Freezer temp sensor, local

[dire rampart]

I'm planning my home automation build right now, one of the pieces I'm struggling to source is a temp sensor for inside a deep freezer.

I lose internet multiples times a year for multiple days due to weather, so the requirement is that it be local only.

I'm not in a position right now to run MQQT locally in a Docker container, maybe in the future when I get a better homelab setup.

I'm currently considering the ThirdReality temp sensor lite (no screen) because it uses two AAAs, so I can put it in a bag to save it from condensation and use Lithium batteries that do better in the cold, which should more than solve the issue of putting a button cell sensor in a freezer.

Recommendations?

[fringe tartan]

Maybe the temp-1 from Apollo automation? @dense hawk is this a good use case?

[dire rampart]

That actually looks great and didn't come up in any of my searches. I was hoping for a remote probe to keep the battery and compute out of the freezer. Currently out of stock, do they restock often?

[blazing adder]

Well you've covered the thing I was going to say, which is Li-MnO2 batteries don't work that well in the cold, and correctly identified that the Li-FeS2 AA/AAA are considerably better.
But keeping the electronics out of the freezer entirely is definitely the better choice.

[jolly ruin]

My tuya zigbee sensors work fine in the freezer 🤷

[fringe tartan]

Yes they do.

[dire rampart]

Model and battery? Battery life?

This is the only discord thread that's gonna come up (currently) if someone searches for this (based on my searches before posting) so I'd like to keep the conversation going

[jolly ruin]

It has a CR2450. It has no real model number but it's this: https://www.aliexpress.com/item/1005002362873744.html
I'm not completely sure about battery life but I'd say at least 6-12 months.
I also own ones with 2 AAAs. They all work fine for me.

[dense hawk]

frankly i like the inkbird BLE ones and our temp sensor technically doesn't exist yet but it works great. but if he wants long battery life and a tiny device not a temp probe, then the inkbird BLE ones like this are hard to beat.. https://amzn.to/3C6P9A8

[leaden saddle]

Check out SensorNode project - you can mount the SensorNode unit outside the freezer, and run a long temp sensor into the freezer. https://tnbtechnologies.com/sensornode

[dire rampart]

That's very interesting, but not available yet. I emailed Apollo about the Temp-1 and they say a new one will be available in a few weeks. Since I'm not purchasing until December I can wait to see what they come up with

[leaden saddle]

SensorNode kickstarter in Dec

[bleak mulch]

I have been using three switchbot indoor/outdoor https://www.amazon.co.uk/gp/product/B0BVLYPYT1/ with the switchbot bluetooth integration. They don't need a hub or any cloud service

Two are in freezers, in polythene zip bags. The other is hanging unprotected in a shady part of the garden.