Here is a quick answer and a few things I found out so far. Sorry I have to post this as an answer but I do not know how to attach images to comments. this is from here Camera. Seventy times a second, the pen photographs specially printed paper within a radius of seven millimeters, using a camera and an infrared diode behind the point to read a pattern of dots. The pen uses the photographic information to map its location against the complete pattern.

B. Processor

A Samsung Arm 9 processor runs the pen's software, including the algorithms that track its position.

Here are the battery particulars I got so far Type : Rechargeable Lithium Ion Model No.:GP1229L30

Cylindrical Cell

Nominal Dimension

(with Sleeve)

: F = 11.5 mm *

H = 28.2 mm

Applications : Recommended discharge current

65 to 650 mA

Nominal Voltage : 3.7V

Capacity : Typical: 325 mAh

Minimum: 310 mAh

When discharged at 65 mA to

2.8 V at 23 oC

Charge Condition : 162.5 mA to 4.2V for 3.0 hrs at 23 oC

Recommended

Charging Condition in

Applications

: 65 mA to 260 mA (0.2 to 0.8C)

Charge termination control

recommend control parameters:

Taper current 0.05C at 4.2 V

Clamped Charging

Voltage

: 4.2 V +/- 0.05 V

Service Life : >500 cycles (70% of typical

capacity)

Weight : Approx. 8.5 g

Internal Resistance : 150 mW max. at 1000Hz

Ambient Temperature

Range

: Charging : 0 to 45 oC

Discharging : -20 to 60 oC **

Storage (1 month) : -20 to 45 oC

Storage (6 months) : -20 to 40 oC

Storage (1 year) : -20 to 35 oC

the battery is not consumer grade so we'll have to find it as well