Morning Everyone,

I installed a 12kw 3ph inverter along with 3 5kwh batteries and 11 panels (limited roof space) in 2023. No real issues and I tweaked the system to suit my preferences. We have a solar geyser so the whole house is on the inverter - what a pleasure! I do plan to split the board at a later stage but not a real priority now as I do not really use the UF heating.

The 12kw has 2 MPPT trackers with 1 MPPT having 2 strings. MPPT 1- (26A+13A), MPPT 2- 13A. PV input voltage is 160vdc - 800vdc, MPPT input voltage is 200vdc-650vdc.

I have 11x 545w 46,5Voc panels on MPPT1 String1 and wanted to add a couple more panels - easy I just added 3 panels to MPPT1 String2 to realise that this does not work - does one have to balance the 2 strings? The moment I switch them on String1 shows zero PV input from the 11 panels. It will also not work on MPPT2 as I have not reached minimum voltage.

I have limited roof space so my idea was to have 11panels and then 2 separate arrays of 3 and 4 panels.

Can one run 2 arrays in series with longer connection cables between the 2 arrays? I use 6mm sq.

I do not want to split the 11 panels into 2 arrays.

Shouls I maybe move the 11 panels to MPPT2 and connect the 2 seperate arrays to MPPT1 string 1 and 2 but will the 3 panels be enough to start the string on MPPT1?

Thanks

Pieter

  

Hi All, does anyone have some input for me on the above?

Thanks

Pieter

@Weimaraner  I do not know how many guys follow this partifcular topic/group in the forum but maybe move this post to another topic/group.

@Weimaraner I could be very wrong but it looks as if there may be 3 MPPT's but 2 of them are bridged (PV1) and therefore offer 26A and the other one is standalone (PV2) and is therefore 13A.

 

If you want to keep thing simple, change the strings.

PV1 = 10 panels

PV2 = 4 panels and can be expanded on later if you find space for additional panels. 4 panels should be fine to reach the start up voltage, worst case you may need to change this string to 5 panels if start up voltage is still an issue.

 

Alternatively, you could look at doing a single string of panels on PV2 and run them in parallel (7 panels in series then parallel them with the other 7 panels in series).

If the MPPT's are bridged for PV1, possibly even look at having "2" strings of 7 panels in series and connect the 7 panels to PV1 on both inputs to have them in parallel.

 

Keeping in mind you'd need to ensure the current is within the limit of the MPPT as well as the string voltage.

1 hour ago, Weimaraner said:

Hi All, does anyone have some input for me on the above?

at 46.5V per panel 3 panels would be 139.5V or thereabouts and your MPPT starts at 200V, so, ideally you need at lest 5 panels in series to come up to a voltage where the MPPT would function...

On 2024/02/13 at 8:54 AM, Weimaraner said:

Can one run 2 arrays in series with longer connection cables between the 2 arrays? I use 6mm sq.

yes, not ideal but the current is low-ish, so yes, you can do this...

 

On 2024/02/13 at 8:54 AM, Weimaraner said:

Shouls I maybe move the 11 panels to MPPT2 and connect the 2 seperate arrays to MPPT1 string 1 and 2 but will the 3 panels be enough to start the string on MPPT1?

no, see previous comment, 5 panels minimum to get above the MPPT start voltage...

also if you use MPPT1.1 and MPPT1.2 then number of panels for each of those strings should add up to the same voltage and it must be 200V or higher, but I'd personally cap it at 600V on the top end...

What's actually the layout of the roof? Where are the strings located, which way do they all face, and what's the biggest number of panels you can fit in each area?

4 hours ago, PsyCLown said:

@Weimaraner

PV1 = 10 panels

PV2 = 4 panels and can be expanded on later if you find space for additional panels. 4 panels should be fine to reach the start up voltage, worst case you may need to change this string to 5 panels if start up voltage is still an issue.

 

Alternatively, you could look at doing a single string of panels on PV2 and run them in parallel (7 panels in series then parallel them with the other 7 panels in series).

If the MPPT's are bridged for PV1, possibly even look at having "2" strings of 7 panels in series and connect the 7 panels to PV1 on both inputs to have them in parallel.

 

Keeping in mind you'd need to ensure the current is within the limit of the MPPT as well as the string voltage.

With a MPPT range from 200V up using 4 panels only on a string is looking for an unreliable string. As suggested the 5 panels could be the bare minimum. 

@Weimaraner Note that MPPT1 takes 2 parallel strings of 26A in total and not 26A+13A. The MPPT2 takes the 13A string. As @PsyCLown explained. 

Edited February 14, 20242 yr by Scorp007

11 hours ago, Scorp007 said:

With a MPPT range from 200V up using 4 panels only on a string is looking for an unreliable string. As suggested the 5 panels could be the bare minimum. 

@Weimaraner Note that MPPT1 takes 2 parallel strings of 26A in total and not 26A+13A. The MPPT2 takes the 13A string. As @PsyCLown explained. 

I saw 160v, but looking again I see voltage range is 200v to 650v - however the line above has the range as 160v to 650v.

Definitely want at least 5 panels if 200v is required to start up and use the MPPT.

Edited February 15, 20242 yr by PsyCLown