Vmp is usually around 83% of Voc, so if your Vmp is above 425V, your Voc is above 500V.

On 2022/06/01 at 5:07 PM, YellowTapemeasure said:

Post a link to the panel's actual specs? It certainly sounds like you may be getting a little close to the the 500V limit. 

Reasons for getting less may be because of suboptimal azimuth and tilt. How are they installed? Also, what is your location?

@YellowTapemeasurepure truth , my tilt of only 18 degrees is killing me in midwinter. But I get a crazy powerfull yield in summer . So for my overall performance I look at a yearly average.  

Mine too.  I lose about 20% power in winter. In summer the system performs to spec. The chamge in angle of the sun makes a big difference for sure. No idea what my tilt is. I guess its around 20deg.

A "rule of thumb" for optimal panel tilt (both summer and winter) is to have the same degree of tilt as your latitude (0 degrees measured as parallel to level). I am in Midrand, Jhb, so my panels at 26 degrees is near enough (fortunately my roof pitch was good). For those in CT, around 34 degrees would be great.

Optimal tilt would be latitude + 15 degrees for winter and latitude -15 degrees in summer (and in-between these (therefore Latitude) for Autumn and Spring). There is fancy tilting kit available (that adjusts by 5 degrees each month), but for home installs, it is generally most economical to use static panels with optimal tilt for Autumn and Spring (hence the "rule of thumb", and make up any deficiencies by installing additional panels 😄 

19 minutes ago, YellowTapemeasure said:

A "rule of thumb" for optimal panel tilt (both summer and winter) is to have the same degree of tilt as your latitude (0 degrees measured as parallel to level).

21 minutes ago, YellowTapemeasure said:

Optimal tilt would be latitude + 15 degrees for winter and latitude -15 degrees in summer (and in-between these (therefore Latitude) for Autumn and Spring)

Good rule of thumb, to be considered in conjunction with rainfall & cloud cover patterns for your region. Tilting up in Winter might yield better results in Gauteng than Cape Town, and vice versa for tilting down.

The installer came back this morning, split the 1 string of 10 panels into 2 strings of 5, output is basically the same as before but voltage it much safer and within range. So my mind is more at ease now.

Tilt of the panels is basically that of a normal tile roof, not sure if I should mess around with the tilt and the possibly in summer the yield drops because of this?

Hi guys ! Hope you're doin'well. And hope you will light the bulb in my mind !

I have already 10 panel, 3500W, 1 string, installed. The panels are oriented SE ( i am in Europe).

The VoH stated on them it's 33.3 Volts, the Open Circuit Voltage it's 40.7 V.

Current 10.51A.

Linked to a 5.5KW hybrid inverter ( a clone, no name). Single MMPT. There is also a Pylontech usc2000 ( 2.4KW / 48V). Everything works ok. Inverter says max open circuit acceptable = 500 V.

MPPT interval between 120 to 450 V.

The Problem / Question

I would like to increase power production, i mean to mount more panels. I cannot find exactly SAME type of panels i got, what i found das a little bit different voltage., like :

Open Circuit Voltage(V) 40.9 V
Short Circuit Current(I) 10.89 A
Maximum Power Voltage(V) 33.8V
Maximum Power Current(I) 10.37 A

I would need more 6 panels, but i am not sure about wiring. There is a single MPPT. I need to do 2 strings, in parallel.

BUT...BUT....BUT... Is there a good idea to keep as it is  the actual string, and to put in parallel the new one, since there will be a difference in Voltage between strings ?

1. In other words, can one have 2 strings with different voltages ( and panel types) ? 

2. I can think about 2 strings x 8 panels each. But, this means the "new " string would have 6 (new) panels + 2 different panels ( old). And Voltage differs at panel level. Is this a good idea ? I've read somewhere that 5-10% difference in voltage it's acceptable.

What do you think ? Except a new inverter vith dual MPPT, which would be best choice...

 

On 2022/06/01 at 12:26 PM, Maverick said:

@RabidBunny do you know if the voltage limit on the Deye 8KW inverter of 425V is per MPPT or per string into the MPPT? As far as I understand each MPPT can take two strings of panels, does it combine this and then have a limit of 425V per string or total?

My system is a Deye 8KW with 10 panels of 455W which have a voltage of +-49V per panel all connected in series. So total voltage of +-490V, which come into a single MPPT via the + and - cables from the panels. So am I exceeding the MPPT tolerance? My max output is 3.6KW that I have seen. Which is far too little.

This was all done by an installer, I am not getting the desired output from my panels and thus I am now checking everything myself.

Thanks!

What I found from testing (and from previous answers here), is that the voltage limits (or recommendations) for the MPPT trackers are configured per MPPT and not per string, this means you can have two strings per MPPT both having their own voltages, as they are "combined" - ie. parallel - which causes the amp to rise.

Those voltage figures of yours are running concerningly close to the limits, one spike in PV Production (usually when cloudy and the sun peaks through on the edges of the cloud) and you fry your MPPT.

On 2022/06/01 at 12:26 PM, Maverick said:

@RabidBunny do you know if the voltage limit on the Deye 8KW inverter of 425V is per MPPT or per string into the MPPT? As far as I understand each MPPT can take two strings of panels, does it combine this and then have a limit of 425V per string or total?

My system is a Deye 8KW with 10 panels of 455W which have a voltage of +-49V per panel all connected in series. So total voltage of +-490V, which come into a single MPPT via the + and - cables from the panels. So am I exceeding the MPPT tolerance? My max output is 3.6KW that I have seen. Which is far too little.

This was all done by an installer, I am not getting the desired output from my panels and thus I am now checking everything myself.

Thanks!

Remember that the "MPPT Range" for the Deye 8kW Inverter I provided (125V ~ 425V), is not the limit it is the recommended range where your MPPT tracker will produce the best possible results ... (since you have the 8kW unit, you also should have 2 x MPPT's, where each can take 2 x Strings, ie. you can have 4 x Strings connected to your Inverter).

Since you are in Centurion, note that for your area your optimal azimuth is around 53 degrees during winter, and around 23 degrees in summer.

So regardless if your panels are facing 0 degrees north, you will also lose some efficiency if your azimuth is not correctly adjusted, begs the question who gets onto the roof to adjust the azimuth every 2 to 3 months ... ? (that's a little insane).

Take into account that the general average I've seen on the forums from much reading and asking is that people tend to lose about 30% efficiency during winter, which seems to be common in the Southern Hemisphere (even results from Australia, etc.).

If you need 100% optimal all-year-round, you will most likely need to install a sun-tracker system, which will cost more than your entire system, battery banks, panels, inverters all included, rather than just adding one or two odd panels to compensate for the loss.

Edited June 23, 20223 yr by RabidBunny

On 2022/06/03 at 3:35 PM, SolarNoobish said:

Hi guys ! Hope you're doin'well. And hope you will light the bulb in my mind !

I have already 10 panel, 3500W, 1 string, installed. The panels are oriented SE ( i am in Europe).

The VoH stated on them it's 33.3 Volts, the Open Circuit Voltage it's 40.7 V.

Current 10.51A.

Linked to a 5.5KW hybrid inverter ( a clone, no name). Single MMPT. There is also a Pylontech usc2000 ( 2.4KW / 48V). Everything works ok. Inverter says max open circuit acceptable = 500 V.

MPPT interval between 120 to 450 V.

The Problem / Question

I would like to increase power production, i mean to mount more panels. I cannot find exactly SAME type of panels i got, what i found das a little bit different voltage., like :

Open Circuit Voltage(V) 40.9 V
Short Circuit Current(I) 10.89 A
Maximum Power Voltage(V) 33.8V
Maximum Power Current(I) 10.37 A

I would need more 6 panels, but i am not sure about wiring. There is a single MPPT. I need to do 2 strings, in parallel.

BUT...BUT....BUT... Is there a good idea to keep as it is  the actual string, and to put in parallel the new one, since there will be a difference in Voltage between strings ?

1. In other words, can one have 2 strings with different voltages ( and panel types) ? 

2. I can think about 2 strings x 8 panels each. But, this means the "new " string would have 6 (new) panels + 2 different panels ( old). And Voltage differs at panel level. Is this a good idea ? I've read somewhere that 5-10% difference in voltage it's acceptable.

What do you think ? Except a new inverter vith dual MPPT, which would be best choice...

 

The 1st thing you need to check is the maximum current the MPPT can handle.

Place a picture here of your clone so that we can try and identify it. It might be possible that you cannot use 2 strings in parallel as it might exceed this current mentioned.

Those voltages are so close that if won't matter if they are used with your current panels. They can be in the same string as the old panels.  With your Voc max at 450V I would not run more than 10 in series if your inverter cannot use more than say 12A into the MPPT.

On 2022/04/19 at 8:00 AM, Thys van Niekerk said:

@RabidBunny

Would you mind sharing your wiring diagram 

 

Which sections are you interested the AC or DC side, or all?

 

Sorry have been very busy lately and haven't frequented the forums much.

On 2022/06/03 at 12:03 PM, YellowTapemeasure said:

A "rule of thumb" for optimal panel tilt (both summer and winter) is to have the same degree of tilt as your latitude (0 degrees measured as parallel to level). I am in Midrand, Jhb, so my panels at 26 degrees is near enough (fortunately my roof pitch was good). For those in CT, around 34 degrees would be great.

Optimal tilt would be latitude + 15 degrees for winter and latitude -15 degrees in summer (and in-between these (therefore Latitude) for Autumn and Spring). There is fancy tilting kit available (that adjusts by 5 degrees each month), but for home installs, it is generally most economical to use static panels with optimal tilt for Autumn and Spring (hence the "rule of thumb", and make up any deficiencies by installing additional panels 😄 

I tend to agree, if you adjust too much you will lose out in the other months ... rather just add the odd two or four panels to compensate.

 

I've had awesome results this summer that passed where I actually surpassed my PV array max capacity, I had 14.76kWp ... and generated around 15.5kW on most sunny days continuously.

 

I've since added a few more (as demand grew), and now have 19.76kWp ... (having generated just over 16kW peak yesterday - during winter).

 

My panels are all facing 18 degrees North-East, around a 8 degree tilt, so I'm thoroughly impressed by the panels, as my optimal tilt for winter is suppose to be 53 degrees and summer 23 degrees ...

On 2022/06/20 at 3:22 PM, Scorp007 said:

The 1st thing you need to check is the maximum current the MPPT can handle.

Place a picture here of your clone so that we can try and identify it. It might be possible that you cannot use 2 strings in parallel as it might exceed this current mentioned.

Those voltages are so close that if won't matter if they are used with your current panels. They can be in the same string as the old panels.  With your Voc max at 450V I would not run more than 10 in series if your inverter cannot use more than say 12A into the MPPT.

Not correct  @Scorp007 , the inverter controls the amperage that the panels are delivering to within it's max (22A) by increasing the resistance on the strings. They are well capable of controlling panels that are capable of generating more than 22A.  I am not sure what the limit of this is and I am sure that there is one but it is way above 22A. This is the same way that the inverter throttles the power production when the sun is out and you are generating more power than you are using and the battery fills up. The inverter throttles the production from the panels. 

The inverter cannot however control the Voltage and high voltages WILL fry the Mppt controllers.

The Sunsynk/DEYE 8kw inverters limits are 10400W of DC power and 8kw of AC power. 

I have 12.4Kw of panels and have had occasions where the inverter hits the max DC of 10.4kw.

I am using 455W JA Solar panels in a 6S2P & 8S2P configuration, generating 250V & 330V at the inverter respectively. 

Over watting the panels has the advantage of still generating good power on more overcast days although you will "loose" some of your power on high solar radiation days. Not really an issue in my life as in summer I have more power than I know what to do with and but needed more power in winter and on overcast days. It is very common in the UK to overspec the panels. 

On 2021/08/17 at 2:33 PM, RabidBunny said:

Hi Guys,

 

I've been reading up on many posts before and have studied the manuals from top-to-bottom ... but to-date I cannot find a "reasonable" answer as to the correct information I am seeking in terms of "PV Array / String Calculations" per MPPT Tracker [using multiple strings], etc.

 

I have the following setup:

 

2x Deye 8KW Hybrid Inverters ~ connected in parallel

24x 400W Mono Panels ~ strings are connected in series

 

Specifications for the Deye 8KW Hybrid Inverters:

Max. DC Input Power                     - 10400W
PV Input Voltage                            - 370V (100V~500V)
MPPT Range                                  - 125V ~ 425V
Start-up Voltage                            - 150V
PV Input Current                            - 22A + 22A
No. of MPPT Trackers                   - 2
No. of Strings Per MPPT Tracker - 2 + 2

 

Specifications for the 400W Mono Panels:

Maximum Power - Pmax (W)               - 400W
Positve Power Tolerance                     - 0 ~ +5W
Open Circuit Voltage - Voc (V)            - 49.76V
Short Circuit Current - Isc (A)              - 10.3A
Maximum Power Voltage - Vmpp (V)  - 41.19V
Maximum Power Current - Impp (A)    - 9.74A

Hi @RabidBunny

The double connections on the inverter to one MPPT controller are so that you don't have to use a string combiner connection, it combines the strings in parallel and the voltage on the two "strings" being combined needs to be the same. 

I assume that you only have the 24 panels connected to one inverter?  ie. 2 x 6S2P strings. 

Assuming you have the space on your roof you could just add an extra 4 x 400 panels onto each of the strings giving you 2 x  8S2P.

This would add 33% onto your daily production within the Max 10400W limit and would give you 12.8kw of panels

Another alternative would be to use the MPPT controllers on your second inverter and add another 1 or 2 strings onto it.

If so, you may want to consider an East/West split if possible to get more early morning and late afternoon energy.

@RabidBunny If you go and check the voltages on your current strings on the Solarman/Sunsynk website they should be under 300V if they are running in parallel which I highly suspect as they would be over voltage otherwise. 

On 2022/06/03 at 2:27 PM, Maverick said:

The installer came back this morning, split the 1 string of 10 panels into 2 strings of 5, output is basically the same as before but voltage it much safer and within range. So my mind is more at ease now.

Tilt of the panels is basically that of a normal tile roof, not sure if I should mess around with the tilt and the possibly in summer the yield drops because of this?

Wow @Maverick, so he had 10 Panels in series, you are lucky you didn't have a melted MPPT controller, that must have been pretty close to the limit!

Depending on what panels you have I would be tempted to combine your two strings of 5 into one parallel string, so a 5S2P configuration and use the other MPPT controller for some more panels when you have some cash. 

 

@Sc00bs

I'd be happy to be wrong. My answer was for a 5.5kw inverter and 1 x MPPT and you're answer relates to your 8kw unit with 2 MPPTs.

Is it possible that the inverter from @SolarNoobish

cannot use 22A into a MPPT and he only has 1 MPPT to work with for the 16 panels he intends fitting? It would have to be 2 strings in parallel.

Edited June 23, 20223 yr by Scorp007

1 hour ago, Sc00bs said:

Hi @RabidBunny

The double connections on the inverter to one MPPT controller are so that you don't have to use a string combiner connection, it combines the strings in parallel and the voltage on the two "strings" being combined needs to be the same. 

I assume that you only have the 24 panels connected to one inverter?  ie. 2 x 6S2P strings. 

Assuming you have the space on your roof you could just add an extra 4 x 400 panels onto each of the strings giving you 2 x  8S2P.

This would add 33% onto your daily production within the Max 10400W limit and would give you 12.8kw of panels

Another alternative would be to use the MPPT controllers on your second inverter and add another 1 or 2 strings onto it.

If so, you may want to consider an East/West split if possible to get more early morning and late afternoon energy.

The voltages does not have to be 100% the same for the MPPT's (I think there is a margin of tolerance).

I won't say 50V difference between them would be OK (you'll most likely get a unbalanced error/warning); but between 5 and 15 volts I'm pretty sure it would be OK?

Today was very bad weather and they ran around the 249V / 250V peak (each of the 4 x MPPT's, taking into account that they are "paralleled" - voltages roughly stay the same for the 2 x strings, but the amps double) ... on a good sunny day they push up to around the 300V mark.

I've added a few more panels since my original post, I started out with 24 x 410W panels and added another 12 x 410W panels (during summer), and then recently last week added another 12 x 415W panels.

I'm currently running 8 x Strings of 6 each (36 @ 410W 6S2P, 12 @ 415W 6S2P), I can still add 2 x panels per string and still be within the safe zone with regards to the 500V limits as I still have enough roof space 😀

Panels are facing 18 degrees North-East at a 8 to 10 degree tilt (I don't really have shading problems, even though I do have a lot of big trees, they are mostly far away not to cast shadows) ... (optimal tilt in summer is about 23 degrees and in winter around 53 degrees), but when I had 14.76kWp during summer I generated 15.5kWp on most of the sunny days.

Edited June 23, 20223 yr by RabidBunny

46 minutes ago, Sc00bs said:

@RabidBunny If you go and check the voltages on your current strings on the Solarman/Sunsynk website they should be under 300V if they are running in parallel which I highly suspect as they would be over voltage otherwise. 

The strings mostly run around the 300V (sunny days)

Edited June 23, 20223 yr by RabidBunny

59 minutes ago, Scorp007 said:

@Sc00bs

I'd be happy to be wrong. My answer was for a 5.5kw inverter and 1 x MPPT and you're answer relates to your 8kw unit with 2 MPPTs.

Is it possible that the inverter from @SolarNoobish

cannot use 22A into a MPPT and he only has 1 MPPT to work with for the 16 panels he intends fitting? It would have to be 2 strings in parallel.

Ahhh, I think we were cross threading there 🙂 

 

On 2022/06/02 at 11:58 PM, Scorp007 said:

I'm also in Cent with North facing panels. Your 3.6kw is a touch more than mine and pretty spot on for May. 31 May was a stand out day for the last few weeks. About a 10% higher peak and also a bit higher daily yield.

So nothing wrong with getting close to the 500V max but you never want to get 500V so a good call to split the 10 series.

Just a question, if the 10 panels are split into 2 series strings + then connected in paralel onto a single PV string on the inverter it will double the input Amps  - 10.89A x2 = 21,78A which is higher than the 22A max on the PV input? Is this correct?

On 2022/06/23 at 10:34 PM, Sc00bs said:

Not correct  @Scorp007 , the inverter controls the amperage that the panels are delivering to within it's max (22A) by increasing the resistance on the strings. They are well capable of controlling panels that are capable of generating more than 22A.  I am not sure what the limit of this is and I am sure that there is one but it is way above 22A.

Only saw this reply now.

Are we not saying the same thing. I mentioned the MPPT will determine the maximum current that the panels can provide. It was not stated that you cannot use panels that are capable of higher current.

If the Sunsynk has a maximum of 22A as per your example and you have seen a much higher current than that you are lucky as a number of members have found the PV to be throttled at a amp or 2 below this level. Perhaps to increase reliability.

38 minutes ago, J.c said:

Just a question, if the 10 panels are split into 2 series strings + then connected in paralel onto a single PV string on the inverter it will double the input Amps  - 10.89A x2 = 21,78A which is higher than the 22A max on the PV input? Is this correct?

Surely 21.78A is not higher than 22A?

do strings have to balanced.l eg on a 2 mppt inverter with 2 strings each can you do 12 +5 into 1 and say 10+5 on other?

 

do strings have to balanced.l eg on a 2 mppt inverter with 2 strings each can you do 12 +5 into 1 and say 10+5 on other?

Don't do that. If you put 2 strings in parallel onto one MPPT, they should have the same Voltage, or close to. The two MPPTs don't each have to have the same amount of panels in total.

What's your roof configuration, and why are you considering this specific setup? What panels and inverter are you talking about? Specs &/or model numbers?