The correct way to use your MacBook's battery  

Posted by dhamotharan in ,

Recently a battery completely failed in a two-year old black 2.16GHz MacBook that was covered under AppleCare. It worked fine one day, went completely dead the next. It wouldn’t charge and no LEDs would light up. When I brought it into the genius bar at my local Apple Store I learned something interesting about the way Apple treats batteries covered under warranty.

The first thing that the tech did was run a diagnostic application on the battery from a bootable iPod nano (pictured). The application graphed the gradual decay of the battery over time and the little black dot could fall into one of two buckets: defective or consumed (not the exact terms, but you get the idea). Luckily, the little black dot on my battery fell into the defective area and was replaced.

Since batteries are consumable parts (like tires on a car) Apple doesn’t cover them indefinitely — even if the machine is covered under its AppleCare Protection Plan (APP). Batteries that areconsumed are considered past their normal lifespan and will not be replaced under warranty.

One of the telling things about this particular visit to the Apple Store was something the tech told me. He said that he would replace the battery with a new one because it has be “used correctly.” When I asked him to elaborate on what that meant, he told me that Apple’s notebook batteries last longest when they’re routinely charged and discharged.

My defective battery had 200+ discharge cycles on it which means that it had be charged and discharged that many times — in Apple’s eyes more is better. He wouldn’t give me a specific cutoff point but he said that when a customers comes in with sub-70 charge cycles over 2+ years they know that it’s probably been plugged into AC power most of the time — which is not how the battery is designed to work and can lead to premature failure.

He went on to say that the chemistry inside a rechargeable battery works best when it’s used — translation: charged and discharged — and that if it’s always plugged into AC power (and fully topped off) most of the battery isn’t being used and will gradually decay. The genius helping me claimed to have 700+ charge cycles on his three-year-old battery and said that it still gets three plus hours of run time as as result.

I guess the lesson here is to unplug your MacBook and let the battery run down before recharging it.

Quick poll: Post the age and number of charge cycles on your MacBook battery in the TalkBack. (You can check the number of charge cycles in System Profiler > Power > Battery > Health Information > Cycle Count.)

This entry was posted on 7/2/09 at 8:25 PM and is filed under , . You can follow any responses to this entry through the comments feed .

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