2015 BMW i3 at 105miles range

Is BMW Readying a Longer-Range i3 Electric Car? Sources Say Yes — But Do The Sums Add Up?

Earlier this fall, after months of rumors suggesting it would do so, Nissan announced it would bring the 2016 LEAF electric car to market with an optional 30 kilowatt-hour battery pack, extending the range of the popular plug-in car from the 84-miles of EPA-approved range of last year’s model to 107 miles per charge.

The BMW i3 is rumored to be getting a longer-range battery very soon.

The BMW i3 is rumored to be getting a longer-range battery very soon.

The new battery pack, more energy dense and thus capable of storing more energy per unit mass than its predecessor, catapulted the Nissan LEAF to the top of the range charts for sub $40,000 electric cars, beating cars like the BMW i3 and Kia Soul EV to the top space.

Now, it seems like BMW could be preparing to follow in Nissan’s tire tracks, with the news from UK magazine Autocar that BMW is readying a new, next-generation battery pack which could extend the range of the i3 to “well over 124 miles” per charge in real-world conditions.

It’s not the first we’ve heard of this particular rumor. Indeed, just last month, German language newspaper Zeit said BMW CEO Harald Krüger had confirmed BMW would extend the range of the i3 electric car upwards from its current 81 miles of EPA-approved range for the 2017 model year. At the time, Krüger didn’t discuss specifics, but talking to Automotive News Europe earlier this year, the BMW CEO had promised the brand would improve the energy density (and thus range) of the BMW i3 electric car and BMW i8 plug-in hybrid sports car battery packs by a minimum of 20 percent every three years.

The lightweight construction of the BMW i3 helps it achieve incredible efficiency.

The lightweight construction of the BMW i3 helps it achieve incredible efficiency.

So far, so good. But while the rumor from Autocar does seem to back up similar rumors we’ve already heard, there’s something in the reporting which has already got some enthusiasts a little confused.

You see, while Autocar reports anonymous sources within the automakers claiming BMW has a brand-new, next-generation battery pack in development, it also reports no change in battery pack capacity — the usual way in which automakers increase electric car range.

“The i3 will receive a new lithium ion battery with the same 22kWh (18.7kWh usable) capacity as that used today but a higher power density for a longer range,” the publication states. But while it uses the term ‘power density,’ we think it means energy density instead.

That’s because power density is the measurement of how much instantaneous power a battery can provide per unit mass (or volume). A battery with a high power density is capable of moving energy into and out of the battery more quickly than a battery with a low power density. Energy density meanwhile is the measurement for how much energy can be stored per unit mass (or unit volume).

Capacity meanwhile, is how much electrical energy a battery is capable of storing, measured in kilowatt-hours. A high energy density battery can store more electrical charge per unit volume than a low energy density battery pack.

The same battery pack capacity but less on-board weight would mean longer range.

The same battery pack capacity but less on-board weight would mean longer range.

Here’s where we think it might get confusing.

In the world of electric cars, we’ve got used to the idea that improvements in battery chemistry mean that automakers automatically increase an electric car battery pack’s range by using a more energy-dense battery cell chemistry in the same physical battery pack space as its predecessor. So far, we’ve seen just that happen with the Nissan LEAF, the Tesla Model S (multiple times) and both the Chevrolet Volt and Chevrolet Spark EV.

In each case, range has been increased slightly, with the higher-capacity battery pack taking up the same physical space inside the vehicle as previous-generation packs.

But battery pack capacity isn’t the only way to increase range. Saving weight can help, too. And if a next-generation battery pack is lighter than its predecessor, it will save energy.

That’s something that BMW knows only too well. Indeed, both the BMW i3 and BMW i8 have class-leading efficiencies, thanks to the use of lightweight carbon-fiber reinforced plastic (CFRP) for body panels and lightweight aluminum chassis replacing traditional steel ones. Thanks to the wonderful laws of physics, the less weight there is to push down the road, the less energy you need to move it.

Which brings us nicely to our theory. While we think the Autocar report may have confused the terms power density and energy density, we certainly wouldn’t be surprised to see the BMW i3 gain extra range from a more energy-dense, more lightweight pack. Given BMW’s focus on efficiency rather than simply building an electric vehicle with zero tailpipe emissions, this rumor (taken in the context above) does make sense.

There are advantages to this method over simply using a larger pack, too. With an identical battery pack capacity but far more energy-efficient drivetrain, BMW ensures running costs stay the same for customers, as well as charging times for standard Level 2 charging. Combine a more energy dense pack with a more power dense pack — in other words a pack which can store more energy per unit volume than its predecessors but also transfer energy more easily than its predecessors — and you have a double-whammy: a battery which offers fast recharge times and low running costs.

While we can’t say for sure that’s what BMW is planning, that explanation fits better than anything else we’ve thought of. Do you agree? Leave your thoughts in the Comments below.


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  • Janner

    Today’s i3 battery has an energy density of 95whrs/kg giving 80 miles range (EPA). If BMW follow Samsung’s development roadmap then in 2016 energy density will be 130Whrs/kg – 110miles, followed by 210 miles in 2019 when bettery energy density is expected to be 250WHrs/kg.

    However, the BMW i3 brochure in the UK has the range of the existing car as 118 miles (NEDC) – If the Autocar announcement is on the same basis then a range increase from 118 to 124miles (5%) could easily come from some minor tweaking without changing anything much in the battery – most probably just by opening up the usable battery from 18.8 out of the nominal 22kWHrs to 19.75, something many have already seen in various recent software updates.

    • Aldo

      I don’t know the uk spec on the i3, but in SA, you get on the road of about 120km on a full charge, so the 80mile seems more realistic to me. However, we are eagerly awaiting more news on the new batteries, as that will do a lot to ease range anxiety, which is still a big thing on the southern tip of Africa, as our charging infrastructure is basically non existent. I hope for that to change sooner rather than later, as we don’t get tax deductions for buying electric, the range issue is a biggy for us.

  • No way BMW can increase range by 50% without increasing battery capacity. That would demand a 30% lower energy consumption.

    How? By shaving perhaps 50 kg of weight from the battery? You can never save 30% energy with a 5% weight reduction. Reducing drag? Maybe if you completely redesign the body from scratch to make it look like the VW xl1. Improving the drivetrain that is probably already close to 90%?

    So my guess is that the reporter simply has no grasp of the subject. Someone has probably said the battery is the same size and more energy dense. “Size” in this case meaning physical dimensions, but the reporter must have thought that “size” referred to capacity. And this whole thing of power and energy, that is >90% of the population that can’t tell the difference. So I’m sure that instead of the “power density”, Autocar should have written that “energy density” will improve.

    Boy, it must be hard for those petrolheads to learn new stuff.

  • Sad effort by BMW in my opinion. While their i3 is an efficient car in terms of the energy needed for locomotion, they completely do not understand that those of us in Northern places.

    In climates (like Ontario Canada) where we get cold temperatures for 1/3 of the year, the only solution for longer range is a larger battery pack.

    Greater efficiency doesn’t matter much at all if you are consuming 4 kW to heat the cabin and defrost the windows.

    My Smart ED gets the exact same efficiency in the winter as our Tesla Model S in city driving, even though the Tesla is much heavier. The reason is that it takes about the same energy to defrost the wind-shield in both cars, and that energy usage is a goodly percentage compared to the energy needed to get the car moving.

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