Если почитать иностранный форум внимательно,то можно наткнуться на следующее:
Yesterday I borrowed a multimeter at work and measured the voltage of many of my batteries:
My standard 510 battery (TW Titan) gives around 3.6 volts.
My eGo battery (TW Tornado) gives around 3.7 volts.
A 510 mega battery (TW Mega Power) gives around 3.7 volts.
A 901 automatic battery (I think RN4075) gives around 3.6 volts.
Two 901 manual batteries (SLB) giving around 3.2 volts.
Another 510 standard battery (don't know the manufacturer and it is unbranded) gives around 3.2 - 3.3 volts.
A generic 510 PT connected to a 5v / 1000mA wall adapter gives around 4.2 volts.
I do not remember if I measured something else. Another day I will continue to measure more hardware.

Edit: These measures are taken directly from the batteries, they are not loaded measures like those of the head of this thread.