The Flashpoint VB-26 is the rechargeable Lithium-Ion polymer power cell for the Zoom Li-on X and Zoom Li-on III Speedlights. The new 7.2V, 2.6mAh, 18.72Wh, Li-ion Battery is comprised of two 18650 cells, with a proven track record for performance, reliability, and longevity. The packs can be recharged in about 3.5hours, using the VC-26 USB Charger. With an estimated 480 full power shots inside, there isn't much room for shorts.
An extra battery is always a good idea, even if it is likely to never die on you. This cell delivers 480 full power shots on a single charge, the power of anexternal battery pack INSIDE your flash.
Go ahead. Shoot harder, faster, stronger, longer.