Replacing a MacBook Pro Battery

It was a perfect late winter day outside - abnormally sunny and warm. I decided that rather than spend it in my office I’d grab my MacBook Pro and take it out on our deck, feel that nice breeze and work through some code. I got comfortable, flipped it open and started to plug away in Xcode. Everything was ideal - so much so that I’m sure photographs of me sitting there would have made for great stock photography for some web site.

After about 15 minutes of moderate use I looked at the status bar and noticed that my battery was already down to 79% available. This was not good. 30 minutes in, I was down to 50%. iStat menu was trying to predict how much longer I had and the number of minutes of power left were dropping like some kind of warped time traveling machine.

I went from Carpe Diem to Carpe Power Cordus. Total buzz kill.

I’ve now had my MacBook Pro for nearly three years. This particular MacBook Pro is the last generation before the unibody models debuted and as such has a replaceable battery. A little over a year ago my battery started acting up something fierce and Apple was kind enough to replace it, though technically it was out of warranty.

They did this because my number of cycles were so low (47) and it was clearly in need of replacement—the Apple store ran a test on it that said “Battery BAD”. They issued me a brand new battery and sure enough, I was able to get a few hours (2-3) out of it on a full charge. I made a commitment to myself to cycle the battery frequently but that only lasted about a month before I fell into my old habit of just leaving the machine running 24x7 and connected to power all the time. I did cycle the battery down at a minimum every month, but not every single week.

Apple insists that the best way to extend the life of the batteries in a MacBook Pro—at least for my generation MacBook Pro—is to regularly run it off batteries. This would “keep the juices flowing” within the cells and ensure they last longer. This seemed a little self-serving because they use the cycle count (recharge cycles) to determine how old a battery was. If I did as my Apple Genius recommended and cycled my battery constantly I’d have 350+ cycles in less than a year pretty easily. The old Apple page for my MacBook Pro suggested that after 300 cycles my battery should still have 80% of it’s charging capacity. The new unibody models are apparently much more efficient and are designed to get to 1000 cycles before dropping to 80% capacity.

So here I was with a battery a little over a year old, it had a grand total of 54 cycles on it and was down to 79% health. I tried the Apple recommended reset procedure but it had no impact. Rather than going back to Apple I decided to try a different route.

NewerTech NuPower Battery
I did some research and heard good things about the NuPower Batteries so I decided to buy one through Other World Computing. It was $30 cheaper than the Apple battery so I figured it may be worth a try.

The NuPower Battery that arrived was virtually identical to my existing Apple battery. Everything, right down to the status indicator was identical. It fit into my MacBook Pro perfectly and I followed the instructions to get the battery calibrated.

Once calibrated, my MacBook Pro’s battery performance was right back to brand new levels. I’ve had this battery installed for 4 weeks now and it’s performed perfectly, giving me a solid 3-4 hours of “battery time” based on how hard I push my MacBook Pro.

One interesting aspect of this NuPower battery is what iStat Menu reports in terms of Design Capacity and Current Capacity. After a couple of full cycles and 4 weeks of use, the battery reports a design capacity of 5400 mAh, but a current capacity of 5607 mAh. However my older Apple battery had a design capacity of 5600 mAh but had been reduced to 4442 mAh. I’m not sure why the internal indicator on the NuPower is only displaying 5400 mAh capacity but clearly it’s exceeding even the design capacity of the Apple battery in actual usage.

Some Tips For Making the Battery Last
I’ve read pretty extensively on Lithium-Ion battery technology and believe that Apple is giving good advice in telling you to rotate off power fairly regularly (at least monthly). What they don’t tell you is that if you do keep your MacBook plugged in most of the time that the heat of your machine running will also cause your batteries to deteriorate more quickly.

Battery University has some great pages on what can impact Lithium-Ion battery life and heat is as big a factor as anything for long-term battery performance. As a result I ran a few tests by using the Sensors gauge in iStat Menus and found that for my MacBook Pro the battery temperature ranged from 91F to 94F while my machine was open and running on plugged-in power. Normally I would leave my MacBook running 24 hours a day; I’d have the screen power down and the HDD spin down but even in those conditions the battery temp hovered in the 86F range.

However if I put my MacBook to sleep by closing the lid, the battery temperature immediately on waking up was registering as low as 75F after a few hours - the same temp as the room it was stored in. That 11F to 19F range is pretty substantial and something I think factored in to my battery’s early demise.

If you—like me—run your MacBook 24 hours a day not only should you run it off batteries every week or two to keep the battery juices circulating, you should close your machine’s lid when you walk away to let it cool down when not in use. You can of course set your Energy Saver preferences to put your machine to sleep after 10-15 minutes of non-use while on power as well. I personally have it set for 10 minutes, however if I know I’ll be away for a bit (lunch, going to bed, etc) I just close the lid. One of the better features of Macs is that they wake from sleep reliably and nearly instantly - best to take advantage of that.

Got a tip for making that battery last longer? Please drop a note in the comments!


Anonymous said…
I too have one of the last "removable" MBP 15" and have it hooked up all the time to an external monitor. After ruining a first battery with the power always hooked up, I now removed my battery when used in a "desktop" configuration. I feel this protect the battery for damage. Just have to watch I don't pull the plug, as computer has no battery backup anymore. **Side note: The newer laptops allow you to run and external monitor without the power cord plugged in (but who knows how this effects the build-in battery?)
David Alison said…
@R: If you read the above link to Battery University they recommend letting the battery drop into the 40-70% range if it will be without power for a while. May help preserve it a little longer.

Ironically after I wrote this blog post I had to travel with my MacBook Pro and pulled up iStat Menu to find that my recently charged battery now has a current capacity of 5698 mAh! After a month the battery appears to be getting a little stronger...?
brian said…
I have one of the non-removable battery MacBooks. iFixit shows how to replace even these. It's painfully simple. Can't imagine anyone looking at the site deciding to not to it themselves.
-I quit said…
This comment has been removed by the author.
bhoover said…
I'm in the market for a new battery, this will be my second in 5 years. Can you still recommend the NuPower battery over the Apple one? I hope so.
David Alison said…
Yep, great battery and highly recommended.
Anonymous said…
I bought a MacBook battery from them which only lasts 2 hours and reports 90% battery health. :( Wouldn't recommend.

Unknown said…
One thing's for sure: it's a lot easier to change macbook keyboard stickers than it is the battery itself. Macbook owners be warned - take care of your batteries or face the consequences.

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