Does it say "Upgrade" on the side? It might not if it's generic, but there is a type of battery called an eGo Upgrade that has two different operating modes. They call it variable voltage, but it's not exactly. I'm not going to go into detail about how they work, in case it's not that kind of device, but here are the commands for the upgrade. Give it shot, it might work.
It has two output modes: “Regulated/Constant” and “Unregulated” (Joyetech calls that mode “Battery Voltage.”)
Click 5 times to turn on
If the button is white or blue, you are in the Regulated mode
If the button is orange, you are in the unregulated mode.
To switch modes, click the button 5 times to turn it off. Hold the button down until it turns white/blue or orange, whichever is different from the last mode you were in and it will blink 3x in that color. Click it 5 more time to turn it back on.
ETA: Let us know if it is that sort of device and we can explain it further.