I have had a few Multipurpose Sensors in my foyer doors for about a month. The reported battery life on one of the sensors has fluctuated from 56-67-56-67-78-67-11. 11 !!! This is a door that maybe gets used once or twice a day. Any ideas? I went from 67 to 11 in 3 days. Even 67% seems low for just a month of usage.
I believe ST devices actually have battery level steps hard defined so you won’t find the battery going 99, 98, 97 etc. Goes from 100 to 8x and so on, can’t remember the increments but you can search for it here; was years ago we discussed this.
Also note temp has a lot to do with batteries. Warm sunny front door Multi or car presence sensor can be double what it is when night falls in the off season.
My car will read 25% in the day and 1% at night in the winter. My front door lock will be 100% on a battery change and 50% a week later after a couple of steps and cold nights.
Just jumped back to 67% battery. I don’t get it.
I think like Daven mentioned it’s likely temp driven. The lithium cell batteries are very susceptible to changes in temp. I found this out the hard way earlier this week because my Smartthings multipurpose sensor stopped working and I thought the unit died since it’s only a couple month old. Turns out the lithium cell battery was to cold. I was using this device in my chest freezer for open/close and temp. Wellllll I found this out
“The performance of all batteries drops drastically at low temperatures; however, the elevated internal resistance will cause some warming effect because of efficiency loss during use. At –20°C (–4°F) most batteries stop functioning.” from here: http://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures
For me it turns out the freezer would cycle below this and eventually come back up to 0. So it lasted a couple of weeks and couldn’t take it anymore. I pulled the battery and sensor out and let it warm up for 24 hours and now the sensor will power back up. The battery only shows a max of about 67% though. If yours is attached to a steel clad door and it’s colder out that cold be radiating cold to the sensor and affecting your battery life. Honestly though most of my other sensors that report battery % seem to bounce around a lot.
Steve, I’m 99% sure you are correct and this problem is related to the temperature. The sensors are much more accurate/consistent now that temps have gone above freezing outside. Good to know the battery performance isn’t as bad as I thought.