The main battery compartment is a tough nut to crack. Five screws (hidden by some hard to pry off covers) aren't all that hold this case together.

As we finally succeed with some gentle heating and "good vibrations" we snap open the case, breaking one-time-use clips in the process. Bad news for battery cell replacements.

We finally reach the prize: 20 Panasonic NCR18650PF Li-Ion batteries! Panasonic is a good (safe) brand, so recharging should be a breeze, even if individual replacement won't be.

The battery pack also has a battery management system (BMS) circuit board.