A Cold Mirage?


Brrrrrr. There’s no doubt about it – when the thermometer dips, so does the range on my MINI E’s high-voltage batteries. And it’s been a hot topic of conversation among the MINI E pioneers in the northeast for over a month now that the weather has been so cold.

Most drivers are reporting anywhere from a 15-20% hit on the range displayed. And that’s in line with what I’m seeing as well – at least for a couple of hours. After that, I’m seeing some evidence that this “cold tax” is just a temporary reaction, and that those missing electrons aren’t really “gone”, just in hibernation (excuse the wordplay fun on all things cold…I can’t help myself).

During the summer and fall, my 45 mile morning commute would generally leave me showing 52% or so on my charge meter as I parked my car. I’d then plug in using the 110-volt cable, work all day (wink) and come back to a 75% charge at night, which meant I was getting between 2-3% recharge per hour.

Now I sometimes pull in to my parking space in the morning showing just 35% left on the meter. But when I come back in the evening – with the batteries still exposed to the same frigid temperatures – I still am greeted with a 72% meter. So either my recharging capability has more than doubled, or those extra 10-15 percentage points were really there all the time – just not being seen by the meter.

Charge accuracy, you may recall from earlier posts, is a pretty fuzzy thing, at least with this model of electric car. The algorithm tasked with calculating the charge isn’t yet smart enough to be more than a general gauge of the state of charge. What is interesting however is that the settings seem to over-estimate the actual drain that the cold weather will have, anywhere between 15-20%.

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3 responses to “A Cold Mirage?

  1. I froze my battery for the first time last week, it actually stopped charging. Ever since I have been leaving a small space heater in the passenger foot well on all the time. The battery is usually at least 70 degrees now, and the small drop I had seen in apparent range is gone.

    But I agree, that apparent drop in range from the cold is just a calibration issue.

  2. Pingback: Knowledge is Power « The Electric Ride: MINI E #217 Road Test

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