Sunday 28th July, The Mystery of the Missing Range

Good news today, I didn't get PPR mode at all. Better news, I now have the photos to demonstrate the alternative to PPR: the vanishing range estimate.
After the overnight charge I have 46 miles estimated range this morning.

 Drive 26 miles and I have 24 miles range remaining. So far so good.

After we've been parked for half an hour, the range estimate has gone up by 1 mile. I do like the Volt when it is behaving itself.

11 miles later, 10 miles estimated range has gone, we've used 7.6kWh of the normal 10.4-10.8kWh I would expect to get from a full charge. We park at Peartree Services north of Oxford to use the facilities:

10 minutes later we return to the car, but what has happened to the range? The car has been sitting switched off for 10 minutes, but somewhere 9 miles of range have disappeared:

The info display hasn't changed. We've still only used 7.6kWh but we now only have 6 miles remaining.

 We parked in Oxford for a bit which. Nothing interesting happened to the car:

A couple of miles further on and we hit the end of the battery. 8.7kWh used, approximately 2kWh gone AWOL:

 Home again:

What I think I'm seeing here is that at some point as the battery discharges it suddenly loses voltage equivalent to about a 2kWh drop in available charge. If it happens while the car is off I lose about 9 or 10 miles of range. If the remaining range was less than 9 miles then when I return to the car I usually get PPR, otherwise I just lose it from the range estimate. If it happens while the car is on then I see the range dropping suddenly: so I've previously seen it go from 10 miles to 0 in about a mile of slow flat road, and I guess on yesterday's PPR it tried to go from 2 to -8. This is just my opinion of course, there could be something much more subtle happening.