7X Pro sapphire solar - not quite "solar"

Hi to all, 

Does anyone's solar charging work? I mean in new watch, without warrenty actions. I bought the watch 2 months ago. Today is beautiful sunny day. Battery level: 52%. Putted watch on the windowsill - nothing, exept it was hot. How quickly will the battery increase its charge by even 1% on such a sunny day? Maybe I put out too short, maybe 1h is too short?!
I restored the watch to factory settings, another attempt and nothing.
I sincerely regret this purchase. Not with "solar" in the name.

Thank you Guys for any suggestion.
Have a nice day!
Cris