Here’s How Far My 134,000 Mile BMW i3 Drove On A Single Charge Of Its New Battery

My 134,000 mile BMW i3 had only 48 miles of estimated range when I first test-drove it. “Oh boy, I think the battery is toast” I worried before asking the BMW dealer to do a battery health check. He refused. “You’ll have to buy it first or someone else will probably snag it. Only then will we check the battery,” the dealer told me. I took the risk, and the battery ended up being toast. Sadly, BMW’s battery warranty is just eight years, 100,000 miles; my new i3 is nine years old with 134,000 on the clock. So I was screwed; or so I thought.

If you’ve been following my i3 saga — my very first foray into the world of electric cars, and one that involved me, a man who tends to buy old Jeeps, falling in love with a little carbon-fiber car with an incredibly beautiful interior — then you know that the California Air Resources Board saved my ass. Specifically, it did so via this rule, which oddly only applies only to plug-in hybrids/PZEVs, and not to fully electric cars:

My i3 is equipped with a “Rex,” or “range extender.” It’s a little two-cylinder, 650cc gasoline motor built by Taiwanese company Kymco and normally found in a BMW C650 GT scooter. With the car’s 1.9-gallon tank, the engine is there to help you get to a charging station once you’ve driven all 72 miles of EPA-estimated all-electric distance. In my case, the motor had an even more important role: It made me eligible for California’s 10 year, 150,000 miles warranty, which the dealer honored.

I will say I was skeptical at first. The dealer had initially told me it would take six to eight weeks for the new battery to show up from Bavaria, then it called me 10 days later to say the job was done. After my first, rather tame drive saw the car going 86.2 miles, I was convinced the battery had been replaced; but I have lots of questions still: Is this battery the same as the one that originally came in 2014 i3s? Is Samsung still making the same, older pouch cells? Are my batteries brand new or have they been reconditioned in some way? Surely they haven’t been sitting in a warehouse since 2014.

I likely won’t ever know the answer to these questions, but what I can do is test the battery and see the maximum number of miles it can propel my i3 on a single charge. So that’s what I did.

I’m not sure “hypermiling” is technically the right term here, in that I didn’t try to draft behind vehicles on the freeway, I didn’t tape up certain features or pump my tires up to a high PSI, and I didn’t focus hard on steady-state cruising. Plus, I did take a drive through a canyon road, which didn’t help things; also, the temperature was pretty high on day two, and then you could argue that spreading this across two days wasn’t great since on day two the battery had to condition itself for a second time to maximize its efficiency. But nevermind all that: This test is me driving as carefully as possible to maximize range from this mystery battery that a BMW dealer chucked into my i3 thanks to California’s consumer protection rules.

Driving with efficiency in mind in an EV is a little different than doing so in a gas car; gas cars love highways — their engine speeds are steady and low in high gear, they’re going a long distance over a short period of time, and they’re not wasting gas idling while not moving. EVs are oftentimes not most efficient on the highway; it takes a bit of time to get used to the fact that your most efficient route may be your most miserable one: traffic.

I kind of like this, since with a gas car your misery sitting in gridlock is joined by more misery at the fuel pump, whereas in an EV you can at least enjoy a little efficiency win while laying on your horn on the 405. And it makes sense why EVs do so well in town and so poorly on the freeway: Electric cars don’t have to idle, since their motors make lots of torque even when not rotating. I’m sure you’ve all heard that in car reviews before: “EVs make max torque at zero RPM.” But what does that mean? Well, it means that when that motor isn’t spinning at all, it can create a bunch of rotational force (this is technically not the right term, but for the layperson, that’s a good way to think of torque); imagine grabbing an electric motor and stopping it. Maybe you have a remote control car, you pick it up, and turn it on — imagine taking those spinning wheels and stopping them so they cannot rotate. You feel that force your fingers? Those wheels twisting your skin a bit as they try to rotate? That’s what it means by “electric motors make torque at zero RPM.” Your remote control car’s motor is not spinning — it’s at zero RPM – but you can feel that it’s making torque, trying to spin.

A gasoline car, at zero RPM, makes essentially zero torque. I say “essentially” because the starter motor does temporarily create torque in order to rotate the engine up to an RPM that allows its pistons to squeeze are (build compression) just enough to facilitate combustion, which pushes a piston down and gets the car idling to the point where the starter is no longer needed. Most modern cars do shut their engines off in the city, and use beefed-up starter motors to turn them on just before you need to take off from a light, but many have to sit at stop lights and idle — burning gas to travel no distance whatsoever. It’s pure waste, and electric cars don’t have to do it. At a stop light, an EV is using as much electricity as it would be while off, plus whatever is needed to run accessories and maybe your AC.

What’s more, in city driving, you’re often on your brakes. In a gas car, brakes are literally a mechanism that turns your car’s kinetic energy into friction/heat. That’s literally their job. In an EV, and especially in my i3, letting off the accelerator pedal slows the car down dramatically, but this deceleration isn’t a production of friction braking, it’s actually the resistance associated with the electric motor acting as a generator to recharge your batteries.

So in the city, EVs don’t idle, and they leverage stopping at lights to recharge the battery. What about on the highway? Well, on the highway, they deal with a lot of the same challenges as an ICE car — rolling resistance, aerodynamics, bearing friction, powertrain inefficiencies, etc. But the biggest one of all challenges is that second one: aerodynamic drag, which follows the equation: Drag equals one half times air density times velocity squared times drag coefficient times frontal area.

Notice that the velocity is a squared term, meaning your drag goes up with the square of your speed. So imagine going from 25 mph in the city to 75 on the highway — you’ve tripled your velocity, so your drag has gone up nine-fold! Just intuitively, you can imagine pushing a big car at 5 or 10 mph — maybe you’ve had to do so while trying to give someone a roll-start in their old VW Bus. That’s not too hard, right? Especially with the i3’s reasonably light weight and skinny tires, that motor isn’t doing much pushing the little carbon fiber car down the street at low speeds. Now imagine pushing that same car, but with a 75 mph wind gust blowing against you — that’s the same thing that the car has to deal with on the highway. It’s quite a lot harder to propel that car forward, and thus, it’s why the i3 tends to fall on its face when traveling at high speeds. (There are also implications associated with motor gearing, but that’s really less important here).

For these reasons, I kept the i3 in town. Obviously, because regenerative braking isn’t perfectly efficient, stop-and-go traffic is still less optimal than steady-state cruising at low speeds, and high temperatures are less optimal than low ones since the car’s active thermal management will have to work harder to keep the cells where they want to be (which is about the same temperature as humans — speaking of, all of us in the car were boiling when driving in the valley). Still, this was a good test of the i3’s capability.

The trip began with the i3’s Guess-O-Meter estimating a range of 98 miles in Eco Pro + mode, which dulls the car’s acceleration, limits its top speed to 56 MPH, and shuts off access to air conditioning or heated seats.

Somehow, I convinced my two friends Jeb and Giulia to join me on this rather hot adventure; I even put down towels so they wouldn’t sweat on my i3’s wool seats, which are extremely hard to clean. Notice how, after driving just 14 miles in the city, the computer recalculated its expected range: It expected the car to manage another 96 miles, for a total of 110 miles!

The range estimates on the Guess-O-Meter moved around a lot, as the car recalculated how it expected me to drive based on my pedal inputs. Going up a steep grade made it think I was going to continue driving like a jack-hole, so it dropped the range estimate. Coming back down the steep grade made it think I was going to keep driving like a grandpa, so the range estimate went up. The highest total range estimate we saw was 113 miles. My goal was to hit 100, so this seemed like decent margin.

I drove Jeb and Giulia around the valley a bit, then to Santa Monica on the coast, where, mercifully (especially for Giulia, who has no window to roll down — that’s right, the i3’s rears don’t go down!), the temperatures dropped.

From Santa Monica, I headed to Topanga Canyon, which maybe wasn’t the most efficient move, but I was careful. The i3 was a lot of fun to throw around turns; its tire are skinny, but it’s a lightweight(ish) car, and a BMW:

Eventually, as the distance climbed, and we entered our fourth hour trying to exhaust the i3’s battery (something that would have been very quick to do if it’s maximum efficiency occurred on the highway) our GoPro batteries started to die, as Chris — Galpin’s incredibly talented director — is explaining below:

Darkness fell, which gave us all a break from the terror of that bright yellow ball in the sky, but now I was running late for a commitment I had made, and Chris was growing tired, too. This was a Friday night; the weekend had begun, and we were driving around in traffic for hours on end with dying GoPro batteries and full memory cards!

Jeb and Giulia were kind and patient, Chris and I were the former but less so the latter. Here’s me pointing out how the expected mileage left increased from 37 to 38 while just sitting at a stop light. This was maddening:

Eventually, it was 8 P.M., I was in a bit of hot water regarding my commitment, and Chris was done. So he and talented cameraman Carlo both ditched us. Here they are speeding away, disgusted by the longevity of my BMW i3’s battery:

Jeb, Giulia, and I met up with the person to whom I’d made my commitment, and after apologizing, we had dinner. Then we went home, and I continued testing the following morning, when it was really, really hot near my Studio City Apartment:

As you can see, I started the day having put 89 miles on the battery pack — well above the EPA-rated 72 miles! But I wanted to hit 100, and with only 13 miles on the Guess-O-Meter, I all of a sudden had almost no margin.

So I drove slowly on my way to an EV car show at California State University at Northridge. It was 16 miles away, so I wasn’t expecting to make that. But 100 miles? Surely, right? I mean, the Guess-O-Meter had told me 113 at one point, and was regularly estimating over 105 pretty much all the previous day! Now I had an estimated 102 miles of overall range, and yet, no matter how slowly and carefully I drove, the estimated remaining range seemed to drop more quickly than the miles traveled rose.

My heart started beating fast. “Come on. How?! We had this!” I exclaimed, lightly pressing on the rightmost pedal with my big toe. “100 Miles was in the bag!” No matter what, every mile I drove took more than a mile away from the Guess-O-Meters range estimate. I tried slowing down, but nothing changed! Then my range dropped to four miles after having driven 95.8 miles. That’s a total of 99.8 miles. “No!!!” I continued exclaiming while staring at the Guess-O-Meter like a hawk. Then it happened:

The estimated remaining range dropped from four miles to zero. And in short order: “Popopopopopopo” the gasoline range-extender under my rear floor fired up. The test was over:

I’d driven 96.7 miles, or 24.7 miles more than the EPA’s rated all-electric range, and 10 miles more than I’d gotten out the battery in my previous test. Though I didn’t hit my target, it was a clear indicator that my battery was healthy, and that indeed, paying just $10,500 for this high-mileage i3 with a beautiful interior was the deal of the century. All thanks to one California emissions/consumer-protection law.

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