I have a MacBook Pro running Windows 7 x64 via Boot Camp. I recently lost work because, on receiving a low battery warning (at 10%), I closed the lid to put the laptop to sleep, but then forgot to plug it in. When I started the machine again, it displayed "Windows did not shut down successfully". It seems that the laptop ran out of battery power and transitioned directly: Sleep => Powered Off.

When the laptop is running, if the battery drops below critical (5%), it successfully transitions: Running => Hibernating. If the battery drops below 5% while sleeping, should it transition: Sleep => Hibernating?

If so, how can I find out why that did not happen?


Windows does not transition from Sleep => Hibernate when the battery drops below a certain level. Windows cannot do anything when it is not running, and there is no standardized ACPI feature to allow a computer to wake when the battery drops to an arbitrary level.

Windows does transition from Sleep => Hibernate on a timer, if such a timer is set when Windows goes to sleep - there is a wake on timer feature that Windows can use for this. Windows sets the wake timer when it goes to sleep, and if the power state is appropriate, transitions to hibernate when it is woken by the BIOS/EFI. There is no equivalent feature to wake-on-battery-level.

Some BIOS/EFI implementations have a manufacturer proprietary function to transition to hibernate when the battery drops below critical. By definition, these only exist on certain proprietary machines.

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