Thanks for your suggestions. FYI - The panel surface is clean. IIRC, the batteries were at about 90%, based on my Balmar SOC display; a 12.7 volt reading There is a controller - it's a Renogy 20 PWM.
I'll check the incoming voltage at the controller. Not sure how to check voltage "right at the panel". I thought the panel could be damaged if unplugged from the controller, while in sunlight. I'll get re-acquainted with the controller manual, too. Thanks, Pete W. Siren Song '91 C&C 30-2 Deltaville, VA.
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