iPhone Battery, Again

In my previous post back in November last year, we started discussion of iPhone battery. My first iPhone was a 3Gs. Upgraded to iPhone 5 and then iPhone 6. For each I owned, the battery usually became less reliable after one and a half year of use. It was not uncommon to see battery suddenly drop from 20% to 8% or the phone simply shutdown at the end of year two.

The figure below shows the health status of my iPhone 6 battery at then end of its second year. I got 487 full cycles of charge and discharge. That's about one complete cycle every 1.5 days on average. The design capacity dropped to 73.8%. No wonder I felt the need to charge more often.

*Health status of iPhone 6 battery: the original after two years of service (left);
and the replacement battery (right)*

The Replacement Battery

I decided to get a replacement battery from Alibaba. There were many choices from no-name vendors to bigger names such as Sculd Battery Co.. Incidentally I bumped into a shop that claimed to sell authentic battery for iPhone 6 (see the picture below) and that's what I ended up buying.

The shop described in detail that the battery was authentic and carried three important features. I checked and can't see difference between the replacement and the original taken out of my phone (except the serial number). They are:

  • serial number built inside the battery chip (can be read by PC software)
  • silk-screen print on the battery pack
  • brand new connector (and its way of attaching to the pack)

The battery was manufactured on July 2014 by Desay Battery Co. (two months earlier than my original)! Desay is indeed one of the two authentic battery suppliers to iPhone 6. The other is Simplo Technology Co.. The shop actually had both in stock. I picked Desay for better quality I heard from online forums. If the date of manufacture is true, the shop must have stored the battery in fridge for the past two years! Indeed Lithium-ion batteries can be stored for long time without loss of design capacity in cool temperature and with 50% charged.

iPhone 6 replacement battery

The replacement battery. Right click to open in a new tab for full size.

Five months into service

The battery has a good run of five months in my iPhone 6. It came with a design capacity of 1824 mAh, better than 1810 mAh specification. The design capacity drops with use as the cell develops wear and tear internally. I decided to track such changes.

I use coconutBattery to take a snapshot of the battery's health whenever I charge my phone with a Mac. I probably should automate this task. Unfortunately not yet and so sometimes I'm lazy and might skip. The chart below shows the change of design capacity and cycle count at roughly two-week interval for the past five months.

The data upsets me a bit. Merely after five months, the design capacity loses as much as 10%. As a comparison, some people claim their batteries retain more than 90% design capacity after two years of use. Next I've accumulated 60 full cycles of discharge and charge so far. That's about 2.5 days per full cycle. Not bad, in fact much better than 1.5 days per full cycle of my original battery. I know the battery is new and may explain why it requires charge less often. We'll see.

*Change in design capacity (left y-axis) and cycle count (right y-axis) for the past five months*
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