Would you go series or parallel (solar)

[cdrobbins77]

Here’s what I have:
2 Renogy 270 watt 24 volt panels and a Renogy Rover 40amp MPPT charge controller
Battery bank is 4 6volt AGM batteries that will be wired series/parallel to make a 12v battery bank. In the future I may add more panels to the system, but for now would you wire the 2 panels in series or parallel? And why? I mostly understand the pros and cons of each, but with only 2 panels it seems like I could do either and get about the same result.

[CHEESE_WAGON]

One potential issue with wiring series is that if one panel is shaded, it may affect the other's operation. This is why it's important to know if the individual cells on your panels are wired in series or parallel. If part of a panel with series-wired cells is shaded, it may not work at all. Those with parallel cells don't suffer this problem. I can imagine that wiring two panels in series might have the same effect.

Though I do know that in typical electrical circuits, wiring series increases voltage, wiring parallel increases amperage. Not sure if either applies in this situation though.

[bus-bro]

If I had your panels I would probably wire them parallel. You have an amp (and volt) input limit on your controller and that could come into the picture if you add more panels. Though, that depends on your storage bank voltage. There are optimal voltages to when pushing the charge through the controller then into the batteries.

Pick your battery bank first, at least as far as voltage. My bank is 4 (up to 6) golf cart batteries at 12 volts, charged by 80 volts into the controller. Not the most efficient curve on the controller because of that 12 volt battery. If I did it over I go with a 48 volt battery bank


I have (2) 400 watt series strings of nominal 12v panels feeding into separate MPPT 30 amp controllers. All I got to do is bolt the stuff up.

[Danjo]

Those panels have a short circuit amperage of 9 amps, so in parallel you have 18 amps at an open circuit voltage of 38.6 volts. This is well within the limits of your charge controller.

I’d wire in parallel since it’s within the operating parameters of your controller and you wouldn’t need to worry about output drop from shading

[cdrobbins77]

Originally Posted by Danjo

Those panels have a short circuit amperage of 9 amps, so in parallel you have 18 amps at an open circuit voltage of 38.6 volts. This is well within the limits of your charge controller.

I’d wire in parallel since it’s within the operating parameters of your controller and you wouldn’t need to worry about output drop from shading

Thanks. I think that’s the route I’ll take

[dzl_]

Originally Posted by cdrobbins77

Here’s what I have:
2 Renogy 270 watt 24 volt panels and a Renogy Rover 40amp MPPT charge controller
Battery bank is 4 6volt AGM batteries that will be wired series/parallel to make a 12v battery bank. In the future I may add more panels to the system, but for now would you wire the 2 panels in series or parallel? And why? I mostly understand the pros and cons of each, but with only 2 panels it seems like I could do either and get about the same result.

The first thing you want to check is whether your charge controller can safely handle either configuration in the coldest conditions you will be in. The datasheet or stickers on your panel will state Isc and Voc,

• You will want to make sure that Voc x 2 x temp correction is below your chargers max input voltage if you connect in series
• You will want to make sure that Isc x 2 is below your chargers max input current if you connect in parallel

As for pros and cons:

• Connecting in series is more efficient. Connecting 2 panels in series will be 2x the voltage, 1/2 the amperage, and 1/4 the voltage drop compared to 2 panels connected in parallel. This should be the default configuration unless you have a good reason not to.
• I can think of two good reasons to connect in parallel. The first is simple, if your charge controller can't handle the voltage but can handle the amperage, connect in parallel. The second is partial shade, shade can be devastating to series connected panels. The current (amps) of all panels in series is pulled down to that of the shaded panel. If you connect in parallel only the shaded panel will have its output reduced.