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Comment by dartdartdart | Hacker News Reader

For people who use their laptops primarily as plugged in machines, there should be a 50% max charge mode.

I keep my MacBook Pro 16" plugged in 80% of the time, but when I want to go work at a coffee shop on battery having 50% would be a big inconvenience. How much longer in terms of battery life are we talking doing 50% charge vs 100%?

You would remove the 50% charge limit prior to undocking so that it's at 100% right on time. Calendar integration could easily automate the limit-removal time (maybe 30min before you have to leave, or whatever is needed).

I think you are vastly underestimating my spontaneous and lazy nature.

Why is it not possible to completely save the battery when on AC? i.e. charge the battery to 100% (or something close) but power the laptop directly via the charger.

>i.e. charge the battery to 100% (or something close) but power the laptop directly via the charger.

That's already what's happening. However that's not enough. Leaving the battery full is harmful in and of itself.

Understood. So why hasn't Apple done something about this earlier? IOW, a setting that charges the battery to a maximum of 80% when plugged in?

Because you need to predict whether people want to use it plugged in or on a full charge afterwards.

Are you sure? I had read elsewhere that it always goes through the battery, and a sibling comment says there is insufficient power from the charger alone (not really sure how that's possible either though).

>power the laptop directly via the charger

Recent macbooks can't run directly from the charger. The charger is not beefy enough to provide power during peak CPU/GPU usage.

Why 50%?

the optimal charge state for long-term storage of a lipo cell is about 33%. 50% is a nice buffer on top of that if you use it unplugged for an hour or so, then put it away.

The use case here is plugged in and, presumably, using the laptop, not storing. Is 50% still the ideal charge state, in that case?

maybe not, but it's probably not much worse than the optimal charge state. you want to keep a lipo cell at 3.7v for optimal longevity. usually this corresponds to above 20% charge but below 80%, but the concept of "charge level" is sort of arbitrary. the manufacturer has already set safety buffers on either end of the spectrum, but the exact amount will vary based on risk tolerance, application, etc.

Manufacturers send products out at 60% so I assumed 50% would be the best if you're not expecting to lose charge over time

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