The other day my bicycle light gave out, so I took it apart - was not the most expensive option, but also not the cheapest.

It was advertised as having a 2600mAh battery, but when I opened it up, inside there was a 1700mAh cell. Also no sign of purported weatherproofing, as the lens was not even glued in.

I have a 2000mAh cell in the same form factor (approximately 500Wh/l, so believable) on its way from China, which makes me wonder how did they come up with that 2600mAh figure.