I ordered some days ago a new ZachTek WSPR desktop transmitter for some field tests. This transmitter is powered by 5VDC via a simple USB cable.
As an avid reader of Tom's K4SWL Blog I've seen HAMs using many times a small powerbank from Talentcell - the YB1203000-USB - which is advertised as a 12V 3.000mAh powerbank.
As can be seen on their website, that the powerbank uses three 18650 LiIon cells. The regular voltage of an LiIon battery is 3.6V - three cells will give 10.8V and not 12V?!
Initally with not further searching on the internet, I ordered the powerbank on eBay, as the specs looked fine on first glance :-/