Volt Misses Another Goal: Battery To Discharge Deeper Than Planned

Paul Niedermeyer
by Paul Niedermeyer

Although the finished product works well enough, it’s also becoming increasingly apparent that the Volt missed two key project goals. GM’s oft-stated promise that the Volt would achieve 50 mpg in CS mode is history. The fact that GM felt the need to optimize the fuel consumption of the Volt by using premium (required, not just recommended) indicates how rather inefficiently its serial-predominant hybrid system works. It’s not a matter of ragging on about that; it’s just a surprise to those of us who argued endlessly which system (serial or parallel) was more efficient.

And now another long held Volt assumption is deflated. Based on GM statements made during the Volt’s long development, the universal understanding was that the Volt would use 8 Kwh of its 16 Kwh battery pack to achieve its 40 mile AER goal. It now turns out that 10.4 Kwh will be utilized. Sounds like small potatoes, but there are three not insignificant consequences as a result:

The very immediate and obvious one is that it will take more electricity to recharge the Volt. Given the losses of conversion at the charger and in the battery, it will probably take 12 to 13 Kwh of metered electricity to recharge a depleted Volt battery, so that the electric “fuel” costs in calculating the Volt’s operating costs need to be increased by some 20%-25%.

The more serious issue is that this deeper rate of discharge will stress the battery to a greater degree. Unsurprisingly, GM says, and presumably believes, that this is not a significant issue, and has confidence in the battery’s long-term health over its projected life. GM has said that the battery will lose between 10% to 30% of its capacity during the 8 years/100k miles of the warranty period. Whether the consumer or GM are hurt more if the Volt battery eventually turns out to age more rapidly is unknown, but it does increase the odds of there being an impact as a result of the deeper discharge.

Why was this change made? The Volt wouldn’t have met its nominal 40 mile AER without it. This and the Volt’s lower gasoline economy are interrelated. Both early Volt goals (40 mile AER on 8Kwh and 50 mpg in CS mode) were not met, because the Volt turned out to be less efficient in both modes.

Whether that’s the fault of excessive weight (some 3800 lbs), or less-than sterling aerodynamics (Cd: .28, same as a W124 Mercedes of 25 years ago), or other inefficiencies, is not known. Yes, the Volt works, just not as efficiently as hoped for, by both its maker and those that have followed its development.

Paul Niedermeyer
Paul Niedermeyer

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  • Philadlj Philadlj on Oct 27, 2010

    The VW Phaeton was engineered to be capable of being driven all day at 186 mph with an exterior temperature of 122°F whilst maintaining the interior temperature at 72°F. Those were concrete goals that were set - and met - by Volkswagen. Highly-publicized, stat-based promises shouldn't be made casually. If the Volt team had set low, achievable goals and met or exceeded them, they'd be looking a lot better right now. Every promise they break hurts their credibility and loses one or two well-informed customers who were already on the fence.

    • See 1 previous
    • Steven02 Steven02 on Oct 27, 2010

      You sure those were met? Can it drive for 24 hours on its gas tank at 186 mph and 122F? Honestly, that is the type of criticism that people have for the Volt.

  • GarbageMotorsCo. GarbageMotorsCo. on Oct 27, 2010

    Is the Volt going to be backed with a 100 thousand mile warranty? Sure would add a little comfort for those *guinnae pigs living with a brand new design with zero reputation for reliability, quality nor longevity. From Government Motors of all companies. Yikes. *The ones that aren't giving it back after the 36 month lease is up.....

  • MaintenanceCosts It's not a Benz or a Jag / it's a 5-0 with a rag /And I don't wanna brag / but I could never be stag
  • 3-On-The-Tree Son has a 2016 Mustang GT 5.0 and I have a 2009 C6 Corvette LS3 6spd. And on paper they are pretty close.
  • 3-On-The-Tree Same as the Land Cruiser, emissions. I have a 1985 FJ60 Land Cruiser and it’s a beast off-roading.
  • CanadaCraig I would like for this anniversary special to be a bare-bones Plain-Jane model offered in Dynasty Green and Vintage Burgundy.
  • ToolGuy Ford is good at drifting all right... 😉
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