After driving the i-MiEV for several months, I wanted to
test its capability and range under more unusual driving conditions. I knew that the car used more electricity
driving uphill than on a level surface, and it had been a while since my last
visit to the mountaintop winery near me, so I decided to head up the
mountain. The first thing I checked was
the distance to the winery from my home.
The routing suggested by Google Maps was the obvious and most direct
route. This route starts off with 11.2
miles of freeway (each way) which would draw down the battery by about 7kwh
round-trip, or a little less than half the charge. That left more than half the charge to get up
the mountain and back down. It was
another 3.5 miles to the start of the mountain climb, and 4.3 miles up the
mountain (about 1,500 feet of elevation change). I figured that if I could make it up the
mountain on 6kwh, I would get home safely.
(That amounts to 0.72 miles per kwh, which is terrible.) So I decided to go forward with the trip.
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Google Maps' proposed route up to Ridge's Monte Bello tasting room |
As I started driving, I created turn-back thresholds for the
battery consumption in my mind, beyond which I would have to turn the car
around and head home before reaching my destination. This is the sad impact that range anxiety has
on us poor fools who overthink or over-worry about their electric cars. Of course, it’s better to be prepared for
failure than to deal with the consequences of going too far up a mountain
road. As I reached the base of the road
up the mountain, the charge meter showed that I had used four ticks (which
amounts to 4kwh), as expected. So, I
continued up the hill. You can imagine
my shock after driving the first mile and watching another tick (1kwh)
disappear from the gauge. Still, at this
rate, I would make it to the winery with energy to spare, so I trudged on. The second and third ticks disappeared with
less of a shock as I noticed the rate continued at about 1kwh per mile. Finally I arrived at the winery with about a
half a charge remaining. The drive home
would use less energy, so I knew I would make it home safely.
After enjoying a modest wine tasting and giving my body a
little time to process the tasty stuff, I left the winery for my drive
home. Much of the drive down the
mountain required very little energy, and often times I was regenerating while
the road sloped downward. Nearly as
shocking as watching the first tick disappear while driving up was watching the
first tick reappear on the way back
down. This time, the shock put a smile
on my face. By the time I had reached
the bottom of the hill, I had regenerated about one and a half ticks (1.5kwh). Now I was faced with driving the remaining 12
miles on the highway with the 9kwh charge remaining in the battery (about 30
miles of range), which I could do easily.
So, in all my worry about getting up the mountain, I forgot to factor in
the regenerative effect of driving back down the mountain, which changes the
amount of charge needed to complete the trip.
So, here is the mind game about driving an electric car with
regenerative braking up and down a mountain.
I used about 3kwh of electricity to drive about 9 miles up and back down
the mountain. This rate of energy
consumption is a little worse than it is when driving on the freeway. But, the trick is that without at least 4kwh
of charge in the battery, I never would have made it to the top of the
mountain. I needed more than I used on
the whole trip just to get half-way. It is conundrums like this that have me thinking I’ll stick to being a flat-lander.