If you find your vest is not holding a charge/dying prematurely, you will need to recondition the battery.
You can do this by first setting the vest to Game # 9, put the time to infinite and hit play. Let the battery drain.
Once it is dead, plug your vest in to charge.
When the charging cycle is complete (the red light goes off), unplug and replug the vest in for an additional charge.
You should complete this process of unplugging and then charging again an additional 4 times to ensure your battery is fully reconditioned.
Each unplug & replug will take about 2-4 hours per session.