Earlier today I went to recharge my Mini for a few hours. Upon coming back to it, the unit will not power on unless the USB cable is attached to a power supply. Even then, it only displays a picture of a half-full battery and a “Low Battery” message. I have attempted to contact Support via the Contact form a short while ago but I wanted to post about it in case anyone else has experienced a similar issue and has a solution.
Thank you,
Erik
Uh oh! 
This is a first (have not heard this before).
I’m guessing / hoping this is either a faulty battery or a cable has come loose.
While this sucks, the good news is, this should be a relatively easy fix (if it’s one of these two) but probably best to wait for Polyend Support, before you go opening up your Mini.
From what i know (and Polyend has shared here), the battery should be a Nintendo Switch Style Battery and should be user replaceable… again if that’s the problem of course.
Since it’s the weekend you might have to wait till next week for an answer though.
Keep us informed and best of luck 
From further discussions we’ve had on Discord - perhaps this is valuable as well. When connected, your unit seems to show something to the extent of “Charging…”
Mine does not. It only briefly displays a 50% charged battery and the words “Low Battery.”
After some further discussion I decided to open my Tracker Mini and see if I could resolve the issue.
Using a Torx T3 screwdriver and some Spudging tools, I was able to open the unit and found that the battery connector - while it looked connected, clearly was not providing power to the unit. After sliding the connector back on the unit has worked fine.
I’m somewhat concerned that light use caused this issue, though. I’ve only been taking it on walks and tossed it about while in it’s hard-shell case. I might end up opening the back again and using some adhesive to make the connection a bit stronger.