I have a 15″ MacBook Pro with Retina Display (Late-2013) and it is approaching 5 years since it was manufactured. It is still going strong but today I replaced the battery as it was becoming swollen and potentially unsafe to use.

I’ve been running the following simple script on my MacBook for most of its life which records battery info taken directly from the battery hardware:

datetime=$(date)
batt=$(/usr/sbin/ioreg -l | grep -i "capacity")
echo "$datetime" >> /test.txt
echo "**" >> /test.txt
echo "$batt" >> /test.txt
echo "**" >> /test.txt

After parsing the data and sending it to IoTPlotter.com I could view the degradation of the battery over time. Here’s an image of two graphs generated from the data:

Graphs showing battery cycles and health
Tip: Click the image to enlarge for better viewing

The large numbers above the graphs on the right is the current value from the new battery; I excluded the new battery from the graphs.

There’s two noteworthy points on the graph. Point A (24th October 2013 – 8th November 2013) is the period of time where I owned the MacBook but hadn’t created the script. Point B (27th January 2016 – 6th July 2016) is a period of time where the MacBook was out of my possession; I’m not sure how much it was used during that period but it accumulated 2 cycles at some point within that timeframe.

`Cycles` refers to the number of battery charge cycles, and `health` is the battery ‘Maximum Capacity’ divided by the ‘Design Capacity’ and multiplied by 100 to get a percentage. This is a common metric reported by various 3rd party MacOS applications; it essentially shows how much energy the battery can hold compared to Apple’s initial design.

Interestingly, the battery health didn’t consistently drop below 100% until after 2015; approximately 14 months after I started using the MacBook and after 100 charge cycles or so.

I also find it interesting that my MacBook was manufactured on week 43 of 2013 (21st – 27th October) according to appleserialnumberinfo.com and this MacBook was only announced on 22nd October so either Apple started production at the same time as the announcement or I just happened to get one of the batches which was produced that week. Either way, the age of the battery at the time of replacement was 260 weeks.

I purchased the replacement battery from the iFixit EU store and System Information reports the device name as `bq20z451` made by SMP. The battery health is currently 104.57% with 0 cycles. I’ll continue running the script so once I stop using this battery/MacBook I’ll be able to make a comparison with the original battery.

Here’s an image which I took today during the battery removal which shows the swollen batteries and 2 removed cells:

Inside a MacBook Pro with 2 battery cells removed

The battery hadn’t swollen enough to cause any serious problems, however the trackpad had noticeably less travel while clicking and for a short period this year 3 keys on the keyboard were sporadically failing to work – The keyboard issue stopped about 2 months ago so may have been unrelated to the battery but the trackpad was back to normal immediately after I replaced the battery.

Categories: Hardware

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