How can I tell if the tank is full when the volt says 14.8 - 16.2 ? Monday I must have forgotten if I had change battery after flight, when I try to fly again the arming sound on ESC and timer, but when I try to start all I got was a shutter on the prop then nothing.  I guess I'm still new to E - flight, as Sunday I had 6 flight and all were perfit time of flight about 5.3 min. and had 25% left in tank, according to FMA 10 cell pro. charger....

I am not sure what you are using now, but a fresh 4s lipo battery should have something around 16.4V or higher (16.8 when it comes off the charger)---or 4.1 to 4.2V per cell. It is basically a depleted pack at 3.7V per cell or 14.8V for a 4s.

All that being said, I have been there and done that. Now when I remove a pack from the plane, I make sure I put it away from the fresh packs.

Larry
There is a simple way to "mark" your charged batteries. It was posted on this forum
some time ago and it works. Get some small rubber bands and put one on each battery when you charge it. Then when you put battery in for flight remove the rubber band. If you forget to remove it before you fly you can always remove it
after flight. I have adopted this in all my practice flights.
 Walt