Rechargeable batteries have a lower operating voltage around 1.3V v/s 1.5V for alkaline batteries. Lock circuits are calibrated to cut off lock operation when the voltage falls below a certain threshold, e.g. 1.1V. The voltage discharge curve of a alkaline battery is longer so it takes longer to get to 1.1V where as rechargeable batteries get to 1.1V much faster hence the lock circuit powers down much faster. For that matter Lithium batteries have a much flatter voltage curve so they take longer to get to 1.1V (but i’ll happen much faster in the end like in a few hours v/s days) so they are able to extract the most juice from batteries before the lock does.
To make things more interesting is the difference between no-load and load voltage drops. When the lock draws a large amount of power from the battery (e.g. when operating the deadbolt), it causes a temporary voltage drop due to internal resistance of the battery. Rechargeable batteries have a higher voltage drop (it varies depending on chemistry, NiCD or NiMH, NiMH are better of the two) under heavy load than alkaline batteries (Lithium have the least), so it very likely that when operating the deadbolt the lock will suddenly “die” when using rechargeable batteries. Infact some locks like Schlage BE469 have a huge current draw and cause this phenomena even with alkaline batteries and so it’s recommended to change deadlock batteries at 60% instead of waiting for it to go lower. This is explained here and you can find some recommendations about it here.
Due to difference in battery chemistry/voltages and the lock chip cut voltages, rechargeable batteries are not recommended to use with locks.
Not that this helps, but my Kwikset 914 has batteries that are at least 4 months old. I am using high quality lithium ion rechargeable batteries. The door lock is used about 8 times a day (via SmartThings) during the week and more on the weekends.
The 914 is about 5 feet away from the SmartThings v2 hub.
Edit - they are NiMH batteries.
RBoy
(www.rboyapps.com - Making SmartThings Easy!)
43
Lithium ion batteries are 3.6 to 4.2v, your lock needs 1.5v batteries. You’re probably frying your circuits. You should ONLY use 1.5v batteries like an Alkaline battery or at best a 1.5v Lithium battery and never a Lithium Ion battery.
RBoy
(www.rboyapps.com - Making SmartThings Easy!)
46
You may not get the full use of your batteries, see my post above and the link s in it which explain why, it’s related to the battery voltage of NiMH batteries which are lower than Alkaline and Lithium 1.5v so the circuit shuts down faster, depending on the voltage and load put on your NiMH batteries. When the motor runs it puts a heavy load on the batteries and if the battery can’t supply it the voltage tanks and it shuts off the circuit to the lock.
REF, for a steady state small current draw voltage curve:
Under heavy load the voltage will drop faster for lower quality batteries.
Yes, I read your post about how alkaline batteries are better. Perhaps in this application these batteries work well. The last time I swapped out the rechargeable NiMH batteries was in April 2019. Again, the lock is locked and unlocked from SmartThings 6 times a day and more on the weekends.
Just went through the same thing with the kwickset 888 called customer service and they sent out a brand new one and it seems to work fine with the old lock i was changing batteries every 2 days
I have a 913 that was eating batteries even though I was using the best quality fresh dates energizer batteries available. I’m not connected to anything wirelessly and Still the batteries last about two weeks. This lock is well mounted and turns easily with no resistance. The lock is in my pool house so it maybe gets used twice a day. I want to say they have a very professional phone support and they have been kind enough to send me not one but two replacements but the result is the same. I tried using the key for a week the last time and it still ran down without the motor being used. Bottom line is there is a serious battery drain issue in the 913. I’m going to have to seek another brand,
Do yourself a favor and get rid of that lock! I swapped mine out for the schlage equivalent door handle zwave lock and have not had a problem since. I also heeded the previous advice in this thread and kicked the lithium batteries.
I too, just experienced the same with the 888 model. It was draining my batteries, brand new every 2-3 days!!!
I contacted their support number, created a case, did some over the phone troubleshooting and determined it is a faulty motor. They’re going to review and checking stock inventory and promised to ship one out to Me.
Thank you for your input, it helped Me out big time.
The good news is that a Kwikset Smart Lock will tell you when the battery is low several weeks before it runs out. A red light indicates that the device’s battery is low.
Keep in mind that your key will still work if the lock dies before you can replace the Kwikset Smart Lock battery.
I don’t know if it’s an option for you but I highly recommend the schlage version of this lock type. I switched mine after my kwikset drained out a new set of batteries and have never looked back. The amount of time you will spend wiring this lock through the doorframe will likely end up costing you more in time than just buying a lock that works well. Jist my two cents. The schlage locks have been rock solid. I will never buy another zwave lock type.
RBoy
(www.rboyapps.com - Making SmartThings Easy!)
56
Schlage and Yale are generally very good quality locks with solid chipsets. We’ve used over 50 models over the last decade in all kinds of environments (rain, run, snow etc) and some have failed but many are still running.
Kwikset locks tend to experience zwave chipset failure after a few years leading to a battery drain, but some models allow you replace the zwave module so it could be a quick fix.
Schlage locks have modules which are soldered in but are very reliable in general. If they do fail customer support is quick to replace the lock. However some of these locks do have a firmware problem in their zwave module (which’s chal ge refuses to fix even in their newer zwave plus chipsets) which prevents them to working properly where there is mesh packet loss. They are also notorious for requiring repeaters to buffer packets as they are susceptible to mesh timing issues.
Yale lock by far have been the most stable and reliable locks. Some of the very early zwave modules had a battery issue but the newer zwave plus modules are rock solid and tend to have the best battery life as well as the best mesh connectivity leading to fewer problems than other brands. Also they have interchangeable modules so you can replace a zwave with a ZigBee or a WiFi module.