Monday 29th July

Nothing much to report today.

Estimated range this morning was 48 miles, but it looks like it was heading for about 45 miles actual range. As on Friday I think the range was tailing off faster toward the end, but not significantly enough to be sure or to make a fuss about.

There was an interesting suggestion from Steve-o on gm-volt.com:

That's excellent documentation, and your explanation at the end of the July 28 entry sounds very plausible. If this were a laptop, I would say one cell of the battery had shorted, which often causes a laptop battery to drop from 15% to zero in a split second. Of course, there are a lot more cells in a Volt battery than a laptop battery, but I wouldn't be surprised if something like that were going on, or maybe a controller issue as SteveC5088 said, since you have had two batteries. It seems like the dealer should have some kind of diagnostic tool that could test for this issue.

I must read up on battery faults, but I have this horrible feeling the problem may indeed be with the battery.

Anyway, a few photos from today to demonstrate the mileage. Starting with the 48 mile range estimate:

 Arrived at work 14 miles later, 15 miles gone from the estimated range.

 Still showing 33 miles when I left work, 20 miles later the range has only gone down 18 miles:

 3 miles further on, but 6 miles gone from the range:

 and another 2 miles and range has gone down by 3 miles:

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.

Saturday 27th July, Propulsion Power Reduced

Today's trip is where things get a little bit more interesting.
First the really boring bit. After the overnight charge I had a 43 mile range estimate. Drive 4 miles to shops, fully recharge while shopping, drive home and recharge again. Range now says 44 miles.

 Drive 24 miles to Oxford M40 services, partial charge of 2.21kWh bumps the remaining range back up to an estimated 32 miles remaining:

 Arrive Aylesbury at 13:23, 21 miles range remaining:

 Leaving Aylesbury at 15:22, the range estimate has gone up by 1 mile but that's not unusual.

At 10861 miles the range estimate was reading 2 miles, and I was on the A40 near Wheatley doing about 50mph. This road is not in a mountainous region.
Within the space of about 3 seconds the range went from 2 miles to petrol engine and propulsion power reduced mode with the engine desperately trying to make up the charge. I pulled over as soon as there was a suitable side road and took this picture:

That isn't normal behaviour for a Volt. I wasn't accelerating, I wasn't driving up a hill, I was reaching the end of the available charge, but 12.9kWh is about right for 10.8kWh (which is about what I get on a normal day) plus 2.21kWh top-up (less a little charging loss). This is actually new behaviour I haven't observed before: previous PPR incidents have all been when I return to the car having parked with lowish range estimate.

At this point, since I'd stopped for the photo, I turned the car off and on again and PPR cleared so I was back to normal acceleration.

16:43, arrived in Faringdon and parked. There was a hill nearby, but we parked at the foot of the hill and walked up.

17:48 returned to the car and started up straight into PPR mode again:

 I drove for a mile or so then stopped and powered the car off and on again to clear PPR mode then drove home.

Friday 26th July

Day one of the diary. As I mentioned in the last post I collected my car from the garage who've been doing a great but so far unsuccessful job of trying to find the source of my Volt problem.
I got home with 17 miles range remaining and plugged in to charge. A few hours later the car was showing 27 miles range at 10765 miles.

12 miles from home, parked with 22 miles range remaining. I only lost 5 miles from the estimate, but given that the garage have spent a week trying to run the battery down I'm not surprised if the range estimates take a while to settle down.

After 20 miles there are 4 miles estimated range remaining. Slightly less than the original estimate but nothing outside plausible variations in range. The battery finally reached 0 and switched over to petrol 4 miles later at 10789 miles so I got about 24 miles from the initial 27 miles estimate.

Conclusion: inconclusive results here, it looks to me as though the range tailed off rapidly from 17 to 10 miles remaining, but I wouldn't expect this to convince a skeptic.

Keep a diary...

Friday 26th July 2013, I collected my Chevrolet Volt from the garage where it has spent the week as they try to track down a problem of my car spontaneously losing several miles of battery range or going into 'propulsion power reduced' mode unexpectedly because there is insufficient charge remaining in the battery for normal driving. The bad news is that they haven't managed to find anything, but worse Chevrolet UK are denying that the behaviour I am seeing is anything out of the ordinary and point to page 5-44 of the car manual as proof:

The garage admits that they saw the issue when they had the car previously, and that their demonstrator car hasn't shown the issue. I pointed out that I've also asked online at gm-volt.com and nobody there thinks my car is behaving normally. All the garage can suggest is that I keep a diary for the next few weeks so they have some hard figures to put to Chevrolet UK.

So here it is, my Chevrolet Volt diary where I intend to keep a close record of miles covered, range estimated and achieved, and any strange goings on such as dashboard information messages.
First a brief introduction to the problem as I see it. This is what I posted on gm-volt.com just over a month ago:

I have an issue with my Volt that several times now when I've parked with the battery range close to 0, when I return to the car and start it I get 'Propulsion Power Reduced' and the engine revs madly for the next few miles. So far I've seen it happen at least 3 times. The first time the car showed 5 miles battery remaining when I parked it and then 10 minutes later it was PPR. In all cases I haven't been driving up any hills.

So far as I can tell it doesn't happen again when the car has been running on ICE for a while: it's just an issue around the changeover point from battery to ICE.

The garage has looked at it and can reproduce the problem when they drained the battery. They say though that they aren't sure it is a problem and perhaps all Volts do it. Their demonstrator is out on loan at the moment but when they get it back they'll see whether it does the same.

I don't believe that 'all Volts do it' or I suspect I would see some comment about it on this forum. My question is, has anyone else had a similar problem (and if so did you resolve it and if so what was the resolution)? Alternatively, if there's anyone who regularly runs the battery down to close to zero but doesn't have this problem, please can you say so that I can show the garage that it's not 'normal'.

and a bit later:

I think my Volt has had the PPR message 7 times in total:
First time was when I was driving along with more then 20 miles estimated range remaining. I called the dealer from whom I bought the car and they collected it a few days later.2nd time was when they were driving it back to the garage (they're about 100 miles from me). They replaced the battery.
3rd time was when I was driving up a steepish hill in the Chilterns. There's no way you would consider the Chilterns to be mountains, but some of the roads are steep and go up and down a lot. PPR surprised me here, but I have no particular complaints.
Now the ones that concern me:4th time I came off the A34 (so 70mph) and parked with 5 miles estimated remaining. PPR came on when I returned to the car. No significant hills in the area. Link to google maps
5th time was near Redruth in Cornwall. I'm not sure what range was remaining as my wife was driving, but it was pretty flat.
6th time was back in Oxfordshire. Again no mountains nor even hills in sight: Link to google maps. That time I had been trying to drive carefully in the hope of breaking 50 miles, but I reached my destination after 49.8 miles with an estimate 0 miles remaining.
7th time was whatever the garage (new dealer: they're only 9 miles from me!) were doing with the car today. I've no idea where they were at the time, but they're based here, so I doubt many hills were involved: Link to google maps. They said they ran it down to 2 miles range remaining then turned it off and on again to trigger the PPR message.
Steve-o: yes, it is when starting the car, PPR comes up instantly. Turning it off and on again at that point doesn't seem to help, driving a few miles and then turning off and on again clears it.

I'll see what the garage says when they've tried to reproduce the problem with their demonstrator and when they've managed to get a response from Chevrolet.