The Amp Hour measurement of a battery is a measurement of how much energy can be taken from the battery. If you multiply the Ah capacity (eg 35 Ah) by the average Voltage (eg 320 Volts for the PHEV battery), you get 11.2 kWh (P=V * I for those who are electricians). This figure in kWh you are probably more familiar with from your household power bill or Chademo fast charge display. So Ah gives the true battery capacity that you can directly compare to other EV as it only depends on the battery age and usage, and does not depend on your driving style, hills, passenger and luggage loads, tyre pressure, heater or air conditioner usage etc. Battery degradation is important as it does diminish the range that you can achieve in your EV.

Lithium batteries degrade over time, when exposed to very high or low temperatures, and also with use (EV distance). The quickest loss of capacity is when the EV is new, and then the loss of battery capacity slows down so the "curve" should level out a bit as the battery gets older. The expectation is about 80% of original capacity after 10 years. This is the "PMC" (Percentage of Manufacturer's Capacity) percentage displayed in our App EvBatMon. Note that some EV "hide" the full capacity of the battery so a particular EV may appear to hold its entire capacity for the first few years.

Another interesting thing to note is that after a full charge you will get the best distance if you drive your EV straight away. This is because the battery loses some of its energy (something like about 5% in the first 24 hours) just sitting in your garage. This is the case with all Lithium batteries, and using the battery straight after a full charge is also good for the battery. Some EV (eg Tesla) even allow you to stop charging at 80% etc so the battery does not sit fully charged for extended periods.