Some Quick Power Calculations
Battery, per the specifications is 9800mAh (36Wh)
Modern (internal) charger / power converter circuits are very efficient, say 85%.
Stock A700 charger is 12v 1.5A (18W)
THEORETICALLY, stock charger could charge this battery completely in 2.4h.
Commodity USB charger is 5v 0.5A (2.5W)
THEORETICALLY, USB charger could charge this battery completely in 17h.
(Users have reported a 4% charge rate, which would equate to 25h)
Amount of current you can push though connector pins is the usual limiting factor for charge rate.
The charge circuit inside the tablet is designed not to pull more than the pins are capable of carrying.
Assuming battery life of 8h in heavy use (Gaming, Video playback)
Tablet is dissipating 4W of energy on average, almost all of it going to heat