Toyota Continues Open Technical Discussions on PHEV Designs
- Irv Miller, Toyota's Group Vice President,
Corporate Communications, continues to encourage
broad discussions with the communities of PHEV
and V2G advocates as well as those interested in
automotive engineering. Here Miller's reference
to our responses prompted us and others to
continue the discussion. Below is Miller's posting and our response.
Toyota Open Road: September 24, 2007 06:56 AM
IRV'S SHEET: Hybrid Tech: You Comment, We Respond
Back on September 8th, I published a quick piece
I called "Hybrid Tech: Parallel vs. Series." One
of the great things about the blogosphere is that
it's a two-way street, a format that invites, if
you will, call and response, point and counterpoint.
So it wasn't long until our friends at
CalCars.org (or, more formally, California Cars
Initiative for Plug-in Hybrids), to respond to my
post with some interesting points. If you haven't
already done so, you can read them by scrolling
down to the comments section of my September 8 post.
While we're pleased that the folks there are
willing to engage in this important discussion,
our general reaction to those comments is that
unlike the Blue Ray-vs-HD/DVD metaphor that some
have suggested, we don't see the
series-vs-parallel discussion as an either/or
sort of thing. We do not believe that only one
solution will be adopted, and all others will be abandoned.
Instead, what we expect is a diversity of
solutions. That makes this a very exciting time
for anyone who is interested in advancing
automobile technology. Just as is the case with
conventional internal-combustion engines, we
expect to see many different approaches and nuances.
In any case, it seems appropriate for me to
clarify a few things, so here goes. . .
First of all, it is asserted that existing Nickel
Metal Hydride (NiMH) batteries similar to those
used so successfully by Toyota's Hybrid Synergy
Drive (HSD) system could drive the Chevrolet Volt
(a hybrid prototype that was shown at the Detroit
Show in January) 20 miles electrically without
any change in the Volt's weight or other
parameters if they were designed for what's
called deep discharge. Currently, with most NiMH
batteries, deep discharge is problematic because
the deeper the discharge, the shorter the battery
life. And obviously longer life is preferable to shorter life.
Anyway, the CalCars comments point out that that
20-mile figure is double the 10-mile EV range
that Volt prototypes reportedly will have and
importantly, they attribute that range claim to Toyota.
First and foremost, that 10-mile range is not our
claim. That was published in a story written by
Jeff Green and Alan Ohnsman in Bloomberg.com on
August 3, and published again on GM-Volt.com.
That story cited unattributed information from
inside General Motors saying that the Volt
prototype will have a range of 10 miles. So that
range figure appears to be right from the General's mouth.
Just for the record, here, we have no idea what's
going on inside General Motors, and further, have
nothing to gain by downplaying their successes,
and their advances, with hybrid technology. In
point of fact, we wish them the best, because we
believe that everybody benefits from hybrids, and
from hybrid research and technology.
With that being said, let us be sure that we all
are talking with reference to the same set of
definitions. Honda's hybrid, for instance, isn't
a series hybrid system. It's a parallel hybrid
system. Our Hybrid Synergy Drive system isn't a
parallel hybrid system. It's a series/parallel
hybrid system. The difference is the Honda system
doesn't have an EV mode (series), but ours does.
Likewise, the Volt doesn't have a traditional
powertrain mode (parallel), but ours does.
Now, here's the deal:
Do we favor NiMH technology? Of course we do.
Toyota is heavily invested in NiMH battery
technology. In fact, we think we've probably
produced more hybrids using NiMH batteries than
all other manufactures combined.
But because of our deep experience with NiMH
technology, we also recognize the limits of these
batteries with respect to cost, size, weight,
recycling and life under wide state-of-charge
swings. That is why we're developing new Lithium Ion technology.
In theory, of course a series hybrid could be
developed that pulled a 20- mile range from NiMH
batteries. But it would have to be a
purpose-built car that depended upon technology
that's not applicable to other products.
Meanwhile, Toyota's HSD can be applied, and is
being applied, across our entire product range.
But there's more that needs to be said about this
business of battery-only driving range and
forgive me, here, but this will require some engineering talk.
When range is discussed, it's important to also
consider more than just the traction load. We
also need to consider non-traction electric loads, AKA "hotel loads."
In many, if not most cases, at low speeds, the
"hotel load" (and for you non-technoids, "hotel
load" basically means the power demand from
devices that are necessary or that are demanded
by consumers, but that are not part of the
powertrain that propels the vehicle), can be
higher than the traction load. And as the
automobile becomes increasingly electrified
(steer by wire, brake by wire, heat pumps, active
suspension, etc.), the "hotel load" will require
considerably more battery energy.
Toyota thinks that it's important to let our
customers know what they can realistically expect
to experience in the future. Sure, it's possible
for Car A to get a 20-mile electric range when
driven at low speed with the air conditioning,
lights and stereo turned off. But that obviously
is not how the average person drives. When we
factor in high-speed driving, use of the
air-conditioning system, the audio system and so
forth, Car A's actual all-electric range will be
quite a bit less than that 20-mile grail.
But what's more important here is that this
discussion about the efficiency of one approach
over another is, we believe, misplaced. What's
important is not the specific efficiency of a
battery vs. a transmission. What's important is
the overall package, its acceptance by customers
and the product's contribution to sustainable mobility.
The market for vehicles in the U.S. is around 17
million cars and trucks a year. In order to make
a substantial reduction on our environmental
footprint, the automobile industry needs products
that can go to market today, be affordable, sell
in large volumes, be easily serviceable and be
capable of operating within the parameters of
standard vehicle warranties. At Toyota, with
Hybrid Synergy Drive, that's exactly what we're doing.
[POSTS BY OTHER PEOPLE AT
We at CalCars.org are encouraged and energized by
the continuing dialogue. We agree that everyone
benefits by discussions of hybrid research and technology.
We've asked Ron Gremban, our Technology Lead, to
respond to some of the technical issues you just
raised. (To keep it short, we don't address everything!)
Ron wanted to be sure to start by saying that
"since its introduction, I have been in awe of
the engineering that went into the '04+ Prius and
Toyota's Hybrid Synergy Drive." (And in his Sept
13 response, he attributed the 10-mile Volt
prototype range information to Toyota only
because we hadn't seen the previous news reports
on which the comment was based.) Ron continues:
I agree wholeheartedly that series, parallel, and
series/parallel hybrids and PHEVs will co-exist
for some time in the marketplace, if not from now
on. No single configuration has all the advantages.
Part of Toyota's strong experience with NiMH
batteries comes from the deep-discharge
1990s-technology NiMH packs used in Toyota's RAV4
EVs, some of which by now have well over 100,000
miles on them without significant battery
degradation. In fact, the Electric Power Research
Institute (EPRI)'s prediction that NiMH and
Li-ion batteries can both last the life of a PHEV
is based on that field data as well as its
PHEV-specific laboratory testing. Yes, cycle life
of any battery is reduced with deeper discharge.
This merely means that the engineering tradeoffs
between pack size, depth of discharge, cycle
life, power handling capabilities, etc. must be
chosen carefully, using both engineering and economic expertise.
"Hotel loads" must be supplied, if not from a
battery, from gasoline at the internal combustion
engine (ICE)'s same 15-35% efficiency as
available to propel the vehicle. Therefore, all
the advantages of using grid electricity to
propel the vehicle apply equally to using grid
electricity to supply hotel loads. Even when this
energy provides less EV range in cold or hot
weather use, it is still displacing the same
amount of gasoline (or more, since electric A/C
compressors are far more efficient than
engine-driven ones). The one exception is cabin
heating, which is normally supplied from ICE
waste heat. When it is too cold for an air
conditioning heat pump to efficiently heat the
cabin, EV purity can be sacrificed (independent
of hybrid type) by running the ICE occasionally
to build up sufficient waste heat for cabin
heating. ICEs produce so much waste heat that
mere occasional operation will be quite sufficient.
Plus a final note from Felix Kramer, returning to
a less technical perspective: We agree with Irv
Miller's description of the attributes of cars
that can sell in the millions. But we suggest a
way to get there most rapidly, reflecting the
urgency of climate crisis and fossil fuel
dependency, is by producing (and selling in
surprisingly substantial numbers) "good enough to
start Version 1.0" PHEVs from which automakers
will all learn. Remember the first cellphones:
brick-sized and costing in the thousands? We're
glad the manufacturers started producing them to
continue improving them while scaling up production.
-- Felix Kramer, Founder, The California Cars Initiative 05:45 PM
You can also find comments (some of which overlap
with ones at Open Road blog, and some of which aren't all that polite!) at
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Felix Kramer fkramer@...
Founder California Cars Initiative
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