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Comment by ggreer | Hacker News Reader

Like most PC manufacturers, Lenovo's exaggerates battery life claims. 15 hours is basically if you're idling the machine at minimum brightness with bluetooth and wifi disabled.

For example: Lenovo claims that my 7th gen X1 Carbon has "up to 18.3 hours" of battery life. Typically my laptop uses 5-10 watts. It can go as low as 2.5 watts if I dim the screen to its lowest setting, close all applications, and disable the radios. The battery is 52 watt-hours, so that would be 20 hours of "usage" before it runs out of juice. Really though, I get 5-12 hours depending on what I'm doing.

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This is one of the many reasons I keep buying Apple laptops. Their stated battery life claims are usually pretty close or at least reasonable enough. Then I hear all these types of things about PC manufacturers are it just makes paying more for a MacBook a little less frustrating.

Luckily, there are usually third party reviews with accurate battery life claims, at least for more popular laptops (like any ThinkPad). You're right that Apple does do a good job of accurately advertising battery life. On the other hand, since thermals aren't great on most MacBooks, some of Apple's performance statistics are only accurate for the first few minutes until the processor starts to thermal throttle.

how long does it last while asleep? i can close my macbook and come back to it days later and she always boots right up. just curious if the thinkpads are similar

Macs will suspend to RAM and write the RAM state to disk, then use the RTC to wake up 1-3 hours later and power off the RAM to save battery.[1] Resuming from disk takes 5-10 seconds while resuming from RAM takes a second, which is why OSes don't just suspend to disk.

The generic name for this behavior is "hybrid sleep" or "hybrid suspend". It's when the laptop does everything it needs to hibernate (suspend to disk), but then just suspends to RAM.

Almost every laptop is capable of this. The limiting factor is software support. You have to deal with different hardware RTCs, different disk encryption setups, swap partitions vs swap files (and how big they are). It's complicated enough that I decided it wasn't worth configuring, so my laptop loses 3-4% of battery life overnight. That said it is possible on Linux, especially if you use a swap partition instead of a swap file in an encrypted disk.

1. https://support.apple.com/en-us/HT202124

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