Aftermarket PHEV conversions at Google and Seattle aren't delivering what was promised. To be sure, there's a number of problems with the "lab" settings. These are aftermarket conversions likely driven by a number of different people with different driving habits and differently weighted feet.

http://seattletimes.nwsource.com/htm...3_danny22.html
http://blog.seattletimes.nwsource.co...n_hybrids.html
http://seattletimes.nwsource.com/ABP...2008768175.pdf

 

Quite right and I would recommend reading:

"PHEV Battery Requirements" by Rousseau, Pagerit, and Fellah, Argonnne Labs, Dec. 3, 2008

Their conclusions, pp. 18

• "Aggressive driving will put limits on all EV range, which in turn favors a blended mode operational strategy."
• Battery size is critical for the expected range
• Aggressive driving results in larger energy requirements

What this means is a PHEV probably won't work in fleet usage where the daily utilization is much greater than just commuting. For commuters, it can be wonderful, but if tried with a taxi cab, the results would be humbling.

BTW, this is one of the reasons the Ford Fusion EV mode up to 47 mph is such a great thing. Although only 5 mph faster than the Prius EV mode, 42 mph, or the ~32 mph in some reports of the "EV" switch mode, it significantly expands the range of speeds the extra battery power can be used.

It comes down that the optimum PHEV appears to be based around:

1. ultracapcitor - low total energy but very fast and high surge. This could also be a fairly small, hydraulic system.
2. NiMH rapid battery - storage capacity needed to deal with the 50-70 kW surge power needed for modest hills, acceleration and regenerative braking.
3. deep discharge - battery designed for energy storage with more of a sustaining load capacity rather than acceleration and regenerative braking

Bob Wilson

 

What the media reported should not be a projection of the future. For example, the "production" fleet Ford Escape PHEV Hybrids (22 have been built and are in real world testing) have a 10kWh lithium-ion battery capacity while the Seattle article referred to an eight kWh battery. Further more, the vehicles shown in the article are from the 2005-07 era and do not have the latest software and hardware changes. Think evolution for the future.