Simonsen, John wrote:
> Like most people, I am quite impressed with the technological
> achievement of Ewert Engineering and I hope their business is wildly
> successful. The thing that bothers me, though, is that when I watched
> the video, the % charge of the battery dropped drastically over the
> ten minutes or so of the video. It appeared to me that using their all
> electric high speed drive one would have to stop and recharge in less
> than an hour, or else use the ICE, just like a stock Prius. Am I wrong
> on this?

You are correct, the Prius will use energy faster at higher speeds. If
you go twice the speed, the car is traveling twice the distance in the
same amount of time and therefore uses (at least) twice the amount of
energy. That part balances out and you are using similar amounts of
energy per mile. However, at higher speeds, the car experiences more
wind resistance as well as more loss from the battery since energy is
being pulled from it faster. Wind resistance grows exponentially with
speed and is actually pretty considerable at speeds > 50mph. In the
end, a battery that could do around 25 miles for low speed driving,
might do 17-20 miles on the highway (or less at very high speeds
(>70mph.) For this reason, if you are doing a long highway trip, the
best place to use the electric drive is for lower speed driving and to
use the gasoline engine for highway driving. The system has an input
for the length of the trip and if you drive with the enhanced PHEV mode,
it will automatically optimize the driving profile for best fuel economy
over the entire trip and will automatically switch between mixed mode
and electric mode depending on what is most efficient for the specific
drive.

In response to the comments about making this available for CalCars
conversions: Our goal is and always has been to prove that this
technology is available today and to make it available to anyone who
wants it in such a manner that it promotes the use of plug-in hybrids.
We have been strong supporters of the open source movement and believe
strongly in it. We have been proud to be a part of it as it played it's
role in publicizing plug-in hybrids, but we have also watched with
concern both when incidents have occurred in converted cars and when
conversions failed to live up to their expectations. We believe it is
important that conversions be done correctly and demonstrate the full
potential of plug-in hybrids such that they are not written off by
consumers as unsafe or unreliable. Due to the increased power required
for the enhanced modes and far more complex systems, professional design
becomes even more important than it has been in the past. Because of
this, we found it necessary to take the commercial route such that we
could invest more heavily in safety and making sure this is done right.
We picked Plug-In Conversions to work with both because they have a
system capable of powering the mode and have also demonstrated a level
of professionalism and concern for safety.

I should stress that from a technical perspective, this enhanced
electric mode is incompatible with a CalCars style / contactor based
conversion for a number of reasons. Plug-In Conversions newest system
is a completely different style of conversion, replacing the OEM battery
instead of adding an additional battery. This route eliminates many
issues that add on pack conversions suffer from.

Chris



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