(2) 12V Solar Panels....Series or Parallel?

PWM?

Isn't the 12/24v the output rather than input? Isn't that why you connect the battery first, so that it knows what the system voltage is ? I don't think that has anything to do w/ the series or parallel panels.
The type of controller however does.

Rbertalotto wrote:
I have (2) 140w 12V panels. The Bogart Engineering solar controller can operate on 12V or 24V input. Is there any advantage or disadvantage to wiring the panels in series for 24V rather than parallel for 12V?

If you series the panels for 24v with the PWM controller, the batts need to be wired for 24v too. Then you have to get 12v for running the rig.

It is a PWM controller

The instructions say:
"Up to 30amp maximum solar current. Four 135w solar panels for 12v system or 8 at 24v can be accommodated"

As I read and learn more, it appears the input AND output need to be either 12V or 24V........

So, if 24V, how do you utilize this in our 12V systems? Some type of "Step Down" transformer from the 24V battery bank? Or is 24V only used when a 24V inverter is deployed?

I find this all very interesting and your knowledge superb!

"Up to 30amp maximum solar current. Four 135w solar panels for 12v system or 8 at 24v can be accommodated"

A typical 130w panel has an Isc of 8.2a, which you will get in full sun. So a 135 will do 8.5a. Four of those makes 34a.

Then the usual advice is to have the controller able to handle 1.25 the total Isc of the array unless it has amps clipping at its max rating (that controller might have it--most PWMs don't), so normally four 135s would need a 42.5a controller (so you buy the next size up from that)

I'm not too concerned about the amp rating as I can barely fit the two 140w panels on my roof without shadowing. It is only a 20' Toy Hauler.

Looks like I'm going to run the panels in parallel and at 12V total.

Thanks

Use them in parallel. If you are going over 500 watts of panels we can talk 24v.

Forget the 24 volts, as that is the system voltage. Yours is a 12 volt system.

As far as the input voltage from the panels, it will be somewhat more than 12 volts even if you stay in parallel. (look at v specs on back of panels) Its the controllers job to limit those volts to what your batteries need (very debatable) If you connect the panels in series, you would very like over do the volt specs on the controller. You would need a MPPT type controller that is designed for higher volts.
But, if shading will be common for you, I would for sure stay w/ low voltage PWM anyway.

Rbertalotto wrote:

As I read and learn more, it appears the input AND output need to be either 12V or 24V........

So, if 24V, how do you utilize this in our 12V systems?

1) Yes. That's the problem with any PWM - voltage in and voltage out is the same, minus tapering.

2) You can't. This can be done with MPPT controller. Forget about series with PWM.

keep them parallel , its the only way that is sensible with PWM controller
if you go series the amps will be cut in half, voltage to the controller will double, and the controller will knock it down to 14 for charging
you will loose power IF you go series