Parallel Vs Series

[A S R]

Ok, stupid question #3!
If I want to join 2/3/4 255w panels together which is the best way to do it? These are at a house and NOT on my motorhome.
I have 1 panel up already and on a cloudy day it’s giving me this.

At the moment I have just 1 12v battery on charge.
What controller would I need to have 4 panels connected?
How would I wire them together?

 

[RogerIvy]

Are the panels identical?
If not do you know the specs of all the panels?
In particular we need to VOC (closed circuit voltage) of all the panels. The max amps would help too.
I'm referring to the labels on the panels, not what the MPPT is reporting.

 

[autorouter]

4 x 255W panels will potentially push out 1020W. A controller charging a 12V battery would be outputting 72A at 14V. So you'd need at least a 70A controller for charging 12V batteries. If charging 24V or 48V batteries the amps would reduce to 36A or 18A, so a lower amperage controller could be used. But that depends on whatever you are using the batteries for. If you are buying a new inverter, consider going to 24V or 48V, it's less amps and easier/cheaper for the wiring etc.

For the panels, look at the voltage limit on the controller panel input. Victron make it easy, the MPPT 75/15 has an input limit of 75V. That's enough to handle two of those panels in series. The bigger controllers with 70A or more output can usually take at least 150V, so you could put four panels in series if you want. Or wire two panels as a series string, then another string of two in parallel.

If panels are connected in series, the voltages add together. Each panel is 30V or more, so even a couple of panels in series can produce a dangerous voltage.
Note carefully, once you start getting voltages over about 50V you definitely need to start taking precautions against electric shock. Especially if you are working on a roof or up a ladder.*

 

[Ditcha]

Just to add when panels are wired in series you can use lighter gauge cable as the voltage adds up and the amps stay the same, we're as in parallel the amps add up and voltage stays the same higher amps thicker cables.