Ron, check out the new batteries from A123systems, who might be very supportive
of
your efforts. http://www.a123systems.com/html/home.html

Thanks for all your info.

Is it possible to just double up the existing batteries? Who can give me
installation
info on the over ride switch that is installed in the Prius for other markets?

allen



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From: priusplus@yahoogroups.com [mailto:priusplus@yahoogroups.com] On Behalf Of
Ron
Gremban
Sent: Wednesday, December 21, 2005 2:06 AM
Cc: murdoch@...; priusplus@yahoogroups.com
Subject: [priusplus] Re: Honda Supercaps Web Page/PHEV design exercise



Thanks for your pointer to this page. As there isn't anything private,
I am taking the liberty to post my response to the PriusPlus group.

I fully believe that supercaps will eventually replace batteries in
conventional hybrids. They have all the right characteristics and need
just a 2-3x improvement in specific energy and cost.

However, PHEVs that are designed to handle the full range of ordinary
driving conditions including up and down mountain passes, must be able
to deliver and accept near-acceleration-level power continuously, and
are therefore less likely to benefit significantly from supercaps. I
got inspired to go through a preliminary PHEV design process to see how
it might really come out:

Note: in all of the figuring below, I assume an electric
motor/controller/transmission efficiency of 75%, so that it conveniently
requires 1 kW from a battery to produce 1 hp (746W) of mechanical output
at the wheels. To convert an ICE's output to equivalent electrical
input then requires multiplying its kW rating by around 1.25 (assuming
6% drivetrain losses) or its hp rating by 0.94 -- rating the Prius' 76
hp/57 kW engine's equivalent electric input at 71 kW.

Let's imagine two Prius-class PHEVs (at 3300 lb GVW, to match the weight
at which the Prius' acceleration and hill climbing abiltity were
measured) -- one keeping the existing ICE, the other designed from the
ground up. To keep up with a Prius as well as with non-sports ICE cars,
it needs to have a top speed of around 100 mph (combined ICE & EV), be
able to cruise all day at 80 mph with a headwind (ICE only), accelerate
0-60 mph in 10 seconds (combined ICE & EV), and climb a 6% maximum
freeway grade mountain pass at 70 mph (combined ICE & EV for 20
minutes/7400 vertical ft).

Flat and level: My best guess is that an electrified Prius would
require around 25 kW from a battery to travel 80 mph (312 Wh/mi); 13 kW
for 60 mph (217 Wh/mi -- also a good figure for city driving); and 18 kW
for 70 mph (257 Wh/mi). A 20/40/60 mi EV range at 60 mph or city
driving would require 4.3/8.7/13 available kWh from a battery, or a
7.2/14.4/21.7 kWh battery discharged to 60% DOD (for long cycle life and
large remaining emergency energy supply). 60% normal depth of discharge
(DOD) yields a 40%, or 2.9/5.8/8.7 kWh, reserve.

If a headwind adds 40%, 35 kW would be required at 80 mph (25 kW at 70
mph). This means that the minimum ICE size for all-day driving is
35/0.94 = 37 hp or 28 kW. Let's size the ground-up PHEV's ICE at 28.5
kW, exactly half the Prius ICE's rating. These two engines' ratings
then translate into 71 kW and 35.5 kW equivalent electric input (these
figures are used below).

Hill climbing: I have driven my Prius, lightly loaded (say 3300 lb
GVW), up Donner Pass (6% maximum freeway grade) at 70 mph. This
requires 37 mechanical hp plus probably about 16 hp for
straight-and-level driving at 70 mph, or a total of 53 hp at the wheels
(1 hp = 550 ft-lb/sec). The engine is rated at 76 hp, but only 75% is
available at 7500 ft altitude. This leaves 57 hp, of which 4 hp is
probably lost in the drivetrain, leaving the required 53 hp and
validating my experience.

The 53 hp for the maximum 6% freeway climb at 70 mph (above) translates
into 53 kW from a battery. The Prius' engine can provide all of that;
the ground-up PHEV's half-sized engine could provide 26.5 kW, leaving
the other 26.5 kW to come from the battery -- a total of 8.8 kWh in 20
minutes. A 60-mile, 60% DOD PHEV battery has enough reserve energy when
"empty" to accomplish this, while a 40-mile one would have to have 1/3,
or 13 miles, of its range remaining to do so. A 20-mile battery has
only 16 minutes of this sort of uphill capacity even when full. In any
case, going down the grade will produce 37 - 18 = 19 kW that the battery
can hopefully keep accepting for 20 minutes (6.3 kWh total).

Acceleration: 0-60 mph in 10 seconds averages 8.8 ft/sec*sec, or
0.275g. At 3300 lb GVW, it should therefore require an average of 73 kW
plus maybe 9 kW average to offset normal driving friction increasing
from zero to 18 kW @ 60 mph, for a total of 82 kW (200 Wh total). The
Prius battery is rated at 21 kW (10 seconds => 58 Wh total), leaving 61
kW to come from the 71 peak kW ICE, which is reasonable. The ground-up
PHEV's half-sized engine would therefore provide 30.5 kW, leaving 51.5
kW to come from the battery during 10 seconds of acceleration (143 Wh
total).

Therefore, we have the following battery requirements:

Prius Prius Ground-up
HEV PHEV PHEV
0 kW 0 kW 0 kW 80 mph continuous driving (ICE only)
0 kW 18kW 18kW EV driving, 70 mph, to full EV range
21kW 21kW 51.5kW Acceleration, for 10 seconds
24kW same same 24kW Minimum deceleration regenerative
braking to capture most careful braking
>200kW same same To accept full maximum deceleration
0 kW 0 kW 26.5kW 6%, 70 mph climb @ 7500 ft altitude, for 20 minutes
0kWh 0kWh 8.8kWh 6%, 70 mph climb @ 7500 ft altitude, for 20 minutes
19kW same same 6%, 70 mph downgrade
6.3kWh same same 6%, 70 mph downgrade

Note that the Prius-engined PHEV's acceleration requirement is barely
larger than its maximum steady-state requirement (21 kW vs. 18 kW), but
that the acceleration requirement for the ground-up PHEV is 185% larger
than that and double its hill-climbing requirement. The latter could
benefit from a bank of supercapacitors for acceleration, but not the
former. Both have a 19 kW downgrade regenerative braking requirement
that is around the same size as the maximum seady-state drain.

murdoch wrote:

>bcc: various
>
>I have lost track of the number of times I have seen "ultra" or "super" caps
>ruled out of a hybrid project for this or that reason. This page by Honda is a
>bit of a reminder that some companies are persisting in not ruling out
>advanced-capacitor tech. Note the chart in the bottom right-hand corner
>indicating a comparison to their NiMH they use in their conventional hybrids.
I
>do not at all mean to downplay the weak points of capacitors or imply they are
>the solution in all hybrid challenges... only to make sure we keep them in mind
>as we debate all manner of new vehicle propulsion solutions.
>
>http://world.honda.com/FuelCell/FCX/ultracapacitor/charging/
>
>
>

--
+++++++++++++++++++++++++++++++++++++++++
Ron Gremban, rgremban@...
California Cars Initiative, a nonprofit organization:
http://www.CalCars.org
Moderator & Technical Lead
http://www.priusplus.org
PRIUS+ PHEV Conversion Group: http://groups.yahoo.com/group/priusplus
Newsletter: http://groups.yahoo.com/group/calcars-news
Do-it-yourself PHEVs: http://www.seattleeva.org/wiki/EAA-PHEV
+++++++++++++++++++++++++++++++++++++++++




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