1. Act on the warning
Most smart locks warn you through the app, a beep or a light when the batteries are low. Change them as soon as you see the warning, not after the lock stops working.
2. Use the right batteries
Many locks take four AA alkaline cells. Fit four new ones of the same type at once, and check the manual for the exact number and type.
3. Look for a 9-volt backup
Many smart locks have a 9-volt terminal on the outside. Touching a 9-volt battery to it can power the lock for one entry. Your manual shows whether your lock has one.
4. Keep a physical key
Always keep a mechanical key or a backup code somewhere safe. A dead battery shouldn’t lock you out, so give a spare key to someone you trust.