Kwikset Locks, battery reporting, lithium batteries

Posted on
Mon Jul 30, 2018 10:30 am
dduff617 offline
Posts: 398
Joined: Jul 05, 2006

Kwikset Locks, battery reporting, lithium batteries

Just relaying a bit of info I discovered by accident recently:

I have a few Kwikset locks, model 912, which I believe is the same as 910 with the Home Connect module (Z-wave interface). I tried using Lithium AA's in one of my locks, thinking that Lithiums might fare better in terms of both longevity and resistance to cold temperatures. They seem to work ok, but except that the lock reported a steady 80% battery level for multiple months via Indigo right up until the time when it stopped working. At that point (and not earlier), I confirmed that the battery level in Indigo dropped to zero.

The odd thing is that I think the lock was trying to give me signals (via beeps and flashes) that batteries were low whenever I tried to use it over the last few weeks. I heard the beeps, checked reported battery levels in Indigo, it reported battery at 80%, so I assumed the beeps were reporting some other type of warning or error condition.

So I'm not sure how/why the lock unit itself seemed to know the battery was low, but somehow the displayed battery level in Indigo was Indicating a healthy battery and not updating. I would be interested to understand the deeper cause of this. A guess on my part is that the lock was measuring a voltage that was out of its idea of a reasonable range (in this case, perhaps due to difference in voltage range for lithium vs. alkaline) and therefore was not sending any battery level update to Indigo. ... and perhaps absent any valid update, Indigo just kept displaying the previous value?

Admittedly, my guess is based on a rather sparse set of data. In the past few months, I've only seen a total of three different battery values from my two locks: 100%, 80%, and 0%. I'll watch more closely to ensure that the same lock behaves more reasonably over time with the new set of alkaline's I just installed.

Posted on
Mon Jul 30, 2018 11:00 am
lanbrown offline
Posts: 423
Joined: Sep 26, 2017

Re: Kwikset Locks, battery reporting, lithium batteries

The lithium batteries have a higher initial voltage but it drops off and then is more of a linear drop until it is dead. That makes it harder for a device to check the battery level since it is different than an alkaline. So if they use voltage to check the health of the battery, a lithium will give it false readings.

Posted on
Mon Jul 30, 2018 11:15 am
jalves offline
Posts: 470
Joined: Jun 16, 2013

Re: Kwikset Locks, battery reporting, lithium batteries

Interesting info. I'll have to pay more attention to my two Kwikset locks to check this behavior.

Running Indigo 7.1.1 on a 27" iMac (mid-2017), 8G memory, 1T Fusion Drive, OS X 10.13.6
Jeff

Posted on
Mon Jul 30, 2018 11:34 am
lanbrown offline
Posts: 423
Joined: Sep 26, 2017

Re: Kwikset Locks, battery reporting, lithium batteries

Here is a great article on it:
https://www.dealnews.com/features/Test-Results-That-Will-Change-the-Way-You-Buy-Batteries-Forever/449005.html

Initial voltage, notice the much higher initial voltage:
Image

Then this is voltage over time as the battery is drained. The lithium is the red graph and notice that it stays higher than the other batteries. So depending on what the lock used to check the battery strength, this would explain the behavior that you saw.
Image

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