Re: my very heavy and lossy EV LandCruiser idea... :-)

[Lee Hart <leeahart@earthlink.net>]

Byars, William wrote:
> the 'Cruiser would weigh around 4,700lbs with 36" tires on it, standard
> 4-speed tranny and a soft-top or no-top. Roughly 1,700 lbs of batteries
> (24 Optima YT's) so about 36% battery weight. I entered in that the
> truck would weigh about 3,000 prior to conversion, and I'd take out
> 1,000lbs...
> Really, it does take almost 100hp to push it down the road at 65-70mph!
> This truck would lose an aerodynamics contest to a 4' x 8' piece of
> plywood held sideways!

Well, I poked some numbers into my EV spreadsheet; here's what it said:

Land Cruiser HP vs. Speed Calculations, by Lee Hart on 11/29/99

HP = rolling resistance + power train loss + aerodynamic drag
  rolling resistance = R W V / 375 where  R=tire roll resistance    0.01
                                          W=vehicle weight, lbs     4380
                                          V=velocity, mph             10
  power train loss = C W V^2 / 375        C=loss coefficient      0.0002
    (I^2R, gear, bearing, stirring etc.)
  aerodynamic drag = Cd A V^3 / 146,625   Cd=drag coefficient        0.5
                                          A=frontal area, sq.ft.      32

motor: 2 Advanced DC L91, 30 HP at 192 volts, 135 amps = 86% efficiency

batteries: 24 Optima    12 v each       weight each (lbs)             45
        25% of curb wt  288 v total     amp-hrs (20-hr rate)          65
        175 minutes at  25 amps         Peukert amp-hrs              104
        1199 minutes at 4.42 amps       Peukert exponent            1.11

mph             10     20     30     40     50     60     70     80
motor HP out    1.51   4.14   8.55   15.39  25.32  38.99  57.05  80.16
efficiency      29%    52%    69%    79%    85%    88%    89%    88%
watts input     3923   5899   9235   14474  22214  33139  48052  67924
amps            14     22     34     53     81     121    175    248
minutes         326    207    126    76     48     30     20     14
range, miles    54     69     63     51     40     30     24     18

I used the aerodynamics of a 4x8 sheet of plywood sideways. I assumed
3000 lbs stripped, plus 300 lbs for motor and adapter, and 24 Optima
D750 batteries. That gives a 288v pack, so for expediency I assumed two
Advanced DC 6.7" L91 motors. They have about the right HP and voltage
when used in series.

Notice it only took 34 HP at 60 mph, but 80 HP at 80 mph (you can really
see the consequences of poor aerodynamics). 24 Optimas is ony 25%
batteries, so range is poor. But weight is 4380 so there may still be
room for more. Also, range is pretty good at very low speeds, as when
creeping around off-road.

These are just range and power figures at constant speed, on smooth
pavement, on level ground, with no headwind, and running the batteries
to 1.75v/cell (100% discharged at the given current). As a practical
matter, I use 1/2 of the range prediction as the real-world range.

But as Bill Dube' points out, this is all just calculation. The best
approach is to get the actual numbers from real Land Cruiser EV
conversions, and base your predictions on them.
-- 
Lee A. Hart                     Ring the bells that you can ring
4209 France Ave. N.             Forget the perfect offering
Robbinsdale, MN 55422 USA       There is a crack in everything
(612) 533-3226                  That's how the light gets in!
<leeahart@earthlink.net>                Leonard Cohen