People are used to driving their cars long after the empty light turns on – most people could even tell you exactly how many miles they can go before their tank completely runs dry.  The idea of charging up a car instead of filling up is foreign to most people, so it’s natural to be concerned about what happens in an electric car when the juice runs out.

These concerns are understandable, but running out of charge in a CODA is very similar to running out of gas in a gas-engine car.  In both instances there are many warning signs before the car’s wheels stop rolling.

The CODA is engineered to maximize the life of the battery by not fully draining the battery every drive cycle.  However, if you are in a situation where you simply forgot to recharge, the CODA has a system in place to maximize range (miles per charge) as the state of charge (SOC) nears zero.

When the CODA gets to about 15% SOC, a three-stage, orderly reduction of power begins which helps to maximize range and avoid high power draws from the nearly empty battery.  In the first stage, the driver can continue driving at maximum speed (80 mph) but acceleration is limited, meaning the car may feel a bit sluggish when trying to speed up.  In the second stage, acceleration and power are limited, allowing a top speed of ~60 mph.  In the third and final stage, acceleration and power are limited, allowing a top speed of ~35 mph.

With each stage lasting ~5 miles, the driver has ~15 miles to get out of traffic and pull over to safety.  At each stage, the CODA’s telematics and in-dash screen alerts will help to indicate to the driver that they should pull over.  The moral of the story is that drivers should plug-in regularly to avoid this situation, but they do forget there is ample time to find a suitable place to pull off to the side of the road.

Maybe Nissan and GM are still talking in MPG because that’s all they know, but the EPA and NHTSA are also partly to blame for the confusion.  The first problem is that consumers are accustomed to gauging efficiency in MPG, so the big auto makers and the EPA are inclined to rate fuel economy of electric vehicles using a MPG equivalency figure.  The second problem is that since car companies must comply with strict Corporate Average Fuel Economy (CAFE) regulations set forth by NHTSA, electric vehicles must also have some sort of MPG value applied to them for the purposes of calculating regulatory compliance.  Consequently, the resulting calculations and policies have more to do with politics and influence that any basis in science.

In fact, under the current CAFE rules, the MPG equivalency of an electric car is calculated assuming about ~82kWh of energy per gallon of gas, when the actual energy content of a gallon of gasoline is about 34kWh. Meaning, the CAFE regulations have essentially changed the law of physics to artificially enhance MPG for electric cars, and all to give manufacturers a boost to comply with the regulations.

We get that fuel economy is one of the biggest factors when people buy a new car. It’s such a big deal that according to a Pike Research study, 85% of respondents said that improved fuel efficiency will be an important factor in their next vehicle purchase. But, we also think that MPG equivalency ratings aren’t an honest way to communicate electric car fuel economy to consumers.   To us, it’s like comparing apples to oranges.

The efficiency of an electric vehicle has nothing to do with gallons of gasoline, so why are we still talking in miles per gallon?  Using the EPA’s approach for the Chevy Volt fuel efficiency rating, the CODA electric car would have iMPG – infinite miles per gallon – because it doesn’t use ANY gallons of gasoline.  So while EPA fuel economy ratings can give consumers a way to compare the efficiency of one vehicle to another, when the calculations are driven by politics and influence rather than hard science MPG equivalencies only confuse consumers more.

At CODA, we believe the best way to measure efficiency of an all-electric vehicle is by calculating the amount of energy used per mile (watt hours per mile.) This also gives consumers an accurate way to compare different electric vehicles side by side.  We think the issue is confusing enough and that we shouldn’t be trying to compare electric cars to internal combustion cars when it is obvious that they are completely different.

As for plug-in vehicles that have some amount of “all-electric range” but also use an internal combustion engine either in parallel (Toyota Prius) or in serial (Chevy Volt or Fisker Karma), a new approach is needed. Plug-in hybrid vehicles should be rated on “electricity per mile” for the all-electric component and traditional MPG for when the engine is running. Both ratings should be shown on fuel-economy stickers.

Now that’s more like apples to apples.

Not surprisingly, this problem can be traced back to internal combustion cars.  Do you actually get the MPG promised by the EPA on the window sticker when you bought your car?  We don’t either.  Fortunately for you, and everyone else who’s not driving like my grandma or our cautious product engineer, gas stations are easily accessible, so it’s not really that big of a deal.  Most drivers know that the “EPA City” and “EPA Highway” mileage ratings are only an estimate of what they should expect when they buy a new car, not a daily guide of when to refill their tank.

The problem is that many companies coming out with an electric vehicle are communicating a single range number.  Sometimes it’s based on a combination of the EPA City and the EPA Highway driving tests, and sometimes it’s only based on the EPA City test; neither one gives consumers a realistic range expectation.  And since there aren’t yet readily accessible fast charge stations to plug into when your car runs out of juice, range is a critical piece of information that drivers of electric cars need to plan around.

The EPA City test (aka UDDS or LA 4 cycle) creates the best possible scenario for optimizing EV range, with a very low average speed of 21.2 mph and lots of stops and starts resulting in low aero drag and maximizing the benefit of regenerative braking.  While it isn’t false to claim that a vehicle gets 100 miles per charge based on the EPA City test, it seems misleading to tell consumers they can normally expect this many miles per charge considering most people drive faster than 21 mph throughout the day.

The EPA Highway test is more representative of the actual range drivers should get in an electric car.  With a top speed of only 60 mph, slow maximum acceleration (3.2 mph/sec) and no stops, the Highway test still doesn’t accurately represent the way people typically drive.   Who really tops out the speedometer at 60 mph on the freeway?

That’s why we believe the EPA City test and the EPA Highway tests don’t cut it.   From our perspective, another test, the EPA US 06 (aka aggressive driving or high speed test), is far more representative of the way average drivers actually drive.  Not only does the US 06 test have a top speed of 80 mph and average speed of 48.4 mph, but it also has higher maximum acceleration of 8.46 mph/sec than the other tests and includes stop and go situations.  We believe this is currently the most representative test to measure expected range.

In lieu of developing an EV specific test, CODA Automotive believes that the DOT should require reporting and labeling of the US 06 range along with the EPA City range to represent a reasonable lower and upper range estimate for daily driving.  In the meantime, we urge all manufacturers to voluntarily communicate both the US 06 and the EPA City numbers and for the media to report US 06 numbers so that people begin to understand that electric range can vary significantly depending on how they drive.

This is what CODA has done all along. We usually say our car will go 90-120 miles per charge. When we say this, we are using the modeling estimate for our range under US 06 and UDDS (we will confirm these numbers using our production models). When we need to use a quicker sound-bite, we say “over 100 miles” to err on the conservative side.  We think that’s the best way to communicate such a critical issue to the public.