Every morning the garage motion sensor shows as unavailable and I have to walk out and press the button to rejoin it. It works perfectly all day. The garage is about 12 metres from the coordinator with one brick wall in between, and there are two mains powered smart plugs on the way. Nothing else on the network misbehaves. Is 12 metres just too far, or is something specific happening at 3am?
Second most likely thing given the time of day: temperature. Coin cells and AAA cells lose a chunk of usable voltage when they get cold, and an unheated garage at 3am in the cold half of the year is the coldest point of the day. The sensor browns out, misses its check ins, and gets aged out.
If the failures started when the weather turned, that is your answer. Lithium AA or AAA cells hold voltage far better in the cold than alkaline.
Cold is easy to confirm after the fact if you log the raw voltage rather than the percentage. Mine visibly dips overnight on the garage sensors and recovers by mid morning, and the dropouts sit right at the bottom of that curve.
Alkaline in a cold garage is a bad time generally. I switched every outdoor and garage sensor to lithium two winters ago and the mystery dropouts stopped even where I never changed anything else.
Also check channel overlap while you are in there. Zigbee and 2.4GHz wifi share the band, and if your access point sits on a channel that collides with your Zigbee channel, marginal links go bad first and the garage will be the most marginal link you have. Zigbee 15, 20 or 25 paired with wifi channel 1, 6 or 11 respectively keeps them out of each other's way.
One practical note: a metal garage door is a large moving reflector. If the door is closed at night and open during the day when you are using the car, you have a different radio environment at the exact times you are describing. Mine improved a lot when I moved the sensor 40cm away from the door frame and off the metal.
Just buy a wifi sensor for the garage and skip the mesh entirely. Zigbee range at that distance is always going to be marginal.
12 metres with one wall and two routers in between is comfortably within Zigbee's range. Swapping protocols to avoid diagnosing a nightly pattern usually just moves the problem onto wifi, where battery life gets much worse.
@yaml_yeoman · 4mo ago · 3 replies
Something at 3am is the clue, so look at what turns off at night before you look at range.
Battery sensors are end devices. They pick one router as a parent and stay attached to it. If the router they picked is a smart plug that you switch off overnight, or that is on a schedule, or that gets power cycled by an automation, the sensor loses its parent and has to find a new one. Some firmware rejoins fine and some sits there sulking until you press the button, which is exactly your symptom.
Check which of those two plugs the sensor is parented to (the network map in most controllers shows it), then check whether that plug is switched at night. If it is, either leave it powered and switch the load a different way, or use a dedicated mains repeater that never turns off.
Second suspect if that comes up clean: a nightly restart of the controller or the container. That drops the coordinator for long enough that weak links do not recover.
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@cache_invalidator · 4mo ago
This is such a common trap. My hallway lamp plug was the parent for four sensors and it was on a sunset to sunrise schedule. Everything downstream fell over at 6am, which took me a month to connect to the lamp.
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@null_pointer_ok · 4mo ago
Worth adding that some cheap plugs technically route but do it very badly, with a routing table of about five entries. If you have a lot of sensors, one purpose built repeater beats five plugs that all think they are routers.
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