Adding another solar panel

[motion30]

I.have 3 275watt panels installed. I wish to add a 4th. Does it matter if I use a panel from another manufacturer as long as the specifications are similar?

[newhaul]

No as long as the voltages are same

[Viking Sailor]

If you are using a MTTP controller the Vmp needs to be the same.

[Viking Sailor]

Correction:

If you are using a MPPT controller the Vmp needs to be the same.

[john61ct]

I believe controllers like the Victron give more flexibility than others?

panels in series, match Amps (I think Imp)

in parallel (incl series strings in parallel) match Volts (Vmp?)

on both "pretty close" is OK

[motion30]

I am going to run four panels in two strings so both in series and parallel. I have an Outback mppt controller does the new panel need to be exactly the same voltage as the old ones or can it be within a couple of volts?

[fallingeggs]

I had a similar issue not long ago. Where I landed was that if the Vmp isn't within a few percentage of each other, then there will be measurable efficiency loss. Thinking in the range of low tenths of a volt. Otherwise, the MPPT will try to hit the average Vmp, which won't be optimal for any panel. If you're average Vmp drops by 5% (about a 1 volt drop), then you, more or less, lose 5% of the panel's rated output.

For whatever reason, my original panels have a rather odd Vmp, which I couldn't come close to matching. I sold my big solar controller and replaced it with two smaller ones, with no outlay of additional cash. If I had to spend $100+ on a new controller, I might have went down a different path. Maybe.

[a64pilot]

Originally Posted by newhaul

No as long as the voltages are same

This has me thinking, I have four 250W panels in Parallel, when one is shaded it often falls to 24 VDC or so while the other three are 35 VDC.
Is the low volt one just not contributing anything in that instance? Cause when its cloudy the output for the whole array will fall to 24 VDC of so, yet it still charges the bank at 20 amps or so.

[thinwater]

In theory, a perfect match is best. How else can the controller optimize the conversion?

However, with shading, and differences in wire length, temperature, sun angle, and aging, unless each panel has a dedicated controller, there will be always be some mismatch.

The truth is that you should be able to find something very close.

[motion30]

Ok so I've been searching online and cannot find a panel with similar voltages. Here's what I'm looking for if anybody knows of a brand that matches
275 watts. Mpv 35.82 mpc 7.86 ocv 46.98. Short circuit current 8.18

[motion30]

The company that made my solar panels in Spain as went out of business. Anybody that can just a 275 watt panel with similar voltage as I posted it would be greatly appreciated