Abnormal drain of the Apple Pencil Pro

Have you enabled Find My for your Apple Pencil? If so, this feature being active will shorten the time that the Pencil can be separated from the host iPad for charging.

It is generally recommended that the Pencil is always docked with the host iPad whenever it is not being actively used - as this will ensure that the Pencil's battery is automatically maintained at optimal charge by the iPad.

Your Pencil will come to no harm when docked with your iPad for extended periods. The Pencil battery will not be over-charged, but will be protected from potential damage from deep discharge should the Pencil be if inadvertently left isolated from the iPad.

Consider that a completely motionless Apple Pencil will automatically enter its low power mode - where its Bluetooth radio is suspended - and will consume very little power. However, when movement (however slight) is detected by the Pencil accelerometer, the Pencil will return to its active state and consume power from its tiny battery.

As such, when not docked with the host iPad to maintain the Pencil's battery charge, the slightest movement will wake the Pencil to its fully active state. When the Pencil is being carried in a pocket or bag, separately from the host iPad, the Pencil will be fully active and will quickly deplete the Pencil battery.