Battery wearing out?

anon(10181084)

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Mar 2, 2017
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My Tab S3 has been serving me well (and even better with the official build of Pie I use) for almost two and a half years now. But weird things started happening. I like connecting all sorts of stuff via a USB-C dongle (frenzy with this started earlier this week) and I noticed that sometimes if the setup is drawing a large amount of power (causing battery current to hit 4 amps), the tablet shuts down and then refuses to start until I briefly plug in a charger. And then, ever since I added cheap Chinese PS/2 to USB converter for a PS/2 mouse (yes, I use a PS/2 mouse with my tablet), the tablet refuses to charge at an acceptable speed after 80%. This is how it has behaved the last two times I charged it from below 10% (I occasionally deep discharge this much, although I did empty or near empty almost every time until several months ago before I heard frequent deep discharge is bad). Until 80% it charges very quickly (using QC port on my charging station). At 81% it throttles the charge speed down to around 396mA and by 87% (and HOUR plus after 80%) is is down to 58mA.

There is no indication in my testing that I am overloading the USB-C port, and my dongle's protection cuts out the USB output at a sensible current (1A on tab s3 and 1.2A on my S8) and immediately returns power when excessive current is removed, and I never ever get the classic high power USB device warning that plagues some other dongle users.
Also, if the current draw on the USB-C dongle outputs is over 750mA or so for a prolonged time while I am heavily using the tablet, it also experiences the above mention shutdown.

I think my battery (233 cycles shown in DevCheck, 5582mAh according to accubattery) might have elevated internal resistance or something. I remember being able earlier this year to power an old 2 amp tablet from the USB-C with an OTG plug and it happily worked and the Tab S3 didn't crap out and require a jumpstart. My S8 handles full blast USB usage (and a little over 4 amps battery current) without shutting off or having any charge issue triggered in a quick 2 minute test, but my S8 is only a few months old and has half the number of charge cycles as my Tab S3. And I honestly don't know why this charging issue got triggered right when I introduced the adapter cable for the mouse. Another thing of note is that the ethernet on the dongle mysteriously got messed up and doesn't work no matter what device I use it on, but I am not sure that has anything to do with this.

I'm not sure if this is a battery issue or just me being an overzealously crazed dongle user...