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Comment by bmilleare | Hacker News Reader

Automating such a narrow edge-case seems totally pointless. A much more likely scenario is that your battery dies while you're out, in which case you're still screwed.

A better tried-and-tested real world solution that covers all scenarios is a simple key safe.

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I suggest this tiny thing named "key" is an appropriate solution. Hard to break through dropping, no battery, the home doesn't need electricity and so on.

While I understand the tinkering here for fun, the author did ignored the actual problem of the drained battery completely?

I shared this elsewhere but I could have expressed the initial problem a little clearer, which actually was "enter my home without unlocking my phone which causes my phone to die in the cold."

Unlocking the screen caused the battery to drop immediately - it still had network connectivity prior to that.

I think the initial problem was clearly-enough stated, and the GP's point is valid - why bother accounting for the case where your phone is so close to dying that you can't unlock the screen, when just a bit less battery life would mean that your phone dies regardless (and you're stuck outside anyways)?

The battery level isn't actually close to dying, in my case it just rapidly depletes from up to 40% when it's very cold. But that 40% remains intact seemingly with the screen off. Could be my phone also, but it has happened often enough that I wanted to solve it and thought this was an interesting approach.

For me, this was just a matter of convenience and not optimizing for most resilient or reliable solution. I do have backup plans for home entry.

I experienced this. I ran to work at -10F. When I arrived, I took out my phone to take a photo of my ice beard and although it almost immediately died.

Batteries are generally less able to source current when very cold. At low temperatures, the battery was sufficient to power your phone in a low-draw state (minimal network activity, no screen, low power CPU state), but the voltage dropped when current draw increased.

I had no idea this was a thing. How cold are we talking for this to be something that happens often?

It is more common than you think. Turing on the screen in cold weather is usually the thing to make the phone shut off. The solution still saves you the trouble of having to take off your gloves to access your phone.

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