24v solar panels

[clev]

I just checked and my panel Optimum Voltage is 17.9 volts and the Optimum Amperage is 8.38 amps = 150 watts. So, 3 of these panels are 450 watts, no matter how they are wired. In series, (17.9v x 3) x 8.38a = 450 watts; or in parallel, 17.9 x (8.38a x 3) = 450 watts. Here are the specs on my Renogy 60 amp MPPT controller:

Nominal System Voltage: 12v/24v/36v/48v/ Auto Recognition.

Max. Solar Input Power: 800W (12V), 1600W (24V), 2400W (36V), 3200W (48V)

Rated Battery Current: 60A

So, it appears that all of my questions and concerns have been answered. Thank you again, Chad; everything is quite clear at this point. Now, if I can talk my wife into mounting 2 new panels and rewiring everything in series.....

[thor293]

I have not read through all the comments so if this has been covered ignore me. If you have an MPPT controller you can series panels up to the rated volts, my Renogy is limited to 100 volts. Since you have so many panels you could spilt them in half and then parallel them together. So say you have 8 panels you can wire 2 sets of 4 in series giving you 48+ volts, then parallel the 2 sets together. This will drop your voltage but your amps being put out by the controller will be the same or possibly better. I spoke with one of the Renogy techs about this. Main key is dont run voltage over the rated controller. They have one controller I think that is rated to take up to 150 volts.
PS: If you are going to parallel panels you have to have equal number of panels in each set.

[clev]

Thor, one of the mistakes that I was making was assuming that my panels were 12 volts; they are not, and the calculations were confusing the heck out me. After being prompted by Chad, I checked my panels, and they are 17.9 volts/8.38 amps. And, again being prompted by Chad, I checked the spec sheet on my MPPT controller and learned the max wattage for each configuration. Armed with that information, Chad's reply should clear things up for you. If not, post again with those numbers.

[thor293]

Originally Posted by clev

Thor, one of the mistakes that I was making was assuming that my panels were 12 volts; they are not, and the calculations were confusing the heck out me. After being prompted by Chad, I checked my panels, and they are 17.9 volts/8.38 amps. And, again being prompted by Chad, I checked the spec sheet on my MPPT controller and learned the max wattage for each configuration. Armed with that information, Chad's reply should clear things up for you. If not, post again with those numbers.

Gotta ya!~

[heiser252]

Glad I could help.

If you run 3 strings of 2 panels in series (the way I would go to minimize potential shading issues), you would have a voltage of 35.8 (17.9+17.9) and an amperage of 25.14 (8.38+8.38+8.38). This would in essence give you 900 watts at 36 volts, which is well within you controller’s capacities. Of course these would be maximum numbers at peak conditions that you probably will never actually achieve in the real world, but it is what you need to base your calculations on.

When you run panels in series, I like to minimize the number of panels in the series to minimize potential shading issues. The way solar panels work, if you shade any part of the panel you can greatly reduce the panel’s output. When you run panels in series, you in essence turn the series string into one big panel. Now if you shade any part of any of the panels in the series, you will reduce the output of the entire series set. With this in mind, I prefer more parallel strings of small series sets. So for your six panels, I would do three strings of two panels.

[clev]

Thanks again, Chad. This has been very informative for me. For those that may be following this thread for information, Chad’s last post was a reply to a PM that I sent to him. While planning the addition of 2 panels to be added to my 4 panel system, wired in series to produce two strings of three, I noticed that the configuration (17.9v x 3) would exceed max voltage on my controller. I asked him for advice.