Need Help - Solar Charging Question

[Huck]

I'm trying to do what I have read others here have done.

I have a 100 watt solar panel (RENOGY 100W Watts 100 Watt Polycrystalline Solar Panel) connected to a charge controller (Renogy 30 Amp PWM Charge Controller Regulator Off Grid for Battery Charging).

The output from the charge controller is connected to aux power and ground on a 7-way blade rv connector (vehicle side).

Before I plug it in to the trailer connector, I want to make sure the voltage level is right. I'm reading 21.5 volts. Does this seem right?

[Gina D.]

It could be right if measuring directly from the panels. If you are measuring the output of the charge controller, it should be in the 12 to 14.5 volt range, given your panels are in full sun. (Depends on the controller you have)

[Jon Vermilye]

While that sounds like the normal voltage from the panel, it is high for the output of the controller. I'm not familiar with their controller - it may be that it does not provide the proper voltage unless connected to a battery. Depending on the state of the battery, the output should be in the range of 13.2 - 15 volts when connected.

[Huck]

I'm definitely going through the controller.

[Jon Vermilye]

If it was me, I'd try connecting it to a stand alone battery first to see if it drops to the proper voltage. I'll bet it does, but I wouldn't want to risk the trailer's electronics finding out...

[Huck]

Thanks everyone. I just got this response from Renogy. I asked them the same question I posted here.

Yes, that is the open voltage (when there is no load connected). When you connect a solar system, you want to connect the battery first to the charge controller and then the solar panel.

I have another related question, but will start another thread.