Hybrid Car – More Fun with Less Gas

lith ion batteries for prius? - Page 3

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Posted by e on April 4, 2008, 12:18 am
Hymotion and Edrive currently offer kits that permit a
Prius to be converted to lithium cells and plug-in
charging. It's aftermarket, but the Prius Club reports
many of them on the road - operating successfully.

Toyota's chairman has publicly announced lithium cells
in the 2010 model, to be made available in about a year.
Obviously, to make production by that time all the parts
sources and procedures must already be properly lined up.

I expect 3-4 different lithium-powered cars with plug-in
charging within three years.


Posted by Bob & Holly Wilson on April 4, 2008, 12:22 pm

The only exicting thing I've seen is a GM experiment that put the LiON
batteries in an active, environmental housing. They created an actively
management environment to keep the LiON cells in their 'safe' range but
this of course taxes energy.

Agreed. Although LiON cells have higher energy density, the overhead is
the cells have to be maintained in a benign environment and this takes
active management.

I think there is a perception problem that hybrid performance comes
directly from the batteries. From what I can tell, the batteries are
keeping the ICE in energy efficient modes. This is a much smaller energy
demand than most folks realize.

The Dept. of Energy ran a fleet study and the 6.5 Ahr batteries were
down to 2.6 Ahr after 160,000 miles. Yet the hybrids were still
delivering high mileage equal to what they had been doing for the
duration of their service. If hybrid mileage were a function of battery
energy capacity, it should have decreased over time and it didn't.

The data suggests that round-trip effeciency of the battery system is
more important than anything else.

Bob Wilson

Posted by bob on April 24, 2008, 2:21 am

good post  - i often wondered, how bout a regular 1.5L engine prius, no
batts, but the same aerodynamics. i bet it'd be a 45mpg car with similar


Posted by e on April 24, 2008, 3:53 am
 bob wrote:

Worse mpg, and you'd be less satisfied with the low end

The traction battery and motor system fills a very small
but important gap. The battery capacity can diminish
considerably over time (and it will) yet do the job

An Otto-cycle engine (like that in the Echo) is
reasonably fuel-efficient at cruise, and has reasonable
low-end acceleration. The Prius' Miller-cycle engine
(not Atkinson, not Otto) is extraordinarily
fuel-efficient at cruise, but does a poor job of
accelerating from zero at acceptable combinations of
engine RPM and transmission ratios. An electric motor,
on the other hand, has maximum torque at zero RPM. It's
a nice marriage. That is the primary function of the
electrical side of the power train - to make the car's
initial acceleration acceptable. The "stealth" cruise
under 43mph, etc. is a relatively unimportant bonus.

This means that to convert a Prius-style hybrid into an
"electric car" requires a massive concept change:
expansion of the electric energy storage system, and
reconfiguration of the energy management and charging
system. It's a transition from the original hybrid
concept into an electric car with both plug-in charging
and on-board ICE charger.

Nevertheless, I'm considering adding 50 miles of battery
to my '04, since I can get lithium cells at no cost and
only drive 800 miles a month.

Posted by Chas Gill on April 24, 2008, 8:12 am

How very succinctly put!  Thanks for this - when others ask, I will refer
them to this text.


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