I have a manual battery though.
There are 4 reasons for the yellow flash:
1) You took a drag/held the button for to long. Over 5 or 8 seconds, whatever yours is set for.
2) The batt needs recharging.
3) You have just pluged it into the charger, it sees the charge and will start charging.
4) Continuous flashing - there is a short. This can happen when you put it on the charger, or release the button. It will contunine to flash. You will need to clean the contacts. Ussally the ring between the center (pos) and the thread (neg) is bridged by a buildup of ejuice that is causing a short.