It’s cold again here in southeast Michigan, with the overnight low well below zero. A year ago it was the same, which was when I discovered that the ZOOZ ZSE44 has firmware limitations that keep it from displaying below 0° (C or F). For this winter I went looking for a new sensor that might be fine at these temps, and I found one that I’m, so far, liking: the SwitchBot Indoor/Outdoor
Thermo-Hygrometer.
At ~US$31 for a three pack (via Amazon) they are 1/3 the price of the ZSE44, take AAA batteries, and are IP65 rated. The specs also claim they work down to -40°C (-40°F) with Lithium batteries. Basically perfect for outdoor spaces including attics, crawl spaces, etc.
I installed this side by side with the ZSE44 with the solar radiation shield on the back fence, and as hoped, it’s reading well below zero and working fine. I also put the other two (from the three pack) in the fridge and freezer to see how they’d do there, and while the freezer doesn’t get as cold as it currently is outside, it was a good preview of data before the temperatures dropped. And all three currently are at 100% battery.
Now that we’ve had our first well below 0°F temperatures of the season I can say that yes, the SwitchBot sensor is working properly, with more frequent updates.
When initially setting up Home Assistant its purpose was to log temperature and humidity at various points around the house. I started with the cheapest sensors available at the time — Aquara Temperature and Humidity Sensor — but after a couple years have passed I’m finding these a bit disappointing. The CR2032 battery life isn’t great (even indoors they last about 8 months), and I’ve had a few of them just die. While they are small, the size benefits don’t outweigh the battery and longevity hassles. The Zigbee connectivity is pretty simple and mostly works, but when the battery or device dies it just kinda… falls off the network and works/rejoins (even after a battery swap) unreliably. I think I’ve disposed of three in the last year.
The biggest downside to these SwitchBot sensors is they use Bluetooth Low Energy (BTLE) for communication. This does not have nearly the range of Z-Wave, which was my original reason for putting the ZSE44 in the back yard.
Thankfully Home Assistant can use Bluetooth Proxies (networked remote BT sensors), and the Shelly 1 — a UL-listed WiFi-controlled smart relay — is one. I already had a few of these around the house to control lights fixtures, so via the proxies I’m able to get enough BTLE coverage to pick up the sensor along the back fence and the ones in the fridge. It’s no Zigbee or Z-Wave or Thread-like self-healing mesh, but so far it’s working well. And really, with the devices’ fixed locations, there’s not a ton of practical difference between setting up a mesh network with well-planned routers (Zigbee) or repeaters (Z-Wave) and deploying BTLE proxies.
I’ve also picked up two of the SwitchBot Meter Plus devices which is a temperature/humidity sensor with an LCD display that runs off of two AAA batteries. It’s not as robust as the Indoor/Outdoor sensors, but is perfect for somewhere I want to see the local temperature visually and log it in Home Assistant; indoor uses. In years past I’d place temperature/humidity displays like this around the house so I could see some data, and these are basically the same, except with logging to Home Assistant.
Long-term, as they fail, I could see myself replacing the remaining Aquara sensors around the house with these. Even the couple of ZSE44 sensors I have may get replaced with these (particularly the one in the back yard). But, for now, I’m just glad to know how far below 0° it really is, and have record of this, because data is nifty.