Tag Archives: Ev

EV Advocacy

Those of us early adopters driving EVs tend to evangelize our cars just a little bit. How can you not? Just driving one around for a week or two makes you realize how nice an EV actually is. The quiet and smooth ride, the instant torque, etc. In lots of ways it really does feel like driving the future around (especially since I’ve noticed that the distinctive sound my Focus Electric makes is very similar to the “vehicle noise” you would hear for a car in all those 80s Sci-Fi shows–Battlestar Galactica, Buck Rogers, Quark, Logans Run, etc.).
Currently the biggest “minus” about driving an EV is the state of battery technology: To get an EV the range of a similar ICE vehicle much more volume of the car must be taken up by the battery (sometimes by several factors: 2X, 3X, etc.). Even the Tesla Model S devotes a significant portion of the bottom of the car to the batteries. This will change in the future rather quickly as there are a lot of people doing research into better, higher density, lighter, etc. batteries.
Moving on from the battery, what about the rest of the car? Well what if we compare the drive trains: On a conventional car you have an internal-combustion-engine with many moving parts. With the EPA ratings pushing higher and higher the gas engines of today will be getting more and more complex (adding direct injection, turbo chargers, variable valve timing, Urea injection–for Diesels, etc.). All of these added parts are just more points of failure waiting to happen. Think about it: as a car ages you put more and more effort ($) into the engine to keep it running. An EV’s drive train couldn’t be simpler: One or more electric motors either connected directly to the wheels or through a reduction gear and differential to the wheels. (In the FFE’s case the motor wraps around one of the half-shafts and is connected to a differential through some reduction gears–see this post–there isn’t even a clutch the motor is always turning!) In addition the electric motors used in EVs are either permanent magnet or synchronous motors without brushes–they won’t ever wear out! On an EV as the car ages you’ll find yourself repairing and/or replacing items that you’d never think to in an ICE car: Suspension arms, seats, HVAC fan motors, etc. I bet it will be common to hear about EVs with a million miles on them (with more than one battery swap out).


The “Guess O Meter”

Every EV has one, heck even many ICE cars have one: The “Guess O Meter” (in ICE cars it is called “Distance to Empty” which, unlike EVs, tends to be pretty accurate). I initially heard about the term “Guess O Meter” (GOM) by some Nissan Leaf drivers before I even owned my Focus Electric. The number of miles left in the battery would vary wildly in their cars even, in some cases, within the duration of a single drive!

In short the meter is supposed to give you an accurate representation of how many miles you can go with the charge left in the battery (likewise the ICE version “Distance to Empty” (DTE) is how many miles you can go with the gas left in the tank). On an ICE vehicle the DTE reading is pretty accurate and doesn’t fluctuate much–and rarely, if ever, increases. Not so on an EV. Here is an experiment: Take your EV out on the highway for a few miles and watch the GOM drop precipitously; next, on the same trip, drive slowly around some residential streets for a few minutes and watch the GOM climb and climb.

An extreme case of this: My coworker took his FFE down the Woodward Dream Cruise this past summer where he had to drive it under 10 mph for quite a few miles. His GOM rose and rose and rose topping 200 miles at one point!

Now Green Car Reports has just posted this article about a long range drive with a Tesla Model S and I found this quote rather informative:

I don’t have a lot of faith in the Model S range meter. Its number is a projection based on rule-of-thumb efficiency assumptions, battery temperature, and a safety fudge factor.  (New York Times reporter Jonathan Broder famously fell victim to wildly fluctuating range numbers.) I call it the guess-o-meter.

Well look at that! Even the much praised Tesla Model S’s range meter is as wild as my FFE’s!

From my experience the GOM seems to place too much stock in the most recent driving performance and ignores the longer term average. I would suspect that it would be far more accurate if it simply used the rolling average of the power consumption over the past week or two (instead of appearing to only use the past 20 minutes or so!). Using a longer term rolling average would also make it a bit more stable and not change so drastically (I think this is what gets most people: Drive for a few miles and all of the sudden you are up or down 20 miles).