How can you tell when the battery is charging?
Your indication that the internal battery on the joystick is charging IS the red light, which in some configurations
may turn to different colors as charging progressses, but if you note no color change, and/or if when you disconnect the joystick from the power, the light either does not stay on or the stick does not operate independantly of the power source, then the internal battery is defective, has exceeded the number of recharges
cycles and/or is fried.
Buy a new set of batteries for all sticks at the same time and play on.