There’s a lot of different “lithium” batteries, Li Ion, LiFpo4, LCO, LCA, etc… so just a friendly FYI, it’s not very helpful to anyone that wants to duplicate your project and they go to buy “lithium” batteries. Li Ion are by far the more common so, I’d imagine that’s what you got.
Just a friendly tip but, check out LTO cells (lithium titonate). They are a bit more expensive and have similar specs to Li-Ion except 2 and those are, they are far better in cold applications than any of the others and secondly they can be recharged about 10x faster.
unfortunately, I see people do it pretty frequently but, good for you and having a bit of sense. IMO power metering w/reed switches on the doors is just as effective except doesn’t ruin any warranties or appliances themselves…
All my life it’s never been “need to know” or critical information regarding the temp in my fridge/freezer. It’s either working properly or not and it’s still true today. I don’t need the internal temps to know something is out of whack and needs attention therefore my DeWalt drill can stay in the tool box.
Sounds like OP found a solution, but I will add my $0.02 for others curious about this.
Some other people here on the forums told me they were using Aqara temperature sensors, which I could not believe either. But I tried it and it has been working fine for me so far. This was pretty recently, but I just looked and it does look like it is eating the battery at a much higher rate (or perhaps, the battery level is showing lower than it should due to the temperature?).
For the people who are dead set on drilling, the door seems to be the safest place, usually. As the coils run around inside the sides and the back. I learned this while looking into building a ‘keezer’ recently.
A bit of caulk I think would be the easiest thing to fill in the gap for those who want to simply run the wire under the gasket around the door.
First of all, dont sell yourself short! That was worth atleast $0.05 cents. It could have been 0.10 cents but just like you dont feed wild bears or alligators, you shouldnt encourage drilling holes in freezers!
IDK, to each his own I guess. Like i mentioned above, theres more than one way to skin this cat and mine didnt involve drilling holes in appliances or taking on more responsibility with buying, stocking, replacing, or recharging batteries.
As far as “eating the battery” its anyones guess whats going on when you dont include any helpful details such as, what type of battery? Fridge or freezer, etc.
For future reference, please dont feed the alligators or encourage the drilling of holes in appliances! Its the Christian thing to do…
Sorry to say, but I am neither unknowledgeable about batteries, nor imprecise in what I said. I know there are many types of batteries, an all the ones you refer to are rechargeable ones, which indeed have all kinds using lithiom ions. The ones I talk about are not rechargeable.
What I specified: “Lithium” (the metal) IS the exact reference by they are sold, by various brands. So you can go to a shop and ask for them. You probably know them from CR2032 and other small ones, but they are sold in aa or aaa size too. So it is exactly what I meant. I was trying to avoid referring to specific brands or shops, but here are some examples:
Many comments in this thread talking about the justification for temperature sensors. Here are my two legitimate reasons why to invest the additional effort:
It is good practice to control the fridge power setting (in older models) depending on load and season of year. The best way to do that while being mindful of energy consumption is to have temperature sensors and automations to warn when the recommended levels are exceeded.
The real home automation nerd will sense and control almost everything in their house. It’s fun, it’s cool, it’s mostly unnecessary. Just let them be
My solution was to add two DS18B20 to a Sonoff Basic and wire them between fridge and door insulation. Working without issues for the last couple of yours in two homes.
Bingo! That was basically my point except Im leaning towards completely unnecessary. If for some reason it is actually necessary for someone then they most likely need a new fridge, not some cheap temperature sensors.
You my friend did not get my point: I disagree.
I think it’s very useful to do long-term automated temperature observation to tackle drift and open doors.
The argument to simply buy a different fridge is weak as the existing fridge (without display or beeper) is not automatically bad or cheap.
I use the sensor for my garage refrigerator. Many refrigerators do not control the freezer correctly if use in a cold environment. I add a heater element (10W bulb) that goes on if the Freezer goes above 1F. Works great and the refrigerator is not old, just not designed for this use.
Not necesarilly. If door is open just a bit then compressor might be able to cope with it, so temperature will stay low enough, it’s just that motor will (almost) never shut off, so enegry consumption will increase, as well as ice will build up inside. Monitoring with energy measuring is also unreliable in this case, since you don’t know how much longer motor would have to run to indicate open door - longer motor run can also happen when you put more things inside at the same time.
The most reliable door check is via light switch. If you don’t want to mess with that then additional magnet switch is also an option.
I like your logic a lot, and it makes much sense. Also using light (light sensor?) or magnetic reed switches (very simple) are all good solutions too (although not for power loss or breakdown - a light could still work when the compressor fails, not that they do very often). I think you’re right in that there’s multiple ways to monitor this.
However, in my personal experience I have found that the inside temperature, at least in my freezers (I had 5 monitored this way once), always raises rapidly when the door is open even the smallest amount - convection on upright freezers sucks the cold out rapidly (Would be less for chest freezers I guess). I have an alert that notifies my phone whenever the temp in those freezers rises above -10c and it’s saved my bacon several times. (literally)
It’s also reassuring to be able to monitor the inside freezer temp during a power cut and know exactly when you’re going to need to break out a generator.
I don’t personally monitor my fridge because it doesn’t matter so much if stuff in there gets a little warmer for an hour or two, someone’s always in or out of it in that time so open doors tend to get noticed much quicker than the freezers.
I use ESPHome.
Inside my fridge I have a BME280 for temperature and humidity and a BH1750 for lux measurements. They are connected to an ESP outside the fridge so the fridge doesn’t impact WiFi and so that I can keep it powered all the time. Plus I don’t have a constant ~ 0.5-1.0W heat source in my fridge.
Sensors are connected with 4 tiny wires that runs out the fridge to the ESP. The wires pass through the door gasket which still manage to “seal” around the wires.
Whenever the lux readings are above 0 I know the door is open and I use that to trigger various automations.
Makes sense. I also use esphome a lot (5 of them now, they’re kind of addictive), but for freezers I use either onewire or zigbee using an 18650 battery (coin batteries really don’t last for long at -20c but these are good for 6-12 months). In practice, I’ve found zigbee works just fine through a freezer door (and three masonry walls) but obviously any barrier does restrict signal. I did have wires through the seal, but it wasn’t as satisfactory for me personally as having everything inside and easily transferrable. One thing I do like about stuff like this is that there is no one right way of doing most of it and it allows us all to play around and learn for ourselves.
this post!