Sorry NancyR but the Series statement IS correct.
2/3/4
batteries End to End = 1 higher Voltage Battery. Common practice for Decades in Flashlights and other devices.
Many Remotes use/used Series
batteries.
Common practice of Parallel it for time between charging or replacement. Rarely(Us) for higher amperage draw.
What
vaping is doing is a bit new but what Batteries can do has been going on for a Very Long time.
I come from an industry that has worked with much more powerful batteries in many variations. Even Series parallel to boost power and longevity.