Uh-Oh, It’s Getting Cold

Yesterday a big cold front hit the northeast, plunging temperatures into the 30’s for the first time since I began running on electrons, and it looks like it’s put a big chill on my driving range.

First off, let me say that it’s still early days as far as MINI E #217 and cold weather performance go, so there’s a good chance that all I need is a few more runs to figure things out, and the symptoms that I experienced yesterday won’t be an issue. And least that’s what the optimistic pioneer in me is hoping for. Now, here’s what put the “uh” next to my “oh” yesterday.

I had to take a day-trip to Atlanta, and so I drove 34 miles to Newark Airport in the morning, with the air temp at a relative balmy 50 degrees and my charge-o-meter reading 60% as I locked up in daily parking. Now my daily experience has been that, when I am parked, the charge-o-meter would actually gain 5-10% as the batteries relax and the remaining power consolidates. So I flew off to Atlanta, comfortable in thinking that for my drive home I should have about 70% or so. But this day the weather got colder and wetter (with snow flurries dusting the area), and so by the time I returned at midnight I still had only 60% showing. Not as much as I expected, but still plenty of juice to carry me 34 miles back home.

When I first started my trip back, things looked normal – loosing about 1% charge per mile. Then about 5 minutes into my drive I noticed my charge level started dropping much faster. With 20 miles to go, I’d lost almost 30%, so I turned the heater off (a decision not without regret as it was 38 degrees outside).  At about the halfway point, I was down to 15% – which is when I turned off the radio off, leaving me alone in the cold and dark with no human contact.

With 10 miles to go, I was under 8%, and resorted to turning my windshield wipers on and off manually (I have no idea how I even thought of that, but a desperate mind is a creative mind). At 5 miles from home, I hit 0% – and I was making mental preparation to feel the “reduced performance” kick-in, limiting me to 40 mph on the Garden State Parkway so I could crawl off the ride and freeze to death in the breakdown lane. The small part of me that was still warm was looking forward to the Roadside Assistance call, but the uncomfortably-cold majority of me was still searching for other ingenious power-saving manoeuvres like the windshield wipers. Remember that scene in Chitty Chitty Bang Bang where they are throwing items overboard to maintain altitude? That’s where I was.

Luckily, I nursed it up to Exit 172 which, as previous readers will note, is the top of a 1/4-mile long downhill with loads of regen opportunity. That, along with the back-road speeds of around 40mph (for some reason at 40mph it feels like it could go forever), meant that I arrived home ok. But I still only had 2% charge when I shut down in the garage, whereas in warmer weather I’d gain 10% coming off the highway. That means I lost 30+ miles of range, and the temperature only hovered around freezing.

So here’s the surprise – I always knew that the winter was going to present range problems with running the heater because it takes so much juice to create resistance in the heating coil (some estimates are that the car will lose 14-15% range for each hour of heater use); but the cold also clearly impacts the battery pack’s ability to hold a charge. To get an idea of this, leave a phone or an iPod in a car on a frigid day with a full charge, and you’ll return to find it seriously depleted after a few hours.

So this winter is going to present a double-whammy of sorts — a limited ability to run the heater and, if yesterday’s experience is typical – anywhere from a 20-30% loss of range from the batteries. So starting with today’s commute, I’m going old-school — driving gloves and a big winter coat and hat.