How many panels per combination

sabo

New Member
I am trying to determine how many panels I can (should) put in series. Parallel or Series-Parallel configuration. I am looking to do a 48 V system no batteries. I am planning 16-20 panels to start.
I live in Southern California, a few days in the summer it is 110 degrees and in the winter some nights rarely get into the high 20s at night. But high 20s is very rare. It is sunny from sun-up to sunset almost all the time except for when it rains which sadly these days seems rare.
My confusion is these show 37.6 Open circuit voltage (VOC). 37.6 V x 4 = 150.4
the inverter shows
  • high PV input 250V (Voc)
in the specs (link below) Should I do more or less than 4 panels per section?
Are eco-worthy combiner boxes any good
Any other input is appreciated.


I am looking to buy these panels

Specifications:

Rated Power: 250W
Open circuit voltage (VOC): 37.6 V
Max power voltage (VMP): 30.3 V
Short circuit current (ISC): 8.85 A
Max power current: 8.27 A
Power Tolerance 0/+3%
Maximum system voltage: 600V (UL)

To use with this Inverter

  • high PV input 250V (Voc)

LV6548 Solar inverter 6500w 110v 48v MPPT 120A PV input 250vdc WiFi batteryless

I am trying to determine how many panels I can put in series. Parallel or Series-Parallel configuration
 
Last edited:

OffGridInTheCity

Solar Addict
You don't want the VOC to exceed the specs of the charge controller. So you could - in theory - do 6 panels in series. 6 * 37.6v = 225.6v which is < 250v. But under certain conditions (such as very cold) its possible this will vary upward a bit (hyper-voc) so if that applies to you maybe 5 in series would ensure you never go above 250v. At the minimum side - typically you want to be higher than the max battery voltage - so 2 * 30.3v = 60.6v would just be a bit higher than typical 48v 18650 lithium-ion max of 58.8v.

Personally - I'd think in terms of 3 or 4 or 5 in series. Some considerations to choose between 3/4/5 might be the panel count (so it comes out even), physical wiring / combiner box easier or harder, the more in series if 1 panel fails then the whole series fails along with it, maybe stick with 3s to accommodate <250v equipment in the future, if you have really long wire runs (hundreds of feet) then higher voltage might lead to less wire resistance... all lessor variables for your specific situation.

I don't think 3 or 4 or 5 in series would be wrong - just slight pros/cons.
 

MichaelK

Photon Sorcerer
I'm also in Southern California, and my area experiences winter frosts every single year. I popped your numbers into Midnight's string calculator and found the Voc for 28 degrees F.
So, for your winter low, expect to see a Voc of 164V for four panels in series. If your unit has a V limit of 250V, then no problem. Six in series I think though would be dangerously close to the limit and just tempting fate.
1627235765104.png

Five in series looks like it would be the best choice.
1627236073087.png
 
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