I just had an AirTag fail when I needed it. Probably its battery ran down, because after replacing the battery the AirTag seems to work.
However, that makes me worry about my other AirTags, and I can’t find any way to check their battery condition. I can find serial number and firmware version, but no battery voltage clues.
I realize the system is supposed to alert me in time, but it didn’t, or I didn’t see it. What controls this alert? Perhaps I mistakenly disabled it. I hope someday Siri will be able to find things like that!
Pi gave me wrong info about battery status display, probably something has changed. Pi said it would be below the AirTag name in FindMe, where I found serial number.
There used to be a way in Find My to see the battery level but they took it out. One of mine just died recently so I just went ahead and replaced all 4 that came in the same box.
I am pretty sure that opening the Find My app, tapping Items, and looking at each item that there is a low battery symbol when the battery is low. I just changed the battery in three of mine a few weeks ago and I recall I saw this when I looked at them in the Find My app. If you don’t see the battery icon, then the battery is fine.
Interesting, I wasn’t aware of this. It seems an odd interface choice to have it visible sometimes and not others - why do they not just display a percentage, or a green/orange/red icon.
Having said that, I’ve never had an issue with notifications - in fact I replaced a battery a couple of days ago.
Probably because it saves battery and bandwidth not communicating battery state constantly, but only when necessary. But I don’t think that Apple has said specifically other than what is in that Support document.
The nature of Lithium coin cell batteries is that it is very hard to measure remaining lifepsan. Battery life meters typically measure the voltage and compare it against a curve representing how much power is left. But the nature of lithium batteries is that the line is almost horizontal (constant voltage) until the battery is nearly dead, then it sharply drops to zero.
Notice how it is running nearly at its nominal 3v output for nearly 50% of its lifespan (at 125 mAh), then it drops fairly smoothly to 2.75v from there for the next 30% (at 200 mAh). Then it quickly curves down to dead for the last 20%. Any estimate of lifespan is going to be meaningless for the first 50%. And once you hit 80%, you’re on borrowed time.
Given the fact that a meaningful number will only exist for about 30% of its lifespan, showing a computed percentage will be meaningless and/or confusing to people who don’t understand battery chemistry. Better to just report good/bad at some threshold voltage. Which is what the AirTags are actually doing.
(It’s also interesting to note that the battery’s nominal capacity of 245 mAh is assuming a 2v cut-off voltage and a 15 kΩ load. If your device has a higher load (lower resistance) and/or can’t operate at 2v, then your device will fail before you get 245 mAh from it. Something that is clear from a data sheet, but usually isn’t very clear on retail packaging.)
If the battery is dead, then the tag can’t communicate. How could your phone know that the lack of communication is because of a dead battery vs. being out of range?
Logic. If a tag was previously communicating, but has completely stopped for n days, it quite possibly has a dead battery. (“Out of range” of the mesh rarely happens in my experience, the longest I’ve had a tag not be seen by somebody’s device is 2 or 3 days.) I’m confident a heuristic could be developed.
This got changed at some point. Not sure exactly when, perhaps iOS 17?
There used to be a battery indication for every AirTag. Then Apple changed to only showing once it had started alerting to low battery. Not a huge fan of that change myself.
FWIW, there is a battery checker that shows the real-world state of batteries. It’s made by ZTS (ZTSinc.com). I use one (the Pulse Load Multi-Battery Tester MBT-1) pretty close to every day, often testing multiple batteries, including button, lithium, alkaline and so on. If you do a lot of battery testing, it’s worth the $$$ (that is: it’s not cheap. Mine was $100, but they start at $50).
Owned mine for 15 years or so, and never regretted the bucks I spent.
I’ve been through two batteries on each of the Air Tags I own, and each time a battery is about to go, I get a notification on all my devices with Find My that it’s time for a fresh battery. Of course, they were all within range of my devices at the time. Wouldn’t have been much help if a battery gave up the ghost while it was in the hold of an aircraft you were traveling on.
It’s far less dramatic than that. There is a substantial grace period from the moment the warning is first issued to when the AirTags actually run out of power to the point where they no longer work. Once you get that warning, you have weeks left, not hours, to exchange the battery.
My experience, and yours could easily vary, is that the first notification appears about ten days before the battery fails. If you miss that one (and for me, at least, it’s easy to do, since notifications pile up if you’re otherwise occupied), you might only see one notice, two or three days before failure. In at least one case, I noticed neither notice, and the Air Tag was simply not findable until I replaced the battery.
I’m convinced that there is far too much variance in what distinguishes a battery as CR2032. I wish I knew more details about their variations of specifications, and I wish more details were required for their packaging and advertising.
Any general sense of how long the batteries last? I bought 4 about this time last year and they were traveling for a couple months and have then sat in a drawer for the balance of the year. I expect to take them traveling again this winter. Maybe I should just replace the batteries prophylactically.
Mine typically last a little more than a year. But that’s here in the Bay Area with our moderate climate. Mostly Energizer, and never with the “childproof” coating.
The leading “C” means it’s a Lithium-Manganese Dioxide battery (3v nominal per cell)
The “R” means it’s a cylindrical form factor
The “20” is the diameter, in mm
The “32” is the thickness in 0.1mm (3.2 mm)
If you require specifications, you need to look up the manufacturer’s data sheet. Fortunately, all the major brands make them available for download. For example:
In general, the lifespan is going to depend on the chemistry so in theory all CR batteries of a given size should have similar lifespan. But some cheap knock-off brands may put less chemicals in the case, and old batteries that have sat on a shelf for a long time might not last as long as expected.
For Lithium batteries, I wouldn’t worry about it. Keep a few spares in case they die, but otherwise, you should be fine.
This is very very different from alkaline and carbon-zinc batteries. These will leak when they get old and worn out, and the electrolyte can damage electronics. If you won’t be using a device for a long time, remove the batteries and keep them in a plastic bag, so if they leak, they won’t ruin your device.
