General question about a handheld fan / 18650

Fan comes with a 18650 rechargeable which I have plenty of. My Fenix 4 bay charger charges up to 4.2 volts so no need to use the USB charging cable that comes with it I can just pop the battery in the charger... I think hence the question

The fan says the following:
Input voltage 5 V
Output voltage 5-9 V
Battery 18650 3.7 V

So if I have a 3.7 V 18650 which can charge to a maximum of 4.2 V (never understood why they don't call it a 4.2 V battery instead of a 3.7) then that means the maximum voltage output of the battery is 4.2.

So how can that operate a fan that has an output voltage of 5 to 9 V? Is the 18650 capable of being charged to higher voltages with a USB cable??

I'm just totally confused by all of this can anyone enlighten me

Really?? None of the gurus have an answer? Hard to believe that this has stumped even the experts themselves, so at least I don't feel bad not knowing

It uses a boost driver that boost th voltge to what the fan need
It's like a single 18650 xhp35 light. The xhp35 led needs 12v so it uses a boost driver

How dose the boost driver work? I think it use tesla coil. I don't know any other way of boosting voltage

Search Wikipedia for "DC to DC converter." There are many ways to take one voltage and step it up or down. Flashlight folks usually say "buck" or "boost."

Thanks guys I knew someone here would know! And believe it or not I had no idea that kind of stuff exsisted in cheap knock off electronics. Thought that converter's and such was only for more expensive electronics!

They call it 3.6V or 3.7V because that's about the voltage where the battery spends most of the voltage during the discharge cycle. It's often referred to as nominal voltage. A 12V lead acid battery is the same, it can often be 13V for example, and a 1.2V NiMH cell might be charged to 1.5V.

Also, I'm not entirely sure what the output voltage is all about. Is there an output on the fan? Or is it variable speed, and the 5-9V range could be related to that?

Theoretically it could be that the input voltage is shifted down, rather than the battery being shifted up, but that'd be unusually low for a fan.