So I have a strange question..

Currently I have 12 330watt Canadians on my roof. These are running through a Victron 150/100 mppt in 4 strings of 3. Canadians have a VOC of around 40v if I recall correctly. So in theory its around 120V voc. I am starting to desire more power during the day as my consumption is going up with AC's etc in the house. Anyways. I want to replace my panels with 550watt panels. Can get Longis for a good price. The Longis however have a 49v VOC making 3 in series x 4 a no go as it is maxing out the MPPT on VOC and will definately cross the threshold on a cold morning. There are thus then two options.. I buy 12 panels and have 6 strings of two panels. I dont like this as at best I will have around 80v operational which is rather low...  Or I buy 9 longis and run 4 strings. Each string two longi's and one Canadian which will make VOC around 140v. I have been advised perhaps not a good idea...  What do you guys think? The only alternative is buying a 250/100 and just run 3 strings of 4. But did not really want to spend that on top.

3 hours ago, JTK said:

So I have a strange question..

Currently I have 12 330watt Canadians on my roof. These are running through a Victron 150/100 mppt in 4 strings of 3. Canadians have a VOC of around 40v if I recall correctly. So in theory its around 120V voc. I am starting to desire more power during the day as my consumption is going up with AC's etc in the house. Anyways. I want to replace my panels with 550watt panels. Can get Longis for a good price. The Longis however have a 49v VOC making 3 in series x 4 a no go as it is maxing out the MPPT on VOC and will definately cross the threshold on a cold morning. There are thus then two options.. I buy 12 panels and have 6 strings of two panels. I dont like this as at best I will have around 80v operational which is rather low...  Or I buy 9 longis and run 4 strings. Each string two longi's and one Canadian which will make VOC around 140v. I have been advised perhaps not a good idea...  What do you guys think? The only alternative is buying a 250/100 and just run 3 strings of 4. But did not really want to spend that on top.

The series option of 550 and 330W is a no go. The 330W will throttle the 550W to the current of the 330W panels. 

Those that know the Victron system might weigh in. May be a seperate MPPT for new panels? 

Secondhand panels won't bring in a lot of money currently. I would just buy an additional MPPT en connect the new panels to them.

so this still leaves the question. 6 strings of 2x550 panels worth it on a 150/100. getting a 250/100 will add R10k to the bill...

 

ps: no space for more than 12 panels on the roof. which there was else keeping would be a no brainer

Edited November 15, 20232 yr by JTK

8 hours ago, JTK said:

so this still leaves the question. 6 strings of 2x550 panels worth it on a 150/100. getting a 250/100 will add R10k to the bill...

 

ps: no space for more than 12 panels on the roof. which there was else keeping would be a no brainer

You can use up to 8x550W panels before you reach the maximum of the 150/100. However as the temp of the 150/100 increases it might throttle the PV. 

The 250/100 can also only charge up to 100A to the battery. The only plus is you can use 4 panels in series and use 2 strings instead of 4. Less cable. 

Edited November 15, 20232 yr by Scorp007

On 2023/11/14 at 2:07 PM, Scorp007 said:

The series option of 550 and 330W is a no go. The 330W will throttle the 550W to the current of the 330W panels. 

This is not entirely accurate, if the 550 and the 330 have the same or very close to the same Isc and Imp, then you can happily series them... the lower of the current specs will be the limit of current flowing, thus a Voltage mix like this can work, but the current must be close to the same, else you would have larger losses...

 

On 2023/11/14 at 10:15 AM, JTK said:

I dont like this as at best I will have around 80v operational which is rather low... 

Ok, why? I would think the Victron 150/100 mppt feeds a 48-Volt-ish battery, so what would the problem be with 80V and higher Amperes?

1 hour ago, Kalahari Meerkat said:

This is not entirely accurate, if the 550 and the 330 have the same or very close to the same Isc and Imp, then you can happily series them... the lower of the current specs will be the limit of current flowing, thus a Voltage mix like this can work, but the current must be close to the same, else you would have larger losses...

 

You are correct. The problem I have found is that you normally can't find 330W panels at a current of 13-14A which is the going value for 550W panels. 330W are around 9.5-10A. 

On the other hand if you can find 550W panels with a current that matches the existing panels then no loss as I tried to alert to. 

The devil is in the detail and one would need to know the current of the 330W panels installed at the moment. 

2 hours ago, Kalahari Meerkat said:

Ok, why? I would think the Victron 150/100 mppt feeds a 48-Volt-ish battery, so what would the problem be with 80V and higher Amperes?

The limitation is the 100A current the 150/100 can provide. You cannot just input 80-150V and expert the current can exceed the value of 100.

Check the specs for the MPPT. That is how ALL Victron MPPTs are coded. Max Voltage/Amps output. 

13 hours ago, Scorp007 said:

The limitation is the 100A current the 150/100 can provide. You cannot just input 80-150V and expert the current can exceed the value of 100.

Check the specs for the MPPT. That is how ALL Victron MPPTs are coded. Max Voltage/Amps output. 

Ok, I see 150Voc max for the panels and 100A max charge current, at 50-odd Volt, that would be 5kW... at 80V from the panels, you'd need to provide 65A, or thereabouts, so I am definitely not understanding the problem, other than providing 65A from the solar panel side would require quite a bit of copper cabling to cater for this current... what am I missing?

Edited November 16, 20232 yr by Kalahari Meerkat

5 hours ago, Kalahari Meerkat said:

Ok, I see 150Voc max for the panels and 100A max charge current, at 50-odd Volt, that would be 5kW... at 80V from the panels, you'd need to provide 65A, or thereabouts, so I am definitely not understanding the problem, other than providing 65A from the solar panel side would require quite a bit of copper cabling to cater for this current... what am I missing?

I don't know how can I explain it. Sorry. You can provide up to 150Vx65A to the MPPT. 9759W. The MPPT can only output(use) 58x100A. Thus the MPPT will not be able to use 65A at 150V. At 80V it can use up to 72.5A.

Should you go for the 250/100 you can input up to 250V and still only 100Ax58-5800W to the battery. 

Refer to the pictures. The top line is the power to the battery. The bottom line is the maximum power for charging to 48V.

This for the mentioned application a waste of money to think a 250/100 is an upgrade 

2 hours ago, Scorp007 said:

This for the mentioned application a waste of money to think a 250/100 is an upgrade 

Ok, yes, but the 80V is not a problem, if you can provide 65A at 80V, then your MPPT should, provide, roughly 5200W at 50V to the battery, since the xxx/100 is limiting the battery end to 100A, this is also only 5kW app. max DC out, thus there's no point in thinking it an "upgrade", then only thing it will allow is higher PV voltages but therefore less current, like 20A or so, this will save on copper between the panels and the MPPT, but do nothing more, that I can think of.

Basically the limitation is the xxx/100, he can add second one, if there more of a requirement for higher current on the 48V/battery side, but the 80V on solar panel end is not a limitation, only requires thicker cabling, since the current there would be higher than if he could run 200-odd volt instead... since he already has the 150/100, I'd assume the cabling from the solar panels is already appropriately sized and if he needs more panels, then more cabling is also implied...

thanks guys. yes it will work but its not ideal. Even victron's spreadsheet recons I cant go more than 10 panels with the 150/100. Anyways. there is still some time

On 2023/11/14 at 10:15 AM, JTK said:

So I have a strange question..

Currently I have 12 330watt Canadians on my roof. These are running through a Victron 150/100 mppt in 4 strings of 3. Canadians have a VOC of around 40v if I recall correctly. So in theory its around 120V voc. I am starting to desire more power during the day as my consumption is going up with AC's etc in the house. Anyways. I want to replace my panels with 550watt panels. Can get Longis for a good price. The Longis however have a 49v VOC making 3 in series x 4 a no go as it is maxing out the MPPT on VOC and will definately cross the threshold on a cold morning. There are thus then two options.. I buy 12 panels and have 6 strings of two panels. I dont like this as at best I will have around 80v operational which is rather low...  Or I buy 9 longis and run 4 strings. Each string two longi's and one Canadian which will make VOC around 140v. I have been advised perhaps not a good idea...  What do you guys think? The only alternative is buying a 250/100 and just run 3 strings of 4. But did not really want to spend that on top.

To be checked. Is it not possible at all to fit a new 330W panel, or anything of similar or even slightly higher output? The thinking would be to arrange the existing panels firstly in a 2s6p setup, and then add only 6 panels, one new panel onto each string of 2 older Canadians, to end up with 3s6p. Something like the JA Solar panel below, not saying it's the best matching solution size-wise or colour-wise, just an example of a panel with a 41.3Voc and 10.8A Imp, ie. slightly higher than the existing panels.

JA Solar MBB Half-Cell Black Module 120 cell 370w Mono PV Module for Sale Online (herholdts.co.za)

Cost-wise one might get 550W panels at a better Rand/W, but in this way you might get away spending less money, and still ending with a setup having Voc around 120-125V, and Imp around 60-65A, and approx 6200W of connected panel power, on the same old MPPT.

Edited November 20, 20232 yr by GreenFields

On 2023/11/20 at 11:03 AM, GreenFields said:

To be checked. Is it not possible at all to fit a new 330W panel, or anything of similar or even slightly higher output? The thinking would be to arrange the existing panels firstly in a 2s6p setup, and then add only 6 panels, one new panel onto each string of 2 older Canadians, to end up with 3s6p. Something like the JA Solar panel below, not saying it's the best matching solution size-wise or colour-wise, just an example of a panel with a 41.3Voc and 10.8A Imp, ie. slightly higher than the existing panels.

JA Solar MBB Half-Cell Black Module 120 cell 370w Mono PV Module for Sale Online (herholdts.co.za)

Cost-wise one might get 550W panels at a better Rand/W, but in this way you might get away spending less money, and still ending with a setup having Voc around 120-125V, and Imp around 60-65A, and approx 6200W of connected panel power, on the same old MPPT.

The only problem is the MPPT can only use 48x100A for charging the battery. Victron are known to throttle the 100A output as soon as the temp goes up 

6200W will only come into their own right in winter and cloudy days. 

Overall a very good suggestion on panel use but seems there is not space for 18.