Since this has been asked so many times:
We do NOT recommend you remove the battery from the unit. It was not intended for user replacement and removal of the electronics from the Pinnacle or Pinnacle PRO's housing will void your warranty!
That said, with your background you can probably figure out how to disassemble the Pinnacle. (I will not give instructions on how to do this, but I'm sure some others on this board can help) in that case, you could potentially replace the battery. My question to you is. Why?
The battery in the Pinnacle and in the Pro is a single cell 18650 type Li-Ion battery. it is rated at 2000 mAh. Yes, you can find batteries with higher capacity ratings. What you will have trouble with is finding a replacement that has 5A of peak discharge current. I spoke to this on the Pinnacle thread: we re-formulated the batteries so that they would match with the heater core. if you use a different cell, you may find the unit randomly cut's out and stops working!
Add to this, if you remove the battery you will wipe the calibration settings and your temps will be off. May be low, and you get poor performance - or too high and the unit melts!
We have not had any reports of the batteries going bad, and don't anticipate that happening. So again, not sure why one would want to replace the battery? I realize everyone would like to have longer operating times. This is why on the PRO we added in use while charging. In order increase the use time, we would have to add more batteries, and we feel that keeping a small size was more important than long battery life.
If your looking for really long battery life, I would recommended looking into the VB2.0 which has significantly more battery capacity.