My Year with an All-Electric MINI

cold weather again, and varying rates of % battery used per mile

Posted in Uncategorized by Timothy Gill on December 29, 2009

The last 2 months have been a mixed bag with the MINI E.   After the really cold October day when I only got 87 miles and had to be towed a mile to my house, we had weeks and weeks of warmer weather and I did not have range problems.  As it has gotten sometimes colder again the past couple of weeks, I have come close again to running out of juice (going as much as 10 miles after reaching 0% on the battery meter), but have also been driving less because of working at home, holidays, time off, and my wife driving the car.  My logging of my drives is inconsistent, but I am now thinking that the day I was towed in October might have been a slight aberration, as it was only the 2nd day of driving after 3 weeks of being idle (the wall box would not charge it as it was causing the breaker to break and MINI replaced it).

The next couple days could be tricky, as it is going to be in the 20’s, so we’ll see how it goes.   And not looking forward to the poor heater in this car on these colder days (when I run it).

One aspect of the driving experience I want to write about more is the inconsistent percentage battery usage readouts that I get on my commute (about 4 miles on local streets, then 37 miles on the highway, then 2 miles local to the job site, and reversed going home).  There are days where in the 4 miles from home to the parkway, it drops from 100% to 95% [rate of 1.25%/mile]; when I exit the parkway after a total of 41 miles, I am down to 39% [rate of 1.52% per mile on the highway]; when I go the 2 miles on local roads to my work site, the percentage goes back up, say to 41% [rate of -1.0%/mile]; and in the parking lot, it gets up to say 47% during the day.  The rate of drop is inconsistent and confusing to me, though it may reflect actual charge; but as a user, it is confusing.  And on the way home, it is worse:  in the 2 miles back to the parkway, it drops to 38% [rate of 4.5%/mile] and when I’ve gone 70 or so miles total on the way home, I often go the next 10 miles on the parkway with the % battery meter dropping only from maybe 8% to 3% [rate of 0.50% per mile].

So the rate ranges from 4.5% per mile to -1.0% per mile, a factor of 5.5, which is indeed odd.  I should do some precise measuring and a graph to make this clearer.  Comments, anyone?


3 Responses to 'cold weather again, and varying rates of % battery used per mile'

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  1. Doug Jacobs said,

    Is it possible that your % per mile may have something to do with the amount of braking that you have to do? If you’re driving in traffic and your brake lights are on all the time, that could substantially effect your rate of discharge.

    • Timothy Gill said,

      I don’t think so. The traffic patterns have been consistent for months and generally I don’t have much traffic. And actually, I get better mileage in traffic than driving unimpeded on the highway.

  2. Dana Welch said,

    Have they tried a special insulation package for cold climates? I remember many times having to place my camera inside my coat during cold weather shoots. Wrapping the battery in colder climates a la lada might solve the problem.

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