I was particularly interested in the battery's recharging requirements, in relation to the energy density concerns I discussed in last Tuesday's posting. The Volt recharges in two modes: At 240 V and drawing between 15-30 amps, it takes up to 3 hours to restore the roughly 50% of the battery pack's 16 kWh maximum charge used in "charge-depleting" operation--that first 40 miles or so of battery-only driving that provides the car's main selling point. Recharging on 120 V household current takes more like 8 hours. I was somewhat surprised that Tony seemed to share my view that Volt drivers are unlikely to wait until the middle of the night to recharge their cars, unless their highest priority is minimizing their electricity costs (and possibly emissions.) He has apparently been using a Volt on weekends and cited the benefits of daytime recharging at home or office to keep the battery ready for use, consistent with the main purpose of owning such a car.Moving the US fleet of vehicles from their current 25 mpg to something like 75 mpg would reduce the importation of oil and the amount of CO2 dumped into the atmosphere. I'm not saying this will do it, but obviously technology can move us a long way toward whatever goal we have in mind.
The switchover from battery-only operation to driving with the onboard generator running was one of the key features I was anticipating, based on my concern that the Volt would ultimately be handicapped in low-battery, "charge-sustaining" operation by its reliance on a fairly small 4-cylinder engine. After all, the performance expectations in the category the Volt aspires to are set by powerful engines similar to the V-6 in my Acura TL, which delivers 270 peak horsepower. Well, you could have fooled me. The Volt I drove yesterday was intentionally given just enough battery charge to last about 3 miles, and when I passed that point and the little engine fired up, there was no discernible change in performance. That's apparently because the car is never really driven by the engine alone, since the battery is never completely drained. The accelerator controls only the flow of current from the battery to the electric motor; meanwhile the car's software runs the engine as needed to keep the battery charged to acceptable levels, but not to recharge it fully. That's a subtle distinction, because when I pushed the car hard in this mode, I heard the engine rev up noticeably with that characteristic 4-banger tone that provided the one discordant note in an otherwise near-luxury experience. But the trade-off was evident when I pulled the car into its tent shelter and switched it off. The cumulative fuel economy display on the dash read a whopping 910 mpg.
That result prompted an interesting discussion about what fuel economy really means in a car like this, which dutifully calculated mpg based on the tiny amount of gasoline consumed in the last lap of several miles of mostly battery-powered driving. I got a sense that GM recognizes the shortcomings of mpg in measuring such a vehicle's energy usage, though they are clearly quite focused on it as the primary metric of both consumers and the existing and proposed federal fuel economy standards. But even knowing intellectually that the car's electric efficiency, which Tony confirmed is in the range of 200-250 Watt-hours per mile, or 4-5 miles per kWh, equates to roughly 58-72 miles per gasoline-gallon-equivalent of natural gas going into a gas turbine power plant somewhere, that 910 mpg still got my attention with its implication of very rare visits to the gas station.
I'm so tired of the simple-minded political protestors whose only response to any perceived problem is to ban it or tax it. The option of technology as a tool to fix the future is completely overlooked. It deserves to be the first option not the last option for most of the problems society faces. To my mind, a carrot is a far better tool of social persuasion than a stick.
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