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Summary:

What’s the best way to extend the service life of your notebook battery? Not runtime between charges, but how many charges you can get from a Lithium Ion battery before it will not longer hold a useful charge. Ivan at CreativeBits has posted a tips column […]

What’s the best way to extend the service life of your notebook battery? Not runtime between charges, but how many charges you can get from a Lithium Ion battery before it will not longer hold a useful charge.

Ivan at CreativeBits has posted a tips column noting that typically notebook computers are used as desktop substitute machines plugged into AC power adapters most of the time, which is problematical. Ivan suggests that batteries “wear off much more faster (sic) if they are not being used enough.”

Is that an accurate evaluation? I think not.

Lithium Ion Batteries — The Clock is Ticking

Lithium Ion batteries can handle a finite, somewhat variable number of charge cycles within a loosely defined lifespan of two to three years. The clock starts at the time of manufacturing, so stocking up on spare batteries isn’t a good idea, nor is discharging and recharging them frequently when not necessary for untethered computing, which will shorten service life dramatically.

According to Apple’s Knowledge Base, “You can charge all lithium-ion batteries a large but finite number of times, as defined by charge cycle”… “Using and recharging 100% of battery capacity equals one full charge cycle.”

Apple says a charge cycle means using all of the battery’s power. For example, if you partially discharge your battery one day, using half its power, then recharge it fully, then do the same thing the next day, that would cumulatively count as one charge cycle, not two.

Battery expert Isidor Buchmann says a lithium-ion battery provides 300 to 500 discharge/charge cycles and prefers partial discharges with a periodic, deliberate full discharge and recharge every 30 cycles or so to keep the battery properly calibrated. Wikipedia’s entry on the topic concurs, recommending that lithium ion batteries should be charged early and often, and should not be frequently fully discharged and recharged.

Storage Conditions a Factor

Environmental temperature also affects battery life. Cool environments are best, and the torrid temperatures inside today’s laptops are less than ideal, to say the least. For maximum longevity, a widely-recommended procedure is to keep the battery at about 40-80 percent charge, removed from the computer, and stored in a cool spot when it’s not needed to power the machine or if the computer will be dormant for some time. For example, schools that don’t use their laptops over the summer should charge the batteries, remove them from computers, and store them in a cool location.

While cool storage is ideal, it may be best not to store laptop batteries in the refrigerator as is recommended by some authorities. A reader reports trying this and ruined a battery due to moisture damage from condensation.

Real World Needs Conflict With Battery Life Optimization?

Isador Buchmann advises not leaving the battery in the computer with the AC adapter plugged in unless you’re actually charging it, and storing it in a cool place at about a 40 percent charge, maintaining that the most harmful combination is full charge at high temperature.

However, one of the reasons I’m a laptop fan and user is to avoid data loss when there’s a power outage and to be able to keep on computing during blackouts. For those purposes the battery needs to be in the computer and fully charged.

I keep my laptops plugged in with the battery aboard. That may not not ideal strategy for optimum battery life, but it has worked reasonably well for me for 12 years. Original batteries in my PowerBook 5300 and G3 WallStreet lasted more than seven years, although my Pismo PowerBook’s OEM battery barely made it to three (I bought that computer used, and the previous owner had run many charge cycles). The OEM batteries are still in my G3 iBook (December, 2002), and 17″ PowerBook G4 (manufactured sometime between September 2003 and April 2004 — Apple Certified Refurbished in July 2005).

The bottom line here I guess is that if you took the trouble to always remove the battery while running under AC power, you would extend its life, but doing so obviates some of a laptop’s marquee advantages — data security, uninterrupted computing during power outages, and quick getaways.

The most comprehensive online resource on battery care and maintenance I’ve found is “Batteries in a Portable World” also by Isidor Buchmann, which is book length and contains a ton of useful information on batteries.

Have you found any methods that you think have extended your battery life? Any other tips/tricks you know of for getting the most of each charge?

  1. “The OEM batteries are still in my G3 iBook (December, 1992),” Did you mean to say 2002? 16 yeas is an awfully long time for a battery. And the G3 came out in 1997, right?

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  2. I’ve heard stories that the power supply in a notebook actually expects the battery to be in the unit when it is in use. Removing the battery may be a good idea to keep it in optimal shape, but it may be bad for the notebook itself because the line power is less buffered than it should be.

    I would love to hear the ideas of an expert on that subject.

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  3. Interesting how things have changed in two years.

    These days it really seems to be a crap shoot on battery life. Kind of like the US Economy, it seems like the technology is too variable for an accurate idea of how long to expect batteries to last.

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  4. Hi Sam;

    Arrgh! 2002 it definitely is.

    1992 was the year I bought my forst Mac – a compact Plus.

    Thanks for the heads-up.

    Hi Rob;

    Good question. Not one I’m equipped to answer with any technical authority, but I do recollect that during Apple battery recalls they have recommended removing the battery and running on AC power, and I don;t think they would make such a recommendation if there was risk of damaging anything.

    I found a couple of forums dicussinf this topic, but nothing definitive.
    http://forums.macrumors.com/showthread.php?t=71689
    http://harry.sufehmi.com/archives/2007-03-03-1425/

    Charles

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  5. All this talk is kinda fluffy, especially considering how often we Mac users are upgrading. I don’t see my AC usage killing my MacBook Air battery before I move onto new technology.

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  6. Devin: Also, with third parties still making high-capacity batteries for iBooks and PowerBooks, it’s not like you won’t ever be able to replace one. And the new battery is likely to last longer than the old one did initially.

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  7. Don’t forget that Intel said that removing the battery makes the CPU go slower. On the first MacBook Pro, when you removed the battery and left the AC, the CPU was running at 1Ghz !
    So yes it is a good idea to remove it when plugged but only if you don’t need full power.

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  8. i confirm that also occurs with 15″ MacBook Pro 2,4 Santa Rosa, BillyGuy. Removing the battery slows down performance.

    And I must add my experience with a 62% Health battery after only 70 cycles!!! Got replaced and the second one is starting to fail… :-(

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  9. taking good care of my battery to gain a couple of months of use is not cost effective at all.

    in one laptop lifetime (about 3 years) i go through about 2 batteries with about 400-500 charge cycles each.

    not extending the battery life by about 10% over the course of 15 months costs me $25 tops, that is $50 for three years.
    that adds less than 3% to the total cost of ownership of, let’s say, $1500 for a macbook.

    that is a price i gladly pay for not bothering with any battery-hand-holding.

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