Op-Ed: To SOC or not to SOC – The Future Is Here And It Is Called The BMW i3 Range Assistant
There has been much discussion on the boards recently about BMW not including a State Of Charge(SOC) indicator in the new i3 for the United States model. Many veteran electric vehicle(EV) drivers have expressed major disappointment, their EVs have always had SOCs, some owners going so far as to retrofit third party meters on vehicles not so equipped.
Why would BMW make such a strategic mistake omitting a gauge that is so vital for daily EV use? It is true, SOC is a commonly found indicator on board EVs of all kinds and drivers have come to rely on them heavily to know their range among other things. But how necessary is it on the BMW i3?
Editor’s Note: Our thanks to contributor Darren Schurig (Yiiikes) for putting to together this op-ed
What is it that we really want to know?
Are we going to make it to our next destination?
How far can we go before we need to recharge?
The two critical pieces of information that have created a frenzy of apprehension about EV transportation and engendered use of the expression “range anxiety” due to the lack of a gasoline-like recharging infrastructure. The term first surfaced during the era of the GM EV1. GM went so far as to file for a trademark on the term presumably to use as part of their new plug-in hybrid marketing campaign (their filing was not granted). Much like a fuel gauge in an Internal Combustion Engine(ICE), the SOC is the primary meter used to answer these questions.
The Venerable Dipstick
Early gasoline automobiles did not have fuel gauges, in fact they did not have any instrumentation, the technology did not exist. Fuel level was measured with a dipstick that was inserted into the tank. A dipstick could be calibrated to the shape and volume of the tank or merely measure inches of fuel. The first dash-mounted gas gauge for an automobile was by Studebaker in 1914. Rickenbacker offered the first electrical fuel gauge in 19251. It provided real time information and was more convenient – it was better. Ultimately the automotive fuel dipstick went the way of the dinosaurs. It is still in use today however for light aircraft, industrial applications and more.
What is SOC and how do we use it?
SOC in its most rudimentary form is a measure of the amount of energy stored in a battery just like a fuel gauge tells us how much gas(energy) is left(stored) in our tank. As a metric, it does not directly answer either of the two questions above. Analogous to the fuel gauge of the (ICE) vehicle, we must take it as a starting point to a long series of considerations, all the things that affect how fast the stored energy(fuel) will be depleted – distance, road type, elevation changes and driving style. Using a combination of guesstimates, hunches and intuition as an “algorithm” in our head (try writing it down someday) that we each develop ourselves for our particular EV, we determine the answers to the critical questions above – in the same way we would for an ICE vehicle on a long trip (rarely necessary in urban area trips due to the extensive gasoline refueling infrastructure). In that way, an SOC is a holdover from ICE technology.
The GM EV-1 had an SOC gauge in 1996, 18 years ago. It looked exactly like a digital ICE fuel gauge of the GM products at the time (see fig. 3.6). That was the technology of the day, nothing else existed to aid in the understanding of your energy use profile. But does an EV need to merely be an electric analog of the ICE that has massively overshadowed it all of these years?
The World Changed
The global technology that has been created in the last thirty years is positively transformational. We quite literally could not maintain our daily lives today without most if not all of it.
- Computers-small machines that can reliably perform an unfathomable number of calculations or instructions in the blink of an eye
- Artificial Intelligence-machine learning through regression analysis, decision tree learning, association rule learning etc.
- Cellular Phones –wireless communication with wide geographic coverage
- The Internet/World Wide Web-publically accessible repository of every kind of media and information imaginable
- Global Positioning System (GPS)-a system of satellites and a receiver that can pinpoint our position and elevation on the globe to within 7.8 meters (accuracy of better than 3 meters is possible)3
- Web Mapping Services (Google Maps) – extremely accurate mapping of the physical world with visual imagery of virtually the entire globe. Includes route planning with distance and time to destination
- Smart Automobiles-dozens to hundreds of on board sensors and processors to monitor vehicle conditions and enhance safety and performance – wheel speed, ambient temperature, cabin temperature, engine temperature, accelerator position, yaw, roll, acceleration, steering wheel position, parking (proximity), blind spot , tire pressure, ad infinitum
As an example of how these developments have become indispensible in our lives because they are so much better than the technology they replaced, Goggle Maps makes it possible to know the route, distance and elapsed time to any place in the US in a couple of seconds. And it is accurate to within a tenth of a mile (528 ft). That is substantially faster and far more accurate than paper maps or Thomas Guide or any kind of estimate we could do in our head.
What if . . .
…you could combine all of these remarkable tools, each one life-changing in and of itself, into one solution that could tell you precisely how far you will go with the energy you have on board? And what if it was continuously updated in real time? And presented in a simple to read color graphic? Unimaginable?
Well it is here today and it is called the BMW i3 Range Assistant, the most advanced and sophisticated ranging utility ever developed for a consumer product. Much like the automobile that subsumes it, it is an ingenious combination of the technology that has vastly enhanced and shaped our lives in the last 30 years.
Incorporating all of the technology above, it evaluates battery charge level, driving style, use of electric convenience systems (heating/air conditioning) choice of drive mode, route topography (inclines and declines) and the current traffic situation and generates a very simple to understand map visual on a mini tablet sized display that directly without any interpolation answers the two questions above. It displays the radius of range for each of the three drive modes and clearly indicates whether you will reach your destination or not. You don’t even have to tell it where you want to go. Notice that the range radii are not circles – Range Assistant iterates possible routes from your current position and corrects for range sapping or supplementing factors for each. If your destination is in the shaded area, you will get there, it is that simple.
This information is shown on the dynamic range display in real time which provides an overview of all possible destinations. If a destination is out of reach, the car will suggest going into ECO PRO or ECO PRO+ mode to maximize the vehicle’s range by limiting the top speed and switching the heating / ventilation system into an energy-saving mode. If that still isn’t enough, the car can display public charging stations in the area which can be reserved from the display. A casual glance at the display and you know precisely and directly the answers to the two critical questions. It determines range using more data points, more precise data, and orders of magnitude more accurate calculations than anything we can do in our heads. No guesstimates, no hunches no mystical algorithm. And no range anxiety.
Like the fuel dipstick that was displaced by the better fuel gauge and the paper maps outdated by Google Maps, gone is the tiny seven segment display of esti-mated range and the need for SOC. SOC is as necessary to a BMW i3 with Range Assistant as a fuel dipstick is to a new 535i – obsolete technology.
In 1986, I was on a team in college that designed and built a carbon fiber reinforced polymer(CFRP) monocoque with aluminum component Human Powered Vehicle(HPV), very possibly the first of its kind (pre-preg carbon fiber was $4,000 a lb. at the time). It was utterly beyond our young engineering intuition how a material could be so light and so strong. We second guessed our analysis many times before building it out and competing with it.
Years later I worked for one of the world’s most renowned automotive concept and prototype fabricators and in 1998 we built the first carbon fiber monocoque on aluminum chassis concept car for one of our OEM customers. Again the strength to weight property of the material was mind bending. We went on to build many more that included fuel cell, electric and hybrid drivetrains. It was obvious to us at the time that CFRP would find a place in automotive manufacturing once the problem of mass-productionizing it could be solved. Incidentally several of the designs we built had “coach” or suicide rear doors.
Now 15 years later BMW has made that future a reality for mass production and with it introduced a new transportation paradigm on every level. It is the first automobile I have been excited about since my 2002 BMW M3 and those CFRP on aluminum concepts we built. It ushers in a truly new way to engage in transportation, a culmination of technology and sustainability never before seen.
A Truly New Paradigm
Electric vehicles span a full range of designs from ICE platforms that have been modified in one way or another to accommodate electric drivetrains to purpose built, clean sheet designs that truly leverage the unique opportunities presented by electro-motive drive. Tesla Model S is a great example of a clean sheet design with amazing reliability, luxury and performance. Even it is still an industry standard automobile in its appearance, material and construction, albeit a remarkably good one. Several of my friends/colleagues that worked with me on those original CFRP concept vehicles are engineers at the Tesla engineering studio.
The BMW i3 is truly a new paradigm in automotive language, a clean sheet design that leverages new visual language inside and out and employs new materials and construction that sets a new bar for architecture and weight management. The EV no longer needs to be a copy of an ICE with an electric motor.
Going hand in hand with that paradigm shift is the most accurate and reliable range prediction utility ever made available to the public. It answers very directly the two questions that opened this editorial with a casual glance that can be understood by anybody. No more interpolating and guesstimating and hunching your way to your next destination. A human can never hope to be able to know or account for the fantastic volume of data the Range Assistant incorporates into its prediction, let alone approach the accuracy of its calculation.
Thank you BMW for bringing such a remarkable vehicle to our world. Early adopters unite, embrace the new paradigm in all of its glory including the i3 Range Assistant. Allow an EV to be something completely different than an ICE and bury your need for an SOC with the fuel dipsticks and Thomas Guides!
One final note, another question that an SOC may be useful to help answer – How long will it take to recharge the battery from its current level to full or any other level? BMW i3 has a solution for that too . . .
Darren Schurig (Yiiikes)
History of the Fuel Gauge, http://www.crankshift.com/fuel-gauge/
Measuring Fuel in Early Fords, http://www.post-journal.com/page/content.detail/id/608693/Measuring-Fuel-In-Early-Fords.html
How does GM’s fabled EV1 stack up against the current crop of electrics?, http://www.digitaltrends.com/cars/how-does-gms-fabled-ev1-stack-up-against-the-current-crop-of-electrics/
Performance Characterization, GM EV1 – Southern California Edison, pg. 6