Smart lock batteries do not usually die suddenly. They warn you for weeks first, and almost everyone ignores it. However, there is a second cause that nobody mentions, and it is mechanical rather than electrical.
Cold is the obvious factor
Battery chemistry slows in cold weather, so capacity drops. Consequently a lock that lasts a year through a mild summer may manage noticeably less through an Ottawa January. Furthermore, an exterior keypad sits fully exposed. Therefore the practical advice is to change cells annually in autumn rather than waiting for a warning.
The cause nobody mentions: a binding door
If the door has dropped or the frame has swelled, the bolt drags against the strike. Consequently the motor draws far more current on every cycle. Therefore batteries that should last a year die in months. Moreover the lock eventually fails to throw at all, which people blame on the electronics.
How to check
Throw the bolt with the door open, then closed. If closed feels noticeably harder, the strike needs adjusting. Consequently fixing that alone often doubles battery life.
Warning signs before it dies
Most locks beep differently, flash a colour, or slow noticeably when low. Additionally the keypad backlight dims. Consequently there is usually two to four weeks of notice. However, some models only warn on the app, which is useless if notifications are muted. Therefore know how your specific model warns you.
If it dies anyway
Use the mechanical override, which is why we insist on models that keep one. Alternatively, many locks accept an external nine-volt battery held against contacts on the underside, which powers them long enough to enter a code. Consequently a dead lock is rarely a genuine lockout. Above all, keep the override key somewhere other than inside the house.
Questions we get about this
How long should the batteries last?
Often a year. However, cold and a binding door both shorten it.
Why do mine die so fast?
Frequently a misaligned strike making the motor work harder.
Is there a warning before they die?
Usually two to four weeks, via a beep, a light or the app.
Can I get in with dead batteries?
Yes, with the override key, or by jump-powering the contacts on many models.
What batteries should I use?
Good-quality alkaline. Lithium performs better in cold but check your model supports it.
