup (VM III with integrated MPPT and pylontech batteries)?

Edited March 22, 20251 yr by TomasCrespo

12 minutes ago, TomasCrespo said:

Thanks for the info.

I know voltage of two strings must be very similar, but my question is about amperage. Could be significant differences in amperage of each parallel string?

Any other option keeping old panels? What do you think about two strings with different orientation? Old string is south. I could create a new string facing southwest. They will never get 4000w, isn't it?

If you have strings in parallel like you might do each will operate at their own current. The picture you place does not indicate what the maximum current input of the MPPT is. But combining your proposed panels is not something I will do for reasons mentioned about over panelling as much as the 565W would cause.

I take it you are in the northern hemisphere?

8 minutes ago, TomasCrespo said:

Thanks for the info.

I know voltage of two strings must be very similar, but my question is about amperage. Could be significant differences in amperage of each parallel string?

Any other option keeping old panels?

If the Voltages are equal, then the sum of the current of the two strings in parallel will be fed into the MPPT. The link below has some thoughts on the Axpert King's MPPT input.

21 minutes ago, TomasCrespo said:

Any other option keeping old panels?

Would it be an option to get a new dual-MPPT inverter? Something like the Luxpower SNA5000, or a hybrid inverter like a Deye or Solis 5kW? You could keep your existing string for the first MPPT, and add 5 or 6 of the 565W panels on MPPT2, and you would still be below the inverter's 6000W PV power limit (or greater depending on inverter), and it wouldn't even be considered over-panelling. Considering that you're aiming to add a 2nd Pylontech 5kWh battery, this could be a better balance between configuration of panels, MPPT power generation, and storage.

42 minutes ago, Scorp007 said:

If you have strings in parallel like you might do each will operate at their own current. The picture you place does not indicate what the maximum current input of the MPPT is. But combining your proposed panels is not something I will do for reasons mentioned about over panelling as much as the 565W would cause.

I take it you are in the northern hemisphere?

I am in Murcia, Spain.

Not with 565W panels, but with 7x440W?

32 minutes ago, GreenFields said:

If the Voltages are equal, then the sum of the current of the two strings in parallel will be fed into the MPPT. The link below has some thoughts on the Axpert King's MPPT input.

I know, but I do not know if very different amperage could be a problem, i.e. a string with 8.1 A and another string with 14A.

32 minutes ago, GreenFields said:

Would it be an option to get a new dual-MPPT inverter? Something like the Luxpower SNA5000, or a hybrid inverter like a Deye or Solis 5kW? You could keep your existing string for the first MPPT, and add 5 or 6 of the 565W panels on MPPT2, and you would still be below the inverter's 6000W PV power limit (or greater depending on inverter), and it wouldn't even be considered over-panelling. Considering that you're aiming to add a 2nd Pylontech 5kWh battery, this could be a better balance between configuration of panels, MPPT power generation, and storage.

Replacing the inverter is not an option (unless VM III die). Currently I have almost all the energy I need. It's a small off-grid country house and the loads are the pump of a swiming pool and an air conditioner (about 1000W each one), so I only need a bit more watts to keep the two loads working at the same time (and the battery loading). But once I redesigning the installation... I would like to get more power earlier in the morning and/or late in the afternoon (and cloudy days).