Solar panels in series

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Hello everyone.

I have 10 solar panels rated 45V DC (450 vdc), 9 amp connected in series.

These 2 wires from terrace go to an inverter in basement. There is no battery storage. Whatever is produced, goes back to local power company and they provide discount
(Units sent to them)

Presently, I am falling short of 2 panels as per my consumption, so purchased 2 new.

After purchasing, i realised that 12 in series (45x12) will cross 500 max V of inverter.

Can I connect in parallel? Lot of amp left as per inverter specs.

Below are pics of specs of inverter and panel.

PS: On google i read that inverter will use lowest ampere of all when connected in parallel. I dont understand this part.

How to use all 12 panels with full efficiency?

Thank you.

Files attached.
 

Attachments

Deleted member 440916

Joined Dec 31, 1969
0
Unfortunately as VOC of your panels is almost 46 and that could rise by a further 3% even 11 panels exceed the inverters spec.
There is nothing realistic you can do with your new panels, adding them in parallel with part of the existing string achieves nothing as the current will be limited by the remaining panels in the string.

However I read here manual that your inverter supports two strings, so buy enough panels to make up another string given the minimum voltage requirement. Please check your actual inverter supports two strings first as the manual I found is for many model varients.
 

sagor

Joined Mar 10, 2019
439
Also, that inverter is rated 3300W. With 450V at full 9A, you are over 4000W, so adding more panels, even if you could, would overload the inverter. Not a good idea. Best to get a second inverter and more panels if you want to increase your output. With just the one 3300W (or 3000W output) inverter, you are limited by the inverter, not your solar array.
Inverter specs are maximum of "either or", not all combined. Your total capacity is the wattage, for example either 500V at 6A or 250V at 12A. You cannot run 500V at 12A
 

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Unfortunately as VOC of your panels is almost 46 and that could rise by a further 3% even 11 panels exceed the inverters spec.
There is nothing realistic you can do with your new panels, adding them in parallel with part of the existing string achieves nothing as the current will be limited by the remaining panels in the string.

However I read here manual that your inverter supports two strings, so buy enough panels to make up another string given the minimum voltage requirement. Please check your actual inverter supports two strings first as the manual I found is for many model varients.
Input says 180 to 450 something.

Can i do 6, 6 in series and both in parallel?

( 45 x6 ) + ( 45 x 6 )

Your second option, buy enough panel is way more costly than trying to save few units with these 2 new panels. Also not enough space on terrace :)..

6 plus 6?
 

Deleted member 440916

Joined Dec 31, 1969
0
Yup that works as two separate strings, dont be tempted to connect them in parralel as the inverter input current rating is just 16A.
 

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Hello Mr.
Also, that inverter is rated 3300W. With 450V at full 9A, you are over 4000W, so adding more panels, even if you could, would overload the inverter. Not a good idea. Best to get a second inverter and more panels if you want to increase your output. With just the one 3300W (or 3000W output) inverter, you are limited by the inverter, not your solar array.
Inverter specs are maximum of "either or", not all combined. Your total capacity is the wattage, for example either 500V at 6A or 250V at 12A. You cannot run 500V at 12A
Hello
Also, that inverter is rated 3300W. With 450V at full 9A, you are over 4000W, so adding more panels, even if you could, would overload the inverter. Not a good idea. Best to get a second inverter and more panels if you want to increase your output. With just the one 3300W (or 3000W output) inverter, you are limited by the inverter, not your solar array.
Inverter specs are maximum of "either or", not all combined. Your total capacity is the wattage, for example either 500V at 6A or 250V at 12A. You cannot run 500V at 12A


Please correct me.

3300w is output. What has it got to do with input? I measured on bright sunny day, voltage was 45, amp was 6. (Short circuit)

Which gives 45 x 6 x 12 = 3240 watts.
 

boostbuck

Joined Oct 5, 2017
42
3300w is output. What has it got to do with input? I measured on bright sunny day, voltage was 45, amp was 6. (Short circuit)
Which gives 45 x 6 x 12 = 3240 watts.
Output Power = Input Power - Inefficiency Losses.

The grid-tied wattage delivered will be slightly less than the solar panel wattage available. The wattage limit of the input is specified by the manufacturer, and determines the maximum amount of panel you can install.
 

BobTPH

Joined Jun 5, 2013
3,304
Hello Mr.

Hello




Please correct me.

3300w is output. What has it got to do with input? I measured on bright sunny day, voltage was 45, amp was 6. (Short circuit)

Which gives 45 x 6 x 12 = 3240 watts.
You are already supplying more power than your inverter can handle. Giving it still more will not help.

Bob
 

Deleted member 440916

Joined Dec 31, 1969
0
Actually having a higher installed solar panel rating than the inverter is perfectly normal as it allows a higher output in poor weather conditions that depending on where you live may make up a considerable portion of the year. Its perfectly ok providing you don't exceed either the voltage or current ratings of the inverter. The inverter won't be destroyed by being under-rated as it will only take as much power as it can cope with or has been designed for provided the above constraints hold.

Typically the reason for a source current limit (Isc) is to ensure the inverter protection circuits are valid against an internal fault and able to prevent fire, this is the danger of connecting strings in paralleled, source Isc is doubled.

Something I forgot to mention with two strings, ensure both are fitted with DC isolators or preferably a single 4 pole unit to avoid confusion.
 

Janis59

Joined Aug 21, 2017
1,332
Generally it should not be any difference series or parallel, but it is and rather large. Except the case when Youre using a mass product SMPS MPPT device made for 36 V input and there is nothing to do with it, the big player here is dark idle current. For good solar element it may stand 1 mA per m2, for bad probably 100 mA or even 1/2 A. There is practically no difference with result between both in the sunny day, but when a shady day, and my place is having shady days 360 days a year, then Solar Factor may fall from 380-560 W/m2 as at bright Sun at Tropics toward 60 W or 15 W or even 0,6 W/m2 as today. Then even small current is better than nothing therefore this loss value is crucial. And switching in series, the loss is the same as one battery do, whilst switching in parallel the loss will be N-fold larger. I contrast it is worth to mention that most of German solar roofs are mounted parallel to 36V. Reason is that mentioned 100 Amp controller costs only 5 USD.
 

Janis59

Joined Aug 21, 2017
1,332
Please correct me.(..) I measured on bright sunny day, voltage was 45, amp was 6. (Short circuit)
I measured today, 20x60 cm large solar cell freshly from shop under open sky ar 12:00 day short circuit gives 0,02 microamperes and open circuit gives 13 milivolts. Panel is checked, under table lamp 1 meter afar it gives 13 Volts and 1/2 ampere.
 

andrewmm

Joined Feb 25, 2011
1,456
Panels in parallel only work if the illumination and efficiency of both bank is identical,
If one bank gives out more volts than the other then the bank that has the lower voltage turns into a current sink,

QED, you can not parallel,
 

Audioguru again

Joined Oct 21, 2019
3,171
Isn't the solar power much less in the morning and afternoon than at noon? Does noon last for 10 minutes?
How often to you wash grime off the solar panels? Recently my city sprays brine on snowy roads and everything gets covered with it.
Do you live on the equator of earth so that the sun is never "low in the sky in winter"?
 

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Hello Mr.

Hello




Please correct me.

3300w is output. What has it got to do with input? I measured on bright sunny day, voltage was 45, amp was 6. (Short circuit)

Which gives 45 x 6 x 12 = 3240 watts.

3300 watts you referring to is output.

Input can be anything right?

That's dependent on input specs right?

Sorry.

Well after googling i found this. Attache
Hello Mr.

Hello




Please correct me.

3300w is output. What has it got to do with input? I measured on bright sunny day, voltage was 45, amp was 6. (Short circuit)

Which gives 45 x 6 x 12 = 3240 watts.

Ok, you mean inverter itself cannot give more than 3300 watts no matter input.

What i am saying is, That is fine.

80% of times my panels don't give more than 5 amps.

If they exceed, should we not be under -- input range as per specs?

Doing 6 x45 plus 6 x45?

9 amp is written on pannel. Assume its 6. Now is there anything i can do with 2 panels?
Isn't the solar power much less in the morning and afternoon than at noon? Does noon last for 10 minutes?
How often to you wash grime off the solar panels? Recently my city sprays brine on snowy roads and everything gets covered with it.
Do you live on the equator of earth so that the sun is never "low in the sky in winter"?
Maximum rating is 9 amp.(sticker)

I measured, full washed full sunlight to ne 6.8 amp.

But as experts here said, not taking any chance, or i will fry my inverter.

Will only do if it's sure going to work. Can't experiment, all this is costly.

Yes equator, India.
 

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Actually having a higher installed solar panel rating than the inverter is perfectly normal as it allows a higher output in poor weather conditions that depending on where you live may make up a considerable portion of the year. Its perfectly ok providing you don't exceed either the voltage or current ratings of the inverter. The inverter won't be destroyed by being under-rated as it will only take as much power as it can cope with or has been designed for provided the above constraints hold.

Typically the reason for a source current limit (Isc) is to ensure the inverter protection circuits are valid against an internal fault and able to prevent fire, this is the danger of connecting strings in paralleled, source Isc is doubled.

Something I forgot to mention with two strings, ensure both are fitted with DC isolators or preferably a single 4 pole unit to avoid confusion.
Thank you.

Can you explain last part again? My inverter jas only 1 string. Ie. Only 2 cables can go in plus and minus.

Someone said (45x6) + (45x6)
2 Parallel will cross ampere limit.. total Watts

Well, i thought in parallel means amp will remain same..below 9..

What i am thinking:

Close your eyes and imagine 9 panels (10 are presently working fine)

9 + (3x45) Parallel..
Inverter will only see 10 panels but as if in full sunlight
 

Deleted member 440916

Joined Dec 31, 1969
0
According to the manual I found on the web your inverter supports two strings, please check the model number and manual carefully. If it only supports one string then you cannot use a 2 x 6 panel arrangement as that would exceed the inverters rated current...sorry

2nd part of your question already answered, current is limited by lowest current panel/s in string so adding panels in parallel with part of the string does nothing, again sorry.
 

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Panels in parallel only work if the illumination and efficiency of both bank is identical,
If one bank gives out more volts than the other then the bank that has the lower voltage turns into a current sink,

QED, you can not parallel,
You mean if off 10 panels, 1 panel is dirty with low amp all will be low?

Or 1 is extra clean all will be high..

How about 9 + (3x45) parallel..

Inverter will see 10 x 45 volts..

I am extremely sorry if i am being annoying. Have invested 1500 USD..

Thank you.
 

Thread Starter

moonbreakker

Joined Jan 15, 2017
21
Panels in parallel only work if the illumination and efficiency of both bank is identical,
If one bank gives out more volts than the other then the bank that has the lower voltage turns into a current sink,

QED, you can not parallel,

This may be useful?

Be it morning evening noon.

Volt remains 45.

Amp increases with sunlight.. (i measured)
 
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