I've found this thread today, after my SP5 battery worked just only for 2 hours today; then I've started to search for similar issues reported, reaching this scary thread.
I bought my SP5 early January 2018 and I thought when the battery fail (because all brands will fail sooner or later), at least, I could keep using my device plugged to the AC power supply, which seems it is not the case.
I have registered my device, as I presume all of us, with my Microsoft account and the have me email address and the serial number of my SP5.
As I am guessing this is a general issue, reported from USA to New Zealand, Asia and Europe my only two cents:
I was one of the Intel Pentium early adopter, which was affected by
https://en.wikipedia.org/wiki/Pentium_FDIV_bug
The Spanish computer reseller contacted me, even before I realized I had one of those Pentium, and the asked me to bring my PC to the store because Intel will replace for free my computer CPU.
On those days should be more difficult to locate the buggy CPUs, but Intel did.
As I mention before, Microsoft has my Surface serial number and Microsoft account among other device data with the telemetry we provide to them.
Let see how many days my device keeps working. Today my battery report says:
DESIGN CAPACITY
45.000 mWh
FULL CHARGE CAPACITY
23.570 mWh
CYCLE COUNT
248
Report generated AC 88 % 23.570 mWh