Fully charge the battery set and take a couple shots; let the camera sit 15 minutes or so. Enable and check the camera readout for actual battery voltage, then set MAX to that voltage. This takes the "glaze" off the newly charged battery and gives you a somewhat realistic MAX voltage.
Fast charging won't recharge a battery as fully as a slow charge overnight. New batteries require 3 or 4 charge/use cycles to realize their full potential charge. As batteries age and get abused (run dry, left uncharged) they lose their ability to take a charge. Different battery sets can easily yield different performances. All these things affect how well the cameras calculated battery life coincides with reality. Check and set the voltage after doing the type of charge you normally do with the type of batteries you normally use.
Rufus
