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Comment by paulannesley | Hacker News Reader

> For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month.

— https://web.archive.org/web/20110521104819/http://www.apple.... via http://apple.stackexchange.com/a/12280

This could also be useful, but doesn't answer the question directly: http://www.apple.com/batteries/maximizing-performance/

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The fact that Apple no longer has this statements on their website makes me think it's no longer true for their batteries (if it ever was).

They do have some advice on "long-term" storage here, which is roughly along those lines:

https://www.apple.com/batteries/maximizing-performance/

They don't say what "long-term" is, but monthly seems reasonable to me.

It specifically calls out recharging it to 50% every six months, so I assume it's a month+ kind of long term.

Also Apple seems to indicate that storage in a deep discharge state is far more damaging than storage at near-capacity based on the wording.

So if you're in doubt, charge it before you store it.

Finally, I don't think there's anything on that page that says you shouldn't keep your laptop plugged in when it's at 100%. I would be very surprised if they didn't have some cycle-conditioning going on. I have both a 2008 unibody and 2010 MBP, both essentially remaining plugged in for years. I don't think the battery life is abnormally low for their age, they still are capable of several hours of usage on battery.

Indeed. From my understanding, while this is still technically true, they have replaced the need for users to do anything with chips in the batteries themselves which shut off recharging when they're near 100%.

That's why if you pay attention you'll often see your battery % go from 97%-100% and then back down to 97%. It is reporting as "charging" but in reality it goes idle to let the battery de-charge a little.

Or they're trying to bolster sales of their warranty initative: Apple Care

Usually the reason behind discharging fully once per month is because when this happens, the laptop records how much capacity is required to recharge the battery. This will keep your battery % left accurate.

The actual preference for getting the MOST DISCHARGES out of a lithium ion battery is discharging it to 50%. This, however, doesn't not to equate to longest battery life (in terms of age) for the use within a laptop/phone.

Edit: There is something state of charge estimation models which may rely on this variable to decide how full they'll charge the battery. If you don't fully discharge and fully recharge the battery to update this capacity value, the SOC estimation model might overcharge the battery, thus decreasing the lifespan.

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