Schlage Door Lock Battery Died Suddenly

[RBoy (www.rboyapps.com - Making SmartThings Easy!)]

What is your lock model?

If it’s the Schlage Connect Deadbolt/468/469 series then there’s a bug in the firmware of the lock and the way it reports battery. Having said that, there’s also a bug in the stock ST device handler in how often it checks the lock for battery updates.

The first issue need more explanation (see below). The second issue has been fixed by us in the [RELEASE] Universal Enhanced Z-Wave Lock Driver for Schlage, Yale, Kwikset, IDLock, Popp, Danalock, August Pro, Keywe, Philia, Samsung device handler

You should avoid using rechargeable batteries for these locks since they have a lower voltage (1.2v - 1.3v) than alkaline batteries (1.5v) and when the voltage falls below a certain threshold the lock suddenly shuts down.

Similarly it’s recommended to change the Alkaline batteries when it reaches 60% on these locks (see this post [RELEASE] Low Battery Notification with Customizable Alert/Warning/Monitor, Configurable Thresholds and Device Monitoring Alerts for recommended battery levels).

The lock tends to misrepresent how much power is left in the battery due to a firmware quirk. It measure the battery voltage and determines the left power. However when the lock reports about 60% battery life, when the lock deadbolt motor operates, it has a huge current draw on the battery (lower the voltage higher the current draw required to operate the motor which in turn causes a bigger voltage drop, it’s a run away effect). This causes the battery voltage to drop suddenly ( see this post on battery voltage curves [DEPRECATED] Blink Camera Device Handler with Motion Sensor, Live Video Streaming, Integration with SmartThings/SHM, Temperature, Signals and Push Notifications - #1157 by RBoy ). When this happens the voltage falls below the minimum operating voltage of the lock and it shutdown suddenly. This is why it’s recommended to change the battery at 60% on these locks when using alkaline batteries.

If you’re using Lithium 1.5v batteries, you’ll get double to triple the battery life from these locks BUT note that the voltage curve on these batteries are drastically different from Alkaline batteries and are VERY flat. The lock firmware isn’t designed to handle these curves so what happens is that when the lock reports 97% that’s about the time to change the lithium batteries otherwise the same voltage load issue kicks in and the lock goes dead. See this post on Schlage locks and lithium batteries Battery Life for smart Doorlocks - #29 by RBoy

Also see these post for more insight in how battery and SmartThings work:

Battery reporting, still a problem in 2018

Good write up. Let me try to add a few points from how ST and the DTH’s work with some devices. If you have a Z-Wave device as per the specs it defines two alerts before the battery dies. First one is low battery and other one is critical battery (depends on type of device). Now comes the tricky part: The specs don’t define what is low battery and what is critical battery. Some devices report low battery as 30% others as 10%. Same for critical battery. So what ST does is by default in most handlers when it receives a low or critical battery it sets the level to 1%. So if you see a device showing 1% it’s not because the battery is at 1% it’s because it sent a low or critical battery alert and the DTH set it to 1%. If you have custom DTH then those may do a better job of defining how it h…

Kwikset 914 vs 916 Recommendations?

Part of the reason is the way batteries work. Standard alkaline batteries have a higher voltage discharge curve then say lithium batteries. So actually when the battery level is down to say 70% it’s running low “power”, when I say power I mean the ability to draw amps from the battery. Now consider a deadbolt, it has a pretty heavy duty motor that draws a lot of power. As a alkaline battery at 70% when the motor tries to “draw” that enormous amount of power/amps from the battery the voltage takes a tank and this causes the electronics to shutdown the lock. On the slip side a FE599 which is a magnetic actuator lock needs far fewer amps to achieve a lock/unlock hence it can go onto about 50% when finally the magnetic draw on the actuator causes the voltage to drop and shutdown the lock. Th…