How many panels can I wire in series for 48V system

[forest_face]

I have 8 195 watt 12 V solar panels.

I have a 48V DC to 120V AV 5000W inverter. I'm a bit confused about how many panels I can wire in series. I'm assuming that I can wire four 12V panels in series (to get 48V), but I wonder what happens if I exceed 48V.

The documentation for the inverter has a max open input voltage of 500V and a MPPT input range of 120V to 450V DC. I'm not exactly sure what these mean, but can I (for example) wire all 8 panels in series and go into the inverter? Or should I write 2 series banks of 4 in parallel into it?

Any help would be appreciated.

 

[yodamota]

In order for your inverter to work at all the voltage of the VMP needs to be withing the 120v-450vDC. It wont charge under 120vDC. Not sure if 8 12v panels will work.

8 x 17VDC = 136VDC. so just barely....

 

[forest_face]

In order for your inverter to work at all the voltage of the VMP needs to be withing the 120v-450vDC. It wont charge under 120vDC. Not sure if 8 12v panels will work.

8 x 17VDC = 136VDC. so just barely....

Thank you for your reply.

So I would need to get *at least* two more panels, or enough panels, wire them all in series so they they add up to between 120v and 450v? Is this correct?

 

[Mattb4]

You want to look at the actual Voc and Vmp for the panels instead of just saying they are 12v panels. Likely they are 22Voc and 18Vmp. 22 x 8=176Voc so should be quite adequate to start and the Vmp of 144vDC should give you a decent margin above the minimum for running. you possibly could get away with 7 in series but it would be close to dropping below minimum voltage whenever it was low PV levels.

 

[forest_face]

You want to look at the actual Voc and Vmp for the panels instead of just saying they are 12v panels. Likely they are 22Voc and 18Vmp. 22 x 8=176Voc so should be quite adequate to start and the Vmp of 144vDC should give you a decent margin above the minimum for running. you possibly could get away with 7 in series but it would be close to dropping below minimum voltage whenever it was low PV levels.

The documentation says VoC 23.7V and Vmp 19.8V.

 

[yodamota]

so yes the 19.8 x 8 = 158.4VDC at 25*C.
The VMP will drop when its hot out. so on really hot days it might drop lower than the 120v minimum.

Try punching the info on the panels into this tool. https://www.midnitesolar.com/sizingTool/index.php
It will tell you the figures at the hottest day and the coldest days.

Since the VOC doesn't have any current. I believe using the VMP will give you a more accurate representation of the operating voltage of the array.

 

[Bop]

With that combination, your only choice is all in series, or run an external charge controller that has a better MPPT range, or buy more panels...
It is 'barely' into the MPPT range, and will struggle in poor generating conditions (and will generate less total kwh per day than a series array with a higher voltage...)
Plus you only have 1.5kw of panels, depending on your exact location in the US, that would likely be only 7-8kwh a day in total generation at best- not exactly a lot (get that inverter to full power and in just over an hour you will have used an entire days generation!!)

 

[time2roll]

12v panels? I would skip up to large 24v panels for that inverter. Still need about 10 in series.

 

[Bop]

12v panels? I would skip up to large 24v panels for that inverter. Still need about 10 in series.

Depends on the panels involved (not a fan of this '12v'/'24v' nonsense, as it is the Voc that matters) and with panels in a variety of Vocs ranging from about 20V up to over 80v in a variety of voltages- there really isn't any distinct '12v steps'
Something like the Sunpower Maxeon 3 range have a 81.5v Voc- ten of those in series would be a spectacularly bad choice for a MPPT controller with a PVmax rating of only 500v being fed over 800v!!!!

(spectacular would be an understatement...)

 

[time2roll]

Yes a 112 cell panel would not be considered 24v nominal.

My comment was based on 12v panels are generally a bit higher in price per watt.

 

[Bop]

But with so many different Voc and Vmp ratings- there really isnt any distinct point that you can say that 'this is a X volt panel'

Plus the Maxeons...

and the wattage is no guide to the Voc rating...
A 555W with a lower Voc than the 410w!!!


The 555W (50.34v) is lower than the 410w (81.5v)- and very similar to the 190w (45.2v), which is double the 200w (22.32v)- and my own 250w ones (the Munsterlands bottom left in the top pic) are different to all the rest with a 38v Voc...

 

[time2roll]

Of course you can. And that Maxion 3 is not one of them.

Usually 60 to 72 cells would be considered 24v and are generally lower cost than "12v" panels.

 

[Bop]

Well it isn't considered that way by installers in Australia- it hasn't been a 'thing' since the 80's or early 90's...
Maybe you guys will catch up in 2050-2060 lol