PiP/Volt January 7-11 Switcheroo

Quick update:

I downloaded the mileage and EV vs. gas usage records of the Volt from OnStar but had some problems with downloading the charging records. I'll try again tonight. Also cross checked a bit with downloaded ChargePoint records to compare with OnStar. I seem to see full charges taking about .5 - .75 kWh less in colder temperatures (40's) than in summer.

This morning's 45.5 mile commute into work was all battery with an estimated 2 miles of range remaining. That's a surprise since yesterday I only got 40.6 miles of range. The temperatures were about the same (37F at work when I arrived).

Not sure why the big change. I did add 3 psi to the tires yesterday from 38 to 41 (during a trip to the dealer 1.5 weeks ago an for oil change and tire rotation they reset the pressure to 38). Also, there were some slower 20-30 mph stretches on the highway and the last 3rd of the trip was light enough that the automatic headlights turned off.

 

That could be part of it. I did a full recharge overnight (early Saturday morning) and then drove 6-8 miles on Saturday and didn't plug it back in until Sunday night to do a delayed top off charge. So, it would have only added 2-3 kWh to the battery early Monday morning and may have added less than usual on a cold-soaked battery.

 

My assumption is that the battery just holds 500-750 Wh less due to chemistry and cold temperatures rather than the difference representing "wasted" temperature management overhead. Less energy held (charged into) in the battery is then part of the overall reason for lower EV range in colder temperatures.

In other words, at least in part, you have less EV range in the winter not because of lower Wh per mile efficiency but just because the battery can't hold quite as much charge as it can during warmer weather.

 

Unexpectedly good results continued:

I managed to charge at 120V this morning at work and then grabbed some additional time at 240V on an AVCon adapter that a LEAF owner has. Altogether, I got an extra 36 miles or so of predicted range.

After leaving work I did some minor shopping and then headed home on highway 280 which goes along the coastal mountain range. Up in the hills my battery gave up and I switched to gas for the last 25.7 miles. I ended up burning 0.46 gallons for about 55-56 hybrid mpg.

There might have been a small altitude drop on the way toward home but not much. My engine usually starts on flat highway on 101 at coastal elevation (50 ft. or less) and then ends at my home at around 600 ft. elevation so my typical gas mpg is arguably artificially low.

Overall, I did 78 miles on battery today and the last 25.7 on gas for a total trip of 103.7 and a total gas consumption of 220 mpg. I don't have an OnStar record of my work charging today but I seemed to do well so I'm guessing it will be 25-27 kWh / 100 miles today.

I'm still working on the records from last week.

 

The temperature was 37F degrees again when I arrived at work on battery power. This time traffic was clear although I traveled behind a truck (not closely) at 53 mph for a few miles knowing that I otherwise might end up switching to gas before getting to my destination.

As I pulled in at the coffee place 1/2 mile from work I was showing 1 mile remaining in the battery after 44.9 miles of driving. After I restarted the car it decided to begin in hybrid mode but I made it the remaining 1/2 mile to my parking spot without starting the engine.

 

Evening Volt update:

I was able to get about 26 miles of estimated range (kWh TBD) in a single 120V charging session at work I started after arriving at work.

With one side trip after lunch, I ended up driving 69.9 miles of EV and 45.3 miles in hybrid mode for a total of 115.2 miles on 0.89 gallons of gas.

That works out to 51 mpg hybrid (50 mpg if you don't count the 0.8 miles on battery in hybrid mode between coffee and work this morning that I noted in my previous post). That's a combined total of 131 mpg for today's drive.

This time the gas engine started on flat road with under 100 ft. elevation before heading up through the highway 280 rolling hills again and ending at my house with about 600 ft. elevation. I was getting about 52.5 mpg before heading up the final mile or two of elevation gain.

Now, I'll get back to work on writing up last week's comparative efficiency numbers. Oh, and also changing my profile picture from PiP to Volt...

 

Morning update:

Exact same commute as yesterday.

end of story.

 

The Volt will clearly consume less gasoline. I used around 4.6-4.8 gallons (from memory) in the PiP for 4 complete commute days. I will probably use less than half that amount while using the same level of diligence around opportunity charging during the day. I was getting a total of about 85-95 mpg in the PiP and with the equivalent driving and charging effort I get around 180-240 mpg in the Volt for my commute pattern.

As for comparing fueling costs, CO2 emissions, etc. I will cover that in a future post.