What happens if a smart lock battery dies?

What happens if a smart lock battery dies depends on model, but you will not be permanently locked out if you have prepared backup options. Most smart locks give low battery warnings weeks in advance via app, blinking light, and audible beep when battery below 20 percent, giving time to replace. If battery fully dies while door is locked, you cannot unlock via app, code, or fingerprint because electronics have no power, but most smart locks have backup methods, external 9V battery terminals on bottom where you hold 9V battery to provide temporary power to enter code, USB-C emergency power port for power bank, or included physical key override that works even with dead battery. If door is unlocked when battery dies, it stays unlocked, which is security risk, so replace quickly. Some locks have battery inside interior side so you can still manually turn thumb turn to exit even if dead, you just cannot lock electronically. To prevent, replace batteries every 6 to 12 months, use lithium batteries for cold weather, enable low battery notifications, and keep physical key with trusted neighbor or lockbox. Planning ensures dead battery is inconvenience not emergency.