Solar upgrade, mixing panels?

[Ronnie RIMOR]

I would like to add to my existing one panel system, question does the new additional panel need to be the same size, type and output? and how would I wire it Parallel or series?
I think the existing is circa 100W I have upgraded to a 20A MPPT controller.
Thanks in advance

 

[Richard n Ann]

Wire it in parallel is the consensus on here. And the working voltage has to be the same or the higher voltage panel will be the only one that works.

The knowledge bot will be along soon

 

[autorouter]

The knowledge bot will be along soon

While we're waiting, here's a bit more info. I'd guess your 100W panel is the '12V' type, ie suitable for 12V batteries, not 24V. Its voltage will be from 18 to 26V. If you get a similar panel its voltage will be about the same. I know that sounds obvious but for example a 250W panel will likely have a voltage of 30 to 40V.

Technically you want to match the 'Maximum Power Voltage', Vmp. The other voltage, the Open Circuit Voltage, Voc, will probably match if the Vmp's match, but it's less important. However it can be difficult to find the specs of a fitted panel, even if you tape your phone to a stick and poke it under the panel to read the label. Look at the arrangement of the cells on the panel (for example 9 x 4) and get one with the same layout.

 

[Guigsy]

You can run in series or parallel. There are advantages and disadvantages in both situations. Depending on how badly mismatched they are, you might only ever get 80% of the theoretical output from them. Stupid things like the shadow from your aerial will kill the output from one panel (even if it's only covering a tiny bit) and that will drag down the output of the other panel.

To get the maximum out of them both, you're best off with a second MPPT charge controller. But that obviously costs a lot more.

 

[Ronnie RIMOR]

Thanks for the info. Prices of panels seem to be reasonable it sounds like getting two new to replace the unknown one might be money well spent.

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[Raul]

The old panel will drag the new one if both on the same mppt. Even if you chose the same 36cell panel, the parameters will differ. Newer panel will work on a different power point, and the mppt will have a hard time work looking best power point. It will work, but with loses. Best to go for two brand new 100w matching panels, or even better, a single 60cell panel. There are plenty used good 60cell panels. The other day I came across Trina 285w for 60 quid, on eBay, manufactured 2019.