3 ms·

That is not how batteries work. Batteries drain even under minimal usage. My bet is that in 2/3 years this device will stop working already. Just change the b

That is not how batteries work. Batteries drain even under minimal usage. My bet is that in 2/3 years this device will stop working already. Just change the batteries if you AirTag once a year. Especially if you are using an AirTag to keep watch over 10.000 dollar equipment.

Kirby64 2y ago
Lithium batteries (like the 1.5V energizer suggested) have extremely low self discharge. The reason why lithium batteries are used for long life is because you can actually reliably count on them to not self discharge after 20 years. As long as the mAh is 10x the coin cells they use, I’d totally believe the 10 year statement.
alnwlsn 2y ago
Here [0] is the datasheet for the batteries used. 25 year shelf life is spec'd. I have personally run these cells buried underground, and gotten 4.5 years out of 4 of them, though my application is just for fun and likely not as power conservative as an AirTag. [0] https://data.energizer.com/pdfs/l91.pdf https://data.energizer.com/pdfs/l91.pdf
- michaelmior 2y ago
  Okay, now I'm really curious what application you have for a device buried underground.
- 01HNNWZ0MV43FF 2y ago
  Ooh what's the application underground?
  - alnwlsn 2y ago
    So I attend this local annual event that has a time capsule. Each year, we bury one and dig up the one from 5 years ago. This has gone on for several decades, and people are always thinking of interesting things to put in there. I made a little electronics project that is somewhere between "what happens inside a time capsule while it's buried?" and "what if you could wind a watch once and have it still be ticking in 5 years?" I nearly forgot that I made a project page for it: https://hackaday.io/project/160740-low-power-environment-monitor-logger https://hackaday.io/project/160740-low-power-environment-mon... I dug up the first one last year and it had made it to 4.5 years, and I'm actually due to dig up the second one next week.
m463 2y ago
Lots of smoke alarms now have 10 year batteries.
- jerlam 2y ago
  Now mandated in California. No more waking up in the middle of the night and crawling up a ladder to find out which of your smoke alarms decided it was too cold and decided to sing its low battery chirp.
  - michaelmior 2y ago
    Also in New York. Personally I'm all for this even though I think it does make detectors a bit more expensive. Not only because it avoids the need to change batteries, but because it's more likely that smoke detectors actually get replaced at their end of life.
  - _yb2s 2y ago
    Does that fix it or make it worse? If you have 10 smoke detectors and they end up randomly staggered so this happens once a year, and you can't replace the batteries anymore... that seems worse than the old system which completely eliminated this issue if you just replaced them all every year or two on a schedule.
    - jo909 2y ago
      Remember that you are supposed to replace the entire thing because the other components like the sensor or simply capacitors also age. It is a very cheap safety device and simply not worth taking any risks by stretching it to say 15 years instead. The proper way would be to replace them while they were all still fine by making a note in the calendar. There are two cases: Your products are faulty and at least one has not made their intended 10 year lifespan. I'd change them all for better ones. Or They have reached their lifespan and you only noticed because the first one failed. I'd replace them all.
      - _yb2s 2y ago

Kirby64 2y ago

Lithium batteries (like the 1.5V energizer suggested) have extremely low self discharge. The reason why lithium batteries are used for long life is because you can actually reliably count on them to not self discharge after 20 years. As long as the mAh is 10x the coin cells they use, I’d totally believe the 10 year statement.

alnwlsn 2y ago

Here [0] is the datasheet for the batteries used. 25 year shelf life is spec'd. I have personally run these cells buried underground, and gotten 4.5 years out of 4 of them, though my application is just for fun and likely not as power conservative as an AirTag. [0] https://data.energizer.com/pdfs/l91.pdf https://data.energizer.com/pdfs/l91.pdf

michaelmior 2y ago
Okay, now I'm really curious what application you have for a device buried underground.
01HNNWZ0MV43FF 2y ago
Ooh what's the application underground?
- alnwlsn 2y ago
  So I attend this local annual event that has a time capsule. Each year, we bury one and dig up the one from 5 years ago. This has gone on for several decades, and people are always thinking of interesting things to put in there. I made a little electronics project that is somewhere between "what happens inside a time capsule while it's buried?" and "what if you could wind a watch once and have it still be ticking in 5 years?" I nearly forgot that I made a project page for it: https://hackaday.io/project/160740-low-power-environment-monitor-logger https://hackaday.io/project/160740-low-power-environment-mon... I dug up the first one last year and it had made it to 4.5 years, and I'm actually due to dig up the second one next week.

m463 2y ago

Lots of smoke alarms now have 10 year batteries.

jerlam 2y ago
Now mandated in California. No more waking up in the middle of the night and crawling up a ladder to find out which of your smoke alarms decided it was too cold and decided to sing its low battery chirp.
- michaelmior 2y ago
  Also in New York. Personally I'm all for this even though I think it does make detectors a bit more expensive. Not only because it avoids the need to change batteries, but because it's more likely that smoke detectors actually get replaced at their end of life.
- _yb2s 2y ago
  Does that fix it or make it worse? If you have 10 smoke detectors and they end up randomly staggered so this happens once a year, and you can't replace the batteries anymore... that seems worse than the old system which completely eliminated this issue if you just replaced them all every year or two on a schedule.
  - jo909 2y ago
    Remember that you are supposed to replace the entire thing because the other components like the sensor or simply capacitors also age. It is a very cheap safety device and simply not worth taking any risks by stretching it to say 15 years instead. The proper way would be to replace them while they were all still fine by making a note in the calendar. There are two cases: Your products are faulty and at least one has not made their intended 10 year lifespan. I'd change them all for better ones. Or They have reached their lifespan and you only noticed because the first one failed. I'd replace them all.
    - _yb2s 2y ago