Ask HN: Could a phone at sub-zero (C), heated by load, result in net inc. usage?

[txmachinery]

Those who've spent time in a sufficiently cold environment (below zero C), and spent time outside with a fully-charged phone, may have experienced taking it out to snap a photo, only to have it suddenly register low-battery life, and then completely shutdown, sometimes within seconds. Mobile phone batteries at sub-zero temperatures lose voltage, and as a result can incorrectly think they have depleted the battery. If cold enough, they will shut down completely. Observing that the same phone, when under certain conditions of high load, can exhibit significant increases in overall temperature; could there be a net positive in terms of usable time, by intentionally ladening a sub-zero degree phone with redundant tasks, with the intention to create sufficiently distributed heat in the phone housing, and therefore warm the battery to the point it performs nominally, resulting in a net positive in terms of being able to use the phone for a longer time - or in extreme cases - at all?

[sigmaprimus]

If I understand what You are asking, I would say the built in heat management design of modern phones would make this ineffective as they intentionally sink heat away from the battery. This is why the phone feels warm under high use.

A more simple solution would be to keep a portable power bank (less than 30 dollars on Amzn)in your pocket and power your phone from it with a long usb cord.

If you dont mind the bulk and have a big enough pocket you can get one with a hand crank, flash light, bluetooth speaker and tuner. If space is an issue there are small ones available that can attach directly to the phone.

A power bank might be a good way to keep your phone warm too, you can pick up a peltier thermal module and usb adapter (less than 10 dollars on Amzn) and tape it to the back of your phone.

Just make sure you dont heat your phone up too much (+30C) as charging lithium cells above that temp will damage them.

[txmachinery → sigmaprimus]

Thank you. The power bank may work as a hardware solution sometimes, though even in a pocket, any battery can fail if the outside temps are low enough (as they often are in winter at higher latitudes).

I essentially was wondering if the heat a phone produces during higher-load operation might be repurposed to create an entirely software solution to the problem of a battery dropping below functional temperature. Your answer suggests it can. Perhaps this could also be balanced by some kind of dynamic heat-dispersion design to account for the converse issue of battery temperature getting too high. But that's encouraging - if modern designs intentionally direct heat away from the battery, that suggests the basic software-only idea might be possible in principle, and maybe in practice - in any existing phone that has poor hardware design in that respect. Components under load increasing battery temperature must be a valid effect, to necessitate designing around it - so using this "feature" to conversely keep battery temperature higher than its operating minimum may be a valid proposition.

Extreme cold situations can also sometimes be an emergency, so it's not necessarily a trivial issue. Granting phones a kind of rugged-cold mode to prevent shutdowns, via a software update that makes simple power management choices dependent on outside-temperatures (phone getting too cold: crunch numbers and activate display), could potentially save lives.

[sigmaprimus → txmachinery]

I guess you could test out your theory with a freezer and a stress test app.

Here is the top result of a simple google search, you can take it from here.

Good luck.

>>>> The description of Phone Stress Test Phone Stress Test places a high load on the CPU, memory, and storage of an Android Phone or Tablet. The Android device will draw more power from the battery and will run hotter while the tests are running. m.apkpure.com › Apps › Tools Phone Stress Test for Android - APK Download - APKPure.com

[txmachinery → sigmaprimus]

Ah, that's great. Thanks!