How to prolong your MacBook's battery life

Q. My MacBook Air now shows a “Service Battery” warning under the battery-gauge menu. Can I ignore it, or is the battery about to die on me?

A. If you use one of Apple’s laptops for enough years, you will probably see this message when you click on the battery icon at the right end of the menu bar.

Apple’s help-file documentation is a study in vagueness: “The battery isn’t functioning normally, and you may or may not notice a change in its behavior or the amount of charge it holds.”

Fortunately, that note adds that you won’t hurt your Mac if you ignore this advice to get the laptop battery serviced: “You can continue to use your battery before it’s checked without harming your computer.”

An independent expert in Mac repair agreed, saying the only real risk is decreasing battery life.

“You can ignore it, but I find that once it gets to that point, your computer will start shutting off before the battery gets down to 0%,” said iFixit founder Kyle Wiens. “The battery probably doesn’t last nearly as long as it used to.”

That’s a consequence of the battery going through too many charge cycles, meaning the times you use up all the electricity stored in it. Lithium-ion batteries like thoseApple uses in its laptops start to lose capacity after reaching that limit, which on most MacBook models is 1,000 cycles.

You can see exactly how far down this road your MacBook battery has traveled by checking Apple’s System Information app. Click on the Apple icon at the top left of the screen, select “About This Mac,” and then click the “System Report...” button.

Now click “Power” in the index of hardware categories on the left side of that window. You’ll get a long page of details, the important one being the “Cycle Count” listed under “Health Information.”

On my own MacBook Air, which began showing that “Service Battery” message two weeks ago, the cycle count now stands at 753 of the advertised 1,000. That’s less than I would have expected for a machine that’s seen heavy use since 2012.

(I might have replaced this MacBook already if Apple hadn’t let its laptop lineup get so stale. I can’t get too enthusiastic about paying this year’s prices for last year’s hardware.)

You can have Apple replace the battery at one of its stores or send it in for the service. Apple charges from $129 to $199 for this service, depending on the model. Or you can try to do this yourself--Wiens’ iFixit site offers detailed instructions and sells tools for the task.

Going the DIY route for my MacBook Air is tempting, but when buying iFixit’s suggested battery alone costs $110 and Apple will do the whole procedure for $129, I’d just as soon let somebody else crack open the laptop.

Which can now apparently wait a little longer: After I installed Apple’s macOS Sierraon my laptop, the “Service Battery” message now longer appears, and the system reports the battery’s condition as “Normal.”