Originally Posted by Paxman
It´s most definitely wired in series. It´s clearly made for AA batteries and since USB is 5 V you need to connect the batteries in series: 1.5V X 4=5V.
The capacity is depending of the AA´s, if they are say 1500 mAh each the pack will also have 1500 mAh.
If you want 4 X 1500 mAh (5000 mAh) you connect the batteries in parallel but then you would only have 1.5V.
It's clearly made for AA batteries when it doesn't state such ANYWHERE in the link? Are you sure you are looking at the same ebay auction that was linked? It even states in the TITLE that it is for 18650 batteries.