The Truth About Cars » running out of juice http://www.thetruthaboutcars.com The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Thu, 14 Aug 2014 16:30:29 +0000 en-US hourly 1 http://wordpress.org/?v=3.9.2 The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars no The Truth About Cars editors@ttac.com editors@ttac.com (The Truth About Cars) 2006-2009 The Truth About Cars The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars » running out of juice http://www.thetruthaboutcars.com/wp-content/themes/ttac-theme/images/logo.gif http://www.thetruthaboutcars.com EV Range High Anxiety: Normal Driving May Cut Range In Half http://www.thetruthaboutcars.com/2009/12/ev-range-high-anxiety-normal-driving-may-cut-range-in-half/ http://www.thetruthaboutcars.com/2009/12/ev-range-high-anxiety-normal-driving-may-cut-range-in-half/#comments Fri, 18 Dec 2009 15:49:36 +0000 http://www.thetruthaboutcars.com/?p=339584 Would you set out for a drive with your low fuel light on, knowing there was no place to buy gas? That’s the painful reality many EV drivers are going to be faced with every morning after unplugging their fully-charged battery and heading out on the road. Most conventional cars have about 50 to 60 […]

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starting out on empty

Would you set out for a drive with your low fuel light on, knowing there was no place to buy gas? That’s the painful reality many EV drivers are going to be faced with every morning after unplugging their fully-charged battery and heading out on the road. Most conventional cars have about 50 to 60 miles left after the gauge hits empty, plenty of time to find a gas station. But according to a Consumer Reports test of a Mitsubishi i-MIEV, the stated range of 100 miles with a full battery is more like 60 or 50 under typical conditions, if you consider using lights at night, indulging in heat or A/C, or driving at 65 mph typical. I do. And so will most drivers. Disappointment with their $40k electric mini-car is inevitable. Just don’t say Darryl Siry or I didn’t warn you:

I wrote about the potentially misleading and confusing issue of EV range here, and former Tesla exec Darryl Siry has gone public with his concerns of EV makers’ unrealistic claims here, and more specifically, he took Nissan’s 100 mile claim for the Leaf to task here. The problem is well understood by EVers, but not at all so well by the public. Here’s the sixty second capsule version explanation:

IC engines operate at very low efficiency levels, from effectively zero% at a stop light, to maybe in the teens or low twenties at high speeds. We’re used to getting better mileage (range) on the freeway than in the city. But the amount of actual energy required to propel the car is much higher at speed; this is masked by the improved efficiency of the gas engine at those higher speeds.

An electric motor operates at close to 90% efficiency pretty much all the time, so there is essentially a direct correlation to the energy required to move the car, and the mileage (range). And since EV’s use no energy at a standstill (if the heat, lights and radio are off, as in the tests), city driving patterns are dramatically more favorable to EVs.

That explains why EV makers like Nissan and Mitsubishi are using the EPA City”, or “UDDS” driving cycle. This test cycle assumes an average driving speed of 19.59 mph and in the 22 minute driving cycle, it assumes you only break 40 mph once, for about 100 seconds, and never exceed about 58 mph. Not exactly a typical commute from the ‘burbs.

If the EV manufacturers used the US06 driving cycle, which more closely resembles typical US driving patterns, the projected range would be significantly less. But that wouldn’t look good in all the PR and ads. We’ve said it before and we’ll say it again: EVs potentially make great city cars. But head out on the highway, and you’ll be looking for an adventure all too soon.

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