The Book's display battery is actually easier to remove than the cell in the Surface Pro 4.

This is likely due to the fact that it's smaller and has less surface area—i.e. less adhesive.

While the Surface Book is intended to be used while docked, its display packs a 18.0 Wh, 7.5 V, 2387 mAh battery and an alleged four hours of battery life.

Judging by the Surface Pro 4's 38.2 Wh battery, and the iPad Air 2's 27.62 Wh, we expect to find a decent cell in this Book's base to meet the spec'd 12 hour battery life.

After all, 3000 x 2000 pixel displays have a habit of using a lot of power.