The PX3 features a lithium polymer ("LiPo") battery. It's best to charge up your PX3 headset all the way before first use.
How to Recharge your PX3 headset:
Plug the headset into the USB "CHARGE" port on the transmitter to charge for a minimum of 6 hours.
You may disregard the LED on the headset. The headset's LED will go out when the headset is charged up to 75% of its capacity. At this point you could disconnect it and use it, but the headset will not be fully charged. We recommend that you charge it up all the way and then use it.
Always connect the headset to charge when the battery runs low, even if not using the headset afterward.
Make sure to charge the battery for at least 4 hours before storing the headset or not using it for a long period of time.
Never store the unit in temperatures above 113°F/45°C. Store the battery at room temperature (72°F/22.5°C) and at humidity below 75%.
WARNING: Never let the battery run very low and then put the unit in storage, as this may cause irreversible damage to the battery and issues such as shorter battery life, or the battery no longer charging correctly.