CoxBox Mini Battery Check

The dark Blue Cox Box Mini has battery issues

NK want $35x3=$105 for the batteries plus $77 to actually change them and I suspect anoth couple of $ in freight.

Decided to have a look

 Opened.
Measured the individual Cell Voltages. I measure from the Mic connector end.
All 3 were 3.8V when OFF.

when ON, I get -4.8   3.8  3.8
Then observe the LED is OFF so switched OFF and measure

-0.8  3.8 3.8

CELLS Are 50mm x 34mm x 4mm 

NEW BATTERY
Ordering from Core Electronics
https://core-electronics.com.au/polymer-lithium-ion-battery-1000mah-38458.html

Needed a TORX driver

I measured the batteries as
 50mm x 34mm x 4mm
But the 4 might be 6

It says
TUNTONG
YT523449 3.7V
930mAH  3.4WH
201507

CARE OF LIPO BATTERIES

This seems a good article

https://rogershobbycenter.com/lipoguide