Too all forum readers - a generic statement.
Mounting evidence from users whom replaced their battery points out to 100% resolution of the mysterious shutdown issue. As much as I sympathize with the sudden inconvenience of having to replace a battery, no words can express the strong discouragement I have towards 3d party fake-Apple batteries which flood the market out there.
- The may be 1/2 1/3 of the genuine OEM price but will not performs even close to the real hardware. No 3d party fake 'like Apple" or "OEM" dealer has access to the lowest price, which is Apple's 300 million units/year bulk.
- 3d party battery user reports include short life,overheating, inconsistent performance and, worse, iPhone fire
- Genuine OEM batteries come with special packages. An authorized retailer can show it to you (and you can always check with Apple).
- Part of his relationship with Apple, the authorized retailer sends your defective battery back to Apple. So that dead battery serves a final purpose, indexing and further evaluation to determine common denominator. That is how warranty recall cases are build. 3d party vendors, or users replacing their own batteries, do not.
Years ago I have myself done the 3d party battery thing. After discovering that the 3 year warrantied "better than Apple" batteries never lasted more than a few weeks, I found out that:
- They only lasted weeks to months at most
- I had to pay for return shipping
- I could not send them by plane (dangerous goods) and if I tried, own risk of non-delivery
- Recommenced the cycle with the replacement.
As for local vendors, such as in the town I am in, they are open as to showing their authorized status, and OEM parts packaging, replacement screens or battery.
Best Buy is another known Apple authorized battery replacement place.