If the vita charges at least your battery is fine. Must be the charging cable.
I used another cable. 2 bad cables then?
P.S. wtf your name counts as censor bypass.
How does the nyko power grip charge? Through the slot? I have not used it if it does charge through the slot it mean that both the slot and the battery are fine and the problem must be in cable (or the adapter). Could be the adapter since you have already used two cables.