[LoneSnark]

Did you repeat the tests and average the results? If so, then your results do seem significant. However, if you did not then it seems likely that the significance was lost in the system noise.

Your views on voltage and current are absolutely correct. The phone compensates for voltage drops by drawing more current in accordance with P = I x V. While transmitting, the transmitter chooses a power level, P, to transmit at and the dynamic regulator chooses an I and V to satisfy it.

That said, the system is not as simple as that. dynamic (or switching) regulators are rarely that simple as they introduce their own efficiency on top of their energy conversion. And it just so happens that dynamic regulators tend to become less efficient as input voltage drops. What this means is, as battery voltage drops the power drawn from the battery increases, not just the current.

Psystem = Pbattery x %efficiency

So, if the system is consuming 1 watt and the efficiency is 90% then the battery is supplying 1.11 watt. So, if the battery voltage is 3.8V then the current supplied would be 292mA.

However, if the battery drains and voltage drops to 3.7V and the efficiency drops to 80% then the battery is supplying 1.25 watt, or 338mA, just to supply the system with that same 1 watt.