The ego-c upgrade batteries have a button that change colors, and the ability to change voltage. Normally the button glows white, when charge is below about 50% it turns light blue. When they get about 10% it changes to a darker blue. This is all regulated at about 3.3 volts.
But - you can turn it off using 5 clicks, then hold down the button for about 5 seconds and it flashes yellow. Turn it back on and the button is yellow when depressed, and the battery puts out it's full power (about 4.2 volts). It is now in "unregulated" mode.
I really prefer these batteries, as they are "passthrough" types. I have several computers and chargers at home, and USB in my car, so I don't have to go look for a charger. Just grab a USB cord (which I keep on all my computers for charging my kindle, gps and many other things) and plug it in.