This has happened to me. If it still doesn't charge up after what you've tried, do this:
Make sure that the battery is plugged straight into the charger. When I did that it wouldn't charge it through my transmitter at first; too drained. As soon as I took my battery out of the tranmitter my charge light came on. I just left it like that for about an hour and then put it in the transmitter and let it charge all night. Full charge in the morning. I use a stock charger also. Hope this helps.
Joe