One of the cool things about being in the Mini E trial lease program is that I can basically do what I want with the car. When the program ends this fall, I just hand back the keys and I’m not liable for anything. That’s allowed me to do things with the car that I wouldn’t necessarily do if I owned it, like: frequent deep discharges; driving it when the battery temperature was extremely high; racking up 54,000 miles in 22 months; and charging it constantly.
All of these actions will most certainly bring on early degradation, something I would not want to do to a car I paid for. However this is a test car, and we have BMW’s blessings to drive it and charge it as hard as we want without worrying about the consequences. In this way, we all learn about the limits of this electric car.
BMW confirmed that I have the most miles of all the 612 Mini Es produced, by a long shot—probably 20,000 miles more than anyone else. I have only had the car for about 660 days so I charge it 1.5 times per day. I cannot imagine anyone has charged another Mini E even close to 1,000 times. I have basically driven it the equivalent of what a normal driver would over the course of three years—if you figure the average person drives 15,000 per year and charges their EV once a day.
Data Driven
Every time I plug the car in I record the miles driven, amp hours per 100 miles used, estimated remaining range, outside temperature, and a few other things. I have a lot of data on the range of the car and now that I’ve charged it more than 1,000 times I thought I would share the range information with the Plugincars.com community, especially since I see so many people here ask about battery longevity and degradation, as well as cold weather performance.
Some of you may remember a few months back when I took offense to an article written in the Washington Post where Charles Lane wrote that an EV can lose up to 50 percent of its power with a 10 degree drop in temperature. My response? That’s absurd. I have the data—complied from 22 months of driving the car 54,000 miles—that proves it. I have recorded driving in outside temperatures from 105 to -6 degrees.
I broke up the data into two groups: the first year and the second year. I have only had it for 10 months of the second year so certain temperature groups—like 60 to 70 degrees—didn’t have as many data entries for the second year. Still, with over 1,000 entries, I think it’s a pretty reliable sample. I drive the car hard, mostly highway miles—70 to 75 mph unless I really need to stretch the range. I use the heater when it’s cold and the A/C when it’s hot. I charge my cell phone and have a GPS plugged in all the time. I don’t drive it to see how far I can get it to go. I just drive it like I would any other car.
18 Miles Past Zero
I have never actually driven the car until it stopped so the range is really an estimate. Plus, the car will still drive 10 miles to 20 miles past zero range remaining. It’s a built-in safety that BMW decided to offer. When the car actually says zero miles remaining, you still have at least 10 miles left. The furthest I have driven past zero was 18 miles. On that day I completed a 130.1 mile single-charge drive. When you really have only about 4 miles left a large battery icon appears and the car goes into reduced power or “limp mode” that’s when it’s really time to get to where you’re going. I have only seen the icon 5 times so far, coincidentally the fifth time was this morning.
Please remember the Mini E is a test vehicle, with really no thermal management to speak of other than a couple of fans that blow cabin air over the battery modules. In fact, in the summer when it’s really hot outside, the batteries can get so hot that they won’t accept a charge until they cool down and the car can even go into reduced power mode to keep them from really overheating. Even though I think it’s a fantastic car, it’s not a polished, production ready vehicle and lacks a more sophisticated thermal management system. Please feel free to ask questions, I’ll be checking back to answer.
One thing I want to clarify. In the two pictures of the SOC display above, the one on the right shows a battery temperature of 116 degrees and the one on the left shows the ambient temperature being -2. The one on the right has a warning icon that comes on if the battery temperature gets above 115 degrees, if it gets much higher, the car goes into reduced power mode in an effort to cool down the batteries. It will not accept a charge if the batteries are this overheated.
On the day I took this picture, it was 101 degrees outside and I just completed a 35 mile trip of all highway driving with the A/C on full blast the whole time.