Now is the best chance to take an indellible marker and write the polarity of every cell on the rubber of the holder.

Pry off remaining tabs. Maintain all safety precautions.

Cells will push out from bottom of holder. (The missing one was found in my coffee).

The cells inside were Model: LGEAMF11865 (ICR18650MF1). Capacity: 2150mAh Rated. Voltage: 3.65V Nominal. Charging: 4.20V Maximum 1075mA Standard

I chose to replace with: Manufacturer: Sanyo/Panasonic · Model: NCR18650GA · Size: 18650 · Capacity: 3500mAh · Maximum Discharge: 10A

Make sure to balance the cells by pre-charging them all. You require 21 so you be prepared to do it in advance.