Adding additional panels

rdg1

Hello all.
I am looking to increase the number of solar panels I currently have and would like to read your thoughts and opinions.

Current setup;
6- REC320NP, two strings, three panels each.
Outback FlexPower One 3648
200AH AGM battery bank

Cannot find additional 320W 60 cell panels, (reasonably priced), but have found 240W 60 cell panels.

I would like to keep each "string" approx the same, or does it matter?

I figure that 4 of the 240s would equate to 3 of the 320s.

Thoughts?

thanks for your input

BB.

For paralleling solar strings, the Vmp-array for each string should be ideally within 10% or better of each other (i.e., 90V Vmp-strings, the additional strings" should be around +-9 volts of 90 Volts (or less) for optimum MPPT controller function.

So, in this case, if you have 3x 320 watt @ 60 cell panels strings, then "match" with 3x 240 Watt @ 60 cell (roughly Vmp~30 volts typically) strings... That will be "perfect" (you may need to check the series protection fuse/breaker ratings... The 240 Watt panels may need a lower Ampere rated over current protection device.

Placing 4x 240 Watt panels in series will not work well/correctly for MPPT controller.

For series strings, again suggest +/- 10% of Imp of the other panels in the string... Don't know the Imp rating of your panels--But probably not a good candidate for mix/match in the same string with existing panels.

-Bill

rdg1

Bill, thanks for the info, I will look at it more in detail later today.
Will probably be asking more questions once I do a bit more research.
Rob

BB.

You are very welcome Rob.

-Bill

Surfpath

I agree with Bill that it’s going to be a three panel series addition. You are right, 320 Watt 60 cell panels are a little hard to find. As long as the IMP‘s match up fairly closely (10%) you’re good to go.

rdg1

Thanks Surfpath, (and again Bill),  decided to just redouble my efforts and I did fine some REC TwinPeak 3 325 that I should work well.  I looked for reviews of this panel but could not find anything other than specs.

After this addition, I believe my solar output will be pretty good, (just shy of 2900W).  Next is to upgrade my battery bank from the 200ah AGM to 300ah lithium.