--- Ron Gremban <rgremban@...> wrote:

> 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
> steady-state drain.
>

Hi Ron;

I LIKE that, or "Prius done right!" The figures
look good. Hafta try that setup in one of our Sunrise
bodies when/if we get this one going.They are lighter
than the steel bodied Prius, two of us could pick up
the basic Sunrise shell! It would be a great test bed,
for a ground up Prius Done Right. Hope we, Jerry Dycus
and a few other EV Listers can get this up an'
running. Check out EV Production Group on Yahoo.I'm
puttinhg the cart before the horse, sorry, but your'
rithmetic, to me, holds up! Hell! YOU're the Engineer
here<g>!

Seeya

Bob
> 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/
> >
> >
> >
>
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