Nickel-zinc NiZn Battery

This is a new commercially abailable battery chemistry (Wiki).  A friend got this  Powergenix kit of 4 batteries and the charger from me from our local Dollar Store.  These AA cells have a nominal voltage of 1.6 V which is a little more than the 1.5 V of the common Alkaline cell and a lot more than the 1.2 V for a Ni-Cad or Ni-MH cell, like the eneloop Ready-to-Use rechargeable batteries. 

They are marked "2500 mWh".  Using the nominal 1.6 V rating that means 1562 mAh.  For comparison a Ni-MH cell marked 2700 mHh would contain 3240 mWh.
So these cells offer more voltage but maybe no as much capacity as some commonly available Ni-MH cells.

When used the  Nikon SB-25 Speedlight the time to full charge is noticably faster.  These flashes use a switching mode power supply to step up the input voltage to around 330 V.  If the starting voltage is higher and the current capacity is about the same then more power is being applied to charge the flash capacitor.

Data sheet -

Discharge Testing