I had an... exciting... drive to work yesterday that I thought was worth sharing. I try to do most of my charging at work (because free). This works out fine most days during the spring, summer, and fall as I can drive the round trip from and to work with more than 40% battery charge remaining. Well, in the winter the e-Golf's efficiency drops quite a bit. Mostly a direct correlation with temperature. I can compensate for this by adjusting the minimum state of charge setting in the car. That way when it is plugged it charges to at least that much, regardless of other settings. I usually have this at 40% during warmer days and 50% during the winter.
Well, yesterday it was zero degrees Fahrenheit in the morning and I woke up thinking, "I didn't adjust my minimum charge level. I wonder if I'll be able to make it to work?" I walked out to the car 30 minutes before I needed to leave: 21 miles of range. It's a 14 mile drive, but the car usually uses 20 miles of indicated range for the trip. Yikes! I immediately got the car charging to get what extra range I could before I needed to leave. It uses 20 miles of indicated range because the morning drive to work is colder than the afternoon drive home and it uses the efficiency last trip as a guide for the next one.
A half hour later I unplugged the car and got ready to go. 26 miles of range. Ok. That should be fine. Then I turned on the ignition and the car corrected the range down to 23 miles. Well, that's going to be tight. But I can always turn off the HVAC and rely on the heated seat to get extra range. Let's give it a try. About a mile and a half down the road, this was the dashboard:
Of note:
- I've already lost 3 miles of indicated range. Pretty normal because the HVAC is busy using lots of energy to get the interior warm (even though I did pre-warm the interior before I left).
- It's 2 degrees outside.
- The little gauge in the bottom left shows that the car is limiting maximum power because the battery is cold.
At this point, I could probably turn back home and take Mrs. ShawneeCreek's 4 cylinder Focus instead. I decided to press on and see what happens. Obviously keeping a very close eye on range remaining vs distance to work.
The drive was pretty efficient, other than the cold. The icy roads forced slow acceleration, slow regen braking, and a lower top speed. Despite all that, this was the dashboard at the stop sign 2.5 miles from work:
Ok. Six miles of range left. I should make it to work fine. But notice that max power gauge. Yeah, it is now just above the red. I'm not sure what that correlates to as I've never gotten it here before. Let's find out. I turned the corner and accelerated with my foot nearly to the floor and peaked at 22% power on the big gauge. That works out to about 40 hp. It took more than a quarter of a mile to reach the 55 mph speed limit. And you know how much power it took to maintain 55, mph? You guessed it: about 20% power. Oof. At least I'm at the speed limit.
By the time that I got to work (2 miles later) my maximum speed was 52 mph. Less good. But I made it with the dashboard looking like this:
Low battery indicator on. 4 miles of range left with about 10% charge on the battery. And still limiting power because the battery is cold and low on charge. I plugged the car in and it was fully charged 2.5 hours later.
Range is going to be tighter this week with temperatures hovering around 15 degrees, but the car works. I'm just right near it's limit. And I may have to do some charging at home. Not too bad, all things considered.
- Sean