When solar panels don't work

I thought I would add another word about keyboard trends. A coworker has bought the Logitech K750, the one with solar panels to recharge the battery. This keyboard has excellent reviews on many websites, or even on Amazon. I somehow always found the idea a bit strange, it looked like the old solar panel calculators that used to be trendy when I was in primary school.

Well after maybe 6 months of use, he needs to change the battery! It sounds like the solar panels were just a marketing plot after all.