Understand iOS Low Battery logs
Your question is a great excuse to update and expand my previous answer on interpreting these diagnostic logs.

The partial charge field is a simple binary field. A zero means you didn't plug in your phone and these logs document how much usage you got out of a full charge. A one value means that you did plug your phone in after the last full charge and that the readings document more than one full charge - perhaps the phone was working for weeks and kept getting plugged in before finally running out of power. 

The log only gets written when the device literally shuts itself off after all of the power warnings.

Voltage documents the voltage of the battery when the device shuts itself off. There usually is still some charge left to power the display briefly and show you that you need to plug it in. Eventually the voltage will decay so low that nothing will run until plugged in again. 

Capacity Documents what the power management chip thinks should be left in the battery at the point the log is written. I've never seen a device where this isn't zero.

Here's one of the logs I've collected on my iPhone six:

Hardware Model: N61AP
Awake Time: 07:48:22 (28101)
Standby Time: 11:30:25 (41425)
Partial Charge: 0
Capacity: 0
Voltage: 3409 mV