Mini E's Range Shrinks In Cold Weather, Insists Batteries Were "In The Pool"

Winter brings cold temperatures. Cold slows down chemical reactions and can play hell with the performance of healthy batteries. As expected, Mini E drivers in the Northeast are seeing much-decreased range from their lithium-ion packs. Laws of physics FTW, y'all.

Ahh, George Costanza. You brought many wonderful notions into our life: The Summer of George. Art Vandelay, importer/exporter. That whole "believe it or not, George isn't at home" answering-machine message. But mostly, we remember you for the Hamptons shrinkage thing. Don't ask us why, but it felt strangely . . . familiar.

And so it is winter, and Mini E drivers are seeing the same kind of shrinkage, albeit from a battery pack. A recent article in the Washington Post stated that Mini E users were experiencing an average twenty-percent range drop when cold temperatures hit, but predictably, individuals in the Northeast have seen greater losses. One E leasee posted on GM-Volt.com that, after 7700 miles, his car has suffered what he calls a "pronounced decline" in range:

On a recent trip at a temperature of 23 degrees Fahrenheit and including a two-hour 110 volt charge in the middle, the battery meter hit zero miles/zero percent after just 55 miles (see graphic). The car is billed as having a 100 mile range . . . My commute is 60 miles round-trip, mostly highway and at about 60 to 65 MPH with accessory heat running. It isn't clear if the battery charge level detection circuitry has become more inaccurate in the cold, whether the battery is aging and losing range, or if range is actually reduced in the cold. I suspect all three factors are in play with the latter being most important. In 65 degree weather, I can extrapolate roughly 75 to 80 miles of range on the same commuting cycle.

So in the cold weather even with a 2 hour charge at my office in the midpoint of my 27 mile each-way commute, I find myself regularly drving for the last several miles with the battery meter measuring zero miles and zero percent. It is disconcerting. There is also some noticeable power fade, though I dont push it much in that situation as you might imagine. After stopping the car and letting it rest though, I find the meter could come up to as high as 10 to 15 percent.

Predictable, right? Lithium-ion batteries are known for their relative stability across a wide range of ambient temperatures, but there's no getting around the laws of physics: Battery performance (and, in some cases, life) drops when the mercury falls. Some manufacturers — most notably Tesla, with the extensive battery-management equipment fitted to its Roadster — attempt to end-run this sort of thing by protecting the battery from ambient temperature changes. Some are successful, some are not.

Admittedly, the Mini E is essentially a public proof-of-concept, a public experiment that bears little resemblance to an ordinary production vehicle. The 500 individuals who opted to lease one from BMW did so knowing that they were part of a large-scale science and marketing project, one that lacked a certain amount of R&D. Still, there's no getting around the obvious:

"Towed! After only 87.8 miles…Sheesh!"

Public or not, shrinkage sucks.

[GM-Volt]