If the Xiaomi Focus Pen isn't at 100% battery even after charging overnight on the Xiaomi Pad 7 Pro, it's due to the following factors:
1. To conserve tablet power, charging stops once the Xiaomi Focus Pen is fully charged. If it remains magnetically attached, it will only recharge once its battery drops to 80%;
2. If needed, you can remove and reattach the Xiaomi Focus Pen to the tablet to immediately resume charging.
These features are designed to optimize battery health and energy efficiency, ensuring both devices last longer over time.