Generally speaking, the merest of shadow on the panel will mean the loss of most of the panel power.

Checking the OCV and CCV, in good sunlight, should indicate the panel is OK.  The specs will be on the back of the panel.

On 19 August 2025 at 18:20 duncan webster 1 Said:

CCV? If the output is shorted there is no voltage?

CCV under load I suspect was the intention of the comment.
i.e. Close/Complete the Circuit to a partially discharged battery and measure the Voltage accross the battery open circuit and again whilst charging.
I’m assuming it’s a 12v battery, so nominally charging at something like 14v; 200W suggests a max charge current of about 14A in full sunlight, but I can’t imagine it would give that on a cloudy day.
You could always put a 10A ammeter in series, twixt battery and panel, after partially covering the panel with a sheet of cardboard, then gradually slide it off whilst observing the charge current variation.

Bill