Once the two halves of the housing are split everything is pretty accessible. The two halves will still be connected by the flex cable assembly that runs from the primary logic board to the charging pins and LED Indicator, but there is quite a bit of slack in it and the top half clears the lip easily.

The battery itself is marked as "Model GYJS0, Rated Capacity 500mAh 1.85Wh, Rated Voltage 3.7VDC" and searching the Google Product Support website for more information also tells us that when this cell was tested to make sure it complied with UN 38.3 standards the cell itself weighed in at 10g https://support.google.com/product-docum...