I had a vv Ego battery delivered the other day which on first charge took 3 mins for the USB charger dot to change from red to green and sure enough the battery was only lasting a few minutes. The second thing that was different to my other batteries was that the light surrounding the firing button would remain lit during charging. A dud battery to be returned to the vendor I thought. Inadvertently however I left the battery in the charger. To my surprise, the battery was fully charged.
I'll need a charger of a different type to determine whether the battery or the charger is at fault, but one thing is sure, you can't always trust the indicators to inform you.