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<blockquote data-quote="MacInWin" data-source="post: 1933023" data-attributes="member: 396914"><p>Sorry, but that is illogical. </p><p></p><p>LIthiium batteries decline for basically three reasons:</p><p></p><p>1. Time -- They ALL start to decay as soon as they are manufactured. It's slow, but eventually just time will kill them. Note that it is NOT the day they are put into service, it is the date of manufacture. </p><p></p><p>2. Cycles -- A lithium battery has a finite number of "cycles" in it. A "cycle" is defined as going from fully charted to fully discharged and back to fully charged. It's not necessarily linear, but most folks equate that with partial discharges, so going from 100% to 50% and back to 100% is "half cycle." That's not scientifically accurate, but it's generally ok. The number of cycles is not really fixed, and two identical batteries may differ on the number of cycles before the max capacity starts to decline sharply. And the batteries that Apple uses should outlast the "average" user's use of the machine, although folks who keep old hardware around far beyond when Apple says they are "vintage" will start to see battery issues. </p><p></p><p>3. Deep discharges and/or overcharging -- The chemistry in the battery doesn't perform well if the battery is either deeply discharged ( < 10% ) or over-charged. To avoid the latter, most batteries have a "reserve" capacity that is not available to the user as the battery reports "full" before it gets to truly 100% charged. Cheap chargers have ignored the "full" signal in the past and continued to charge batteries past the warning, which is why I don't buy or use cheap chargers. Apple's power supply and circuits in the MBP and MBA (as well as iDevices) are designed to maximize the battery life by NOT forcing the battery to true 100%. On the Discharge end, the chemistry is such that the charge from <10% to 40% or so is harmful to the chemistry. If you want to maximize the time your battery will be at close to max capacity, keep the battery between 40 and 80%, only going to 100% or below 40% when absolutely necessary.</p><p></p><p>As for why your post is illogical, If you assume that a battery has, let's say, 365 "cycles" (Most have many, many more than that, in the thousands, but I want to make a quick point) and you take it deeply discharge once a day, you will get roughly a year's service before the battery starts to roll off charge capacity pretty badly. But if you take that same battery and "cycle" it from 100% to 50% and then back to 100% each day, you use roughly a half-cycle a day, which means the battery would go two years before the same "cycle" count, lengthening the battery "life" overall. Even better cycle that same battery from 80% to 40% and then put it back on the charger to get back to 80% or so and the battery max charge will stay close to max for a very long time. It is not how many times it goes on the charger that shortens the battery life, it's how much of the capacity has to be returned to the battery on each charge. </p><p></p><p>Do some reading here: <a href="https://batteryuniversity.com/articles" target="_blank">Learn About Batteries</a></p><p></p><p>Those folks make and service batteries and have an extensive series of articles explaining how all kinds of batteries work and should be maintained. </p><p></p><p>In "real world" usage, the batteries and power supplies from Apple are designed to maximize the life of the battery, even to the point where, as I said, if I leave my MBP on mains power the battery is eventually lowered to 80% charge and held there to maximize the overall battery life.</p></blockquote><p></p>
[QUOTE="MacInWin, post: 1933023, member: 396914"] Sorry, but that is illogical. LIthiium batteries decline for basically three reasons: 1. Time -- They ALL start to decay as soon as they are manufactured. It's slow, but eventually just time will kill them. Note that it is NOT the day they are put into service, it is the date of manufacture. 2. Cycles -- A lithium battery has a finite number of "cycles" in it. A "cycle" is defined as going from fully charted to fully discharged and back to fully charged. It's not necessarily linear, but most folks equate that with partial discharges, so going from 100% to 50% and back to 100% is "half cycle." That's not scientifically accurate, but it's generally ok. The number of cycles is not really fixed, and two identical batteries may differ on the number of cycles before the max capacity starts to decline sharply. And the batteries that Apple uses should outlast the "average" user's use of the machine, although folks who keep old hardware around far beyond when Apple says they are "vintage" will start to see battery issues. 3. Deep discharges and/or overcharging -- The chemistry in the battery doesn't perform well if the battery is either deeply discharged ( < 10% ) or over-charged. To avoid the latter, most batteries have a "reserve" capacity that is not available to the user as the battery reports "full" before it gets to truly 100% charged. Cheap chargers have ignored the "full" signal in the past and continued to charge batteries past the warning, which is why I don't buy or use cheap chargers. Apple's power supply and circuits in the MBP and MBA (as well as iDevices) are designed to maximize the battery life by NOT forcing the battery to true 100%. On the Discharge end, the chemistry is such that the charge from <10% to 40% or so is harmful to the chemistry. If you want to maximize the time your battery will be at close to max capacity, keep the battery between 40 and 80%, only going to 100% or below 40% when absolutely necessary. As for why your post is illogical, If you assume that a battery has, let's say, 365 "cycles" (Most have many, many more than that, in the thousands, but I want to make a quick point) and you take it deeply discharge once a day, you will get roughly a year's service before the battery starts to roll off charge capacity pretty badly. But if you take that same battery and "cycle" it from 100% to 50% and then back to 100% each day, you use roughly a half-cycle a day, which means the battery would go two years before the same "cycle" count, lengthening the battery "life" overall. Even better cycle that same battery from 80% to 40% and then put it back on the charger to get back to 80% or so and the battery max charge will stay close to max for a very long time. It is not how many times it goes on the charger that shortens the battery life, it's how much of the capacity has to be returned to the battery on each charge. Do some reading here: [URL="https://batteryuniversity.com/articles"]Learn About Batteries[/URL] Those folks make and service batteries and have an extensive series of articles explaining how all kinds of batteries work and should be maintained. In "real world" usage, the batteries and power supplies from Apple are designed to maximize the life of the battery, even to the point where, as I said, if I leave my MBP on mains power the battery is eventually lowered to 80% charge and held there to maximize the overall battery life. [/QUOTE]
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