This panel frieze excellence for its price: it continues to charge my battery to 18.00 at the end of January 2015, despite gray skies (black is there to here now 6:20 p.m.). Measured at 28V across the board at 16:30, always under gray skies in late January. Combined with a small 12V regulator "Solar Panel Charger 10A 12V / 24V controller dispatcher" 5 euros (ref STK-902059 / ASIN B007VLMRP2) and a 12V 7Ah battery, it is quite enough to give me light in my cabin garden thanks to LED bulbs 4W.