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Comment by flotzam | Hacker News Reader

FWIW, "It won't be supported by GrapheneOS. (...) Bluetooth still has to be configured and enabled by the OS to make it work that way."

https://discuss.grapheneos.org/d/11520-android-find-my-devic...

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The article linked there has a few more details about the implementation:

https://www.androidpolice.com/android-15-powered-off-finding...:

> To solve this problem, Google is working on a “Powered Off Finding” feature that allows a device to store precomputed Bluetooth beacons in the memory of the Bluetooth controller. This means that even when a device is powered off, it can continue broadcasting Bluetooth beacons to nearby devices.

> Unfortunately, Powered Off Finding isn’t the kind of feature that can just be enabled on any device. This is because the device needs to have hardware support for powering the Bluetooth controller when the rest of the components are shut down. Plus, device makers need to put in some extra engineering work to support this feature. For example, they need to support the Bluetooth Finder hardware abstraction layer (HAL) so that the Android OS can enable Powered Off Finding mode and send those precomputed Bluetooth beacons that I mentioned.

I don't know how that could work if the battery is dead, unless they're letting the Bluetooth controller draw on some reserve battery capacity after the phone has powered itself down.

There is mostly dead and then there is all dead. A battery which is unable to supply enough power to keep the entire phone operating can likely supply enough for just the Bluetooth chip. Of course, the resulting deep discharge may damage the battery chemistry.

I'm pretty sure phones shut down long before they reach 0%, keeping plenty of charge for the Bluetooth beacon. The battery protection circuit will for sure prevent deep discharging by cutting the power.

We've discovered the mythical "unlimited". Unlimited Bluetooth power :-)

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