Update on my Volt issues.

Chevrolet are taking my Volt away next week to see if they can get to the bottom of the strange behaviour I've been seeing, so I put together a quick summary of how it behaved after the garage had updated the software.

Almost every time that I drove the full battery range (or close to the full range), the remaining range dropped very rapidly toward the end of the trip. 3 times when the car was parked with 12 or fewer miles remaining several miles of range disappeared while the car was stationary. Twice when I had used all of the battery I found that after leaving the car for a bit it then started up in PPR mode.

Date	Morning Range Estimate	Actual	Remaing range estimate	Notes
19 Sep 2013	38
20 Sep 2013	38
21 Sep 2013	40	39.7	0	Last 6 miles of range went in only 1.3 miles
22 Sep 2013	41	35.6	5	Dropped from 12 miles range to 5 miles while stationary
23 Sep 2013	43	32	12
24 Sep 2013	44	35.9	8	Range dropped by 8 miles in last 4 miles driving.
25 Sep 2013	44	40.9	0	Last 10 miles of range went in 3.2 miles.
26 Sep 2013	44	36.5	2	Range dropped from 8 to 5 miles over last 0.7 miles, then dropped another 3 miles while stationary (so altogether lost 6 miles range over last 0.7 miles).
27 Sep 2013	-	-	-
28 Sep 2013	43	44.3	0	Last 10 miles of range took 4.3 miles. On returning to car got Propulsion Power Reduced
29 Sep 2013	43	42.3	0	Range dropped from 12 miles to 2 miles while parked. Last 2 miles of range only lasted 0.7 miles.
30 Sep 2013	45	39.6	0	Parked after 2.5 miles on petrol. On returning to car got Propulsion Power Reduced

All of the above are documented in previous posts except the last:

Sunday 29th September - disappearing range again

The morning range estimate is 43 miles. After 12 miles the total used plus remaining is 45 miles; after 24 miles the total is up to 50 miles; after 41.6 miles there are still 12 miles remaining, so an impressive 53 miles total seems on the cards. I wonder if part of the problem is the car underestimating the power used, but those 41 miles were mostly 30-50mph with few stops, and a comfortable 15-17C, and I have managed 51 miles before, so perhaps the estimate at this point  is believable.

Unfortunately, an hour and a half later the car hasn't moved, but 10 miles have disappeared from the range. Only 2 miles remaining.

I go out for a short drive, and after less than 1 mile, I'm on petrol. Total energy from a single charge seems to have been 8.5kWh. Total electric range just 42.3 miles.

That seems pretty conclusive to me. The software upgrade may have changed the behaviour slightly, but I still get unexpected PPR, and up to 10 miles of range disappearing while the car is parked. Next stop is to get the dealer to talk to Chevrolet again and see if they can get to the bottom of this.

Edit: overnight recharging took 11.6kWh which works out at  3.1kWh overhead. Online forums suggest that for a 10.5kWh charge around 12.5kWh to recharge would be normal. I find this very interesting because that suggests to me that the car used maybe 1kWh more power than displayed, but I also lost about 1kWh from the battery capacity.

Saturday 28th September - Propulsion Power Reduced

I think that over the last week I've seen pretty conclusively that range still drops off sharply any time I stop with only a few miles remaining. So the big question has to be what happens if I keep going instead?

Morning range estimate is 43 miles. I go shopping and recharge, still 43 miles:

 After driving 18.7 mile, 24 miles range remaining (41.7 total).

Strangely another 13 miles driving only lost 4 miles from the range. The expected total range for the charge has now gone up to 51 miles.

I didn't stop to take pictures part way, but with 40 miles elapsed the estimated range was still 10 miles. Just over 4 miles later it was all gone. Total battery range 44.3 miles then 7.8 miles to our destination.

 We stopped for 25 minutes, then as soon as I restarted the Volt:

Propulsion Power Reduced lasted a couple of miles and then cleared itself. We stopped for a bit and when we returned to the car it seemed that PPR had recharged 7 miles of range and nearly 2kWh (although we actually only got a bit over 5 miles):

So there you have it. It seems that despite the software upgrade I'm still getting propulsion power reduced. :-(

Edit: FWIW, the overnight recharge took 11.8kWh.

23rd to 27th September - Range drops sharply when low

Monday 23rd

On Sunday the Volt said I had used 7.8kWh. The meter says it took 10.4kWh to recharge. So Saturday nights recharge of 10.3kWh had a 1.7kWh overhead but Sunday's 7.8kWh recharge had a 2.6kWh overhead.

For Monday there;s not a lot to report. Estimated range in the morning was 43 miles. I drove 32 miles (morning and evening) and had 12 miles range remaining. That seems about par for the course, nothing odd happens until the battery is getting low and I didn't take it low enough today.

 

However, I see my 7.2kWh used on Monday took 10kWh to recharge. That's a 2.6kWh overhead. For some reason the less energy the car records using the more overhead there seems to be recharging. (Absolute overhead that is, percentage overhead I would expect to get higher.)

Tuesday

Morning range estimate was 44 miles. The trip into work lost slightly against this, the trip after work gained a bit.

Interestingly, here I drove 5 miles and the estimated range remained the same. My guess would be that the day warming up (11C first thing but now 18C) had an effect on the battery consumption.

The last 4 miles today dropped 8 miles off the range. Unfortunately I didn't have time to go any further, but I think it was beginning to drop quite rapidly at the end.

8.9kWh used, overhead on recharging 2.0kWh.

Wednesday

Morning range estimate 44 miles, after 13 miles I have 29 miles range remaining (42 total), after 28 miles for the day I have 21 miles remaining (49 total!), after 37.7 miles I have 10 miles range left (47 total). Then it starts to get interesting...

 The last two pictures were taken when I stopped for some shopping at 6:17. I got back to the car about half an hour later, and although the odometer has ticked over to the next mile this next picture was taken at the traffic lights just a couple of hundred metres down the road. When I set off again the range began counting down rapidly.

 Two miles further on and the range has dropped to 2 miles.

And a total of 3.2 miles after the range estimate said 10 miles, we're running on petrol. Also that appears to be 2.0kWh used for 3.2 miles which I think would be pretty well impossible even if Oxfordshire was moved to the Alps.

It seems to me that the software update has changed the behaviour here. Where previously a stop of maybe 10 minutes with 12 or fewer miles remaining resulted in a large range drop when I came back to the car, now the range drop is being smoothed out. It still happens, but only after I restart the car at which point the range drops every few seconds and the kWh meter ticks up alarmingly quickly.

However, on Sunday it seemed that leaving the car for hours rather than minutes still results in a sharp drop and reduced total (apparent) consumption.

Thursday

Morning range estimate still 44 miles:

 Dropped one mile off the range during the day:

After 32 miles, 16 remaining which would give a total 48 miles if it stayed that way:

... but a mile later it's down to 13 miles range which gives 45 miles total, pretty much in line with the morning 44 mile estimate.

... and after 35.8 miles total I have 8 miles range left, right in line with the morning 44 mile estimate.

I stopped for about 10 minutes, then drove the remaining 0.7 miles home. Over that last 0.7 miles the estimated range dropped by 3 miles.

When I got home, I decided to see if I could replicate the sort of drop I saw on Sunday, so instead of putting the Volt on to charge I left it for 2 1/2 hours and sure enough another 3 miles disappeared from the range.

Friday

On Friday I gave the Volt (and my phone's camera) a rest. Overhead for the recharge seems to have been 1.9kWh.

Summary

The behaviour does seem to have changed a bit with the software upgrade. I'm pretty certain there's a repeatable sharp drop to the range any time I stop with 10 miles or less remaining. It no longer seems to drop significantly while the car is off unless I leave it for several hours.