BR, here's the best explanation:
Battery Voltages -- Surprise!
BTW, I love and use the Riva/eGo batteries, I just wish they would deliver better voltage (like the stated 3.7v vs. the effective 3.1-3.2v) and be less prone to sudden death.
Well now, some folks may think the voltage of these batteries are a feature, not a bug, LOL. My Hello battery regulates at 3 volts and I like that. It is designed to be used with a 2.5 ohm device, and will perform about the same as a 3.7 volt battery with a 3 ohm device. My juice tastes about the same either way. The difference is that my Hello battery will maintain the same taste and TH almost throughout the entire battery charge.
My 3.7 volt battery will not do that. It starts out at that voltage, but it doesn't stay there for very long. At some point during the discharge it will be vaping at 3 volts. So what cartridge should I use? Maybe I could start out with one at 3 ohms, then change to a 2.5 ohm cartridge when the voltage drops enough. That would work. I think. I have never gone to the trouble to find out.
At this point, I need to say something about the E2. When a battery charge began playing out with an old type cartridge, I used to make some really long drags trying to get a bit of a hit before the battery shut down. I don't even notice that now. My juice actually has a better taste at 2.5 volts or less, or about when the battery shuts off.