You should remove the battery in your power razor when vibration slows or ceases. Don't leave a depleted battery in your device. Always replace batteries in a dry environment and dispose of batteries in accordance with local regulations.
Insert an alkaline battery, such as Duracell, correctly and do not short circuit. If your battery leaks, wipe the razor clean with a damp cloth and wash your hands. If any material gets into your eyes, contact a doctor immediately.
Keep batteries away from children. If swallowed, consult a physician at once.