This is copied from the NEDRA Yahoo group.
Posted by: "John Wayland" jw@plasmaboyracing.com evdragracer
Sun Aug 29, 2010 9:04 pm (PDT)
Hello to All,
Perusing my junk mail file, I came cross a couple of emails that
were for some reason, diverted into it and I never saw them until
now.
Though many of the answers to the questions raised here are at my
web site's 'White Zombie History' in the 2010 section, I'll take
some of them on. In addition, I've included what I've been up to
in my back yard EV laboratory recently.
On Aug. 8th lithiumstart wrote:
Hi Mike,
You are proposing one zilla per motor. Can you say why you think
WZ will go faster with that change? I think the motors will
produce exactly the same amount of power with one Zilla per motor
as they are now with one Zilla running two motors in series, but
WZ would then have to haul around another Zilla, which would make
WZ slower due to the weight!
With the powerful LiPol pack now in the car and the promise of a
heady 2,400 amps available, I have planned all along to
eventually run twin Zillas, with the idea to do it only when we
had wrung-out all the speed and power we could get from the
single Zilla configuration...considering we were up against the
rev limiter for the final 2 seconds of our twin 10.4 runs, it's
obvious we're not to that point yet
At this time with
things, I agree with Thomas. Instead of adding the extra 30 lbs.
and complexity of a second Z2K - even though I have a spare Z2K
on the shelf and there's enough battery power to feed twin Z2Ks,
I am instead pulling out the pair of parallel contactors, various
relay controls and brackets, and the extra heavy cables that make
up the series/parallel setup, shaving off ~ 20 lbs. of weight.
This will lighten the car, simplify the wiring, and really clean
up the under-hood area as well. We believe there's more
performance to be extracted just the way the car is by finding
the perfect gear ratio, so for now that other Z2K will remain on
the shelf.
On another point, it's weird having been one of the first to use
series-parallel motor shifting - used to do it manually with the
tweaked 1400 amp Gozilla controller, and considering that I had
been involved with Otmar in the earliest concept-design stages of
the Zilla line of controllers and that I have ben a big proponent
of the effect, to now be hard wiring the car in series mode, but
the batteries are so stiff there's just no need to do the
parallel shift anymore.
As the batteries are capable of more power than they are being
used for now, WZ might be able to go faster by taking out
batteries until it has just enough on board to still produce
170V@4000A=680kw while using one zilla per motor. The 170v and
4000a is obviously on the motor side, on the battery side it
might look more like 284V and 2400A. WZ would then be faster if
more weight can be removed from the battery pack than the Zilla
added.
As to taking out batteries, that's a definite 'no'. Thomas could
be correct in that doing so the lighter car would be even quicker
- the Dow Kokams certainly have the suds to crank out higher amps
as would be required with a smaller pack at lower voltage, but
pulling batteries means dropping the car's range capabilities.
There's still more performance to be had with the current full
sized pack configuration, so a smaller lower voltage pack isn't
part of the plan. The Zombie's mission has always been to dispel
EV myth that EVs are slow, dull, and boring, and through
demonstrated performance show that they are exactly the opposite
and are in fact, fast, fun, and exciting. With the change to
these powerful Dow Kokam cells we've now added 100+ mile range to
the mix, so we're underscoring the 'street legal' part of the
Zombie's capabilities. In addition to the most obvious feature of
being running low 10s in a street legal car driven to and from
the track (no trailer needed), we also remove the 'have to charge
between runs' stigma as we drive past our pit area and return to
the staging lanes to run again and again. Perhaps the best
exclamation mark we could put on things though, is having a 10
second electric car that can also run 100+ miles per charge on
the open highway! Removing batteries would negate these
attributes. We feel that we can run deeper into the low 10s and
possibly even into the high 9s without resorting to pulling
batteries and reducing the pack's 22.7 kWh storage capacity. If
the Zombie was in the modified conversion class and the only goal
was to go as quickly as possible in the 1/4 mile, in addition to
a downsized battery pack there would be Lexan windows, a gutted
and stripped interior, and other weight reducing efforts... I
have no desire to do this. Instead, the car's fit, finish and
overall look will continue to be refined as it becomes an even
better street car. We are very close to having a body and paint
sponsor, and with that type of make-over comes a new headliner,
new carpets, and new interior materials that will bring the
Zombie closer to the Meanie's look and feel...Don't worry, the
sponsor's stickers will go back on
On the pair of 10.4 runs, data extracted from the Bruce
Sherry-Manzanita Micro BMS indicated the Dow Kokam cells had a
peak output of 539 kW of power for 722 hp of electrical energy
from the pack, so there's still quite a bit more battery power to
tap into, if we decide to access it. As mentioned, we were on the
rev limiter the last 2 seconds of those 10.4 second runs. Tim
felt it flatten out cease accelerating, the data graph posted at
my web site confirms this, and so does a mph calculator that's +
or - accurate to within 1% that shows that with the 3:70 gear and
the 6600 rpm limit we chose, the top speed of the Zombie was held
to 122 mph - we did 121 and some change! That same calculator
shows that with a 3:50 ratio and the same rpm limit the car has
the capability to hit 129 mph (if there's enough hp to get the
job done). We are now doing this gear ratio change - going
'taller' again (but numerically lower) from the 3:70 ratio to the
new 3:50 gear set. We're confident we won't need to turn up the
juice to go quicker. The trap speed should increase to somewhere
between 126 mph and the rev-limited 129 mph that the 3:50 gears
provide. The big question is, how will yet another change to
taller gears affect the hole shot? In gas cars, it's predictable
that when you go taller in gears, the hole shot gets worse but
the top end gets better. EVs have all that luscious bottom end
torque though, so the same effect does not necessarily apply. In
the Zombie, as we've gone taller in gear ratio the hole shot has
improved along with the top end. Going from the 4:11 gear set to
the 3:70 set the 60 ft. went from 1.70 - 1.72, to 1.61 - 1.64,
then when we got the bugs worked out, it dropped to 1.58 and we
got that scream'n 6.487 @ 107 mph 1/8 mile! Now we're going to
the 3:50 ratio, but where does the bell curve start going over
the top and down the other side? It's possible the hole shot and
the 1/8 mile might suffer by going taller with the gears, but my
gut tells me it won't...guess we'll have to wait until sept. 10th
to find out! If the hole shots doesn't get better while also not
getting worse, the ET should still drop to very low 10s solely
because the car will continue to pull those last 2 seconds at the
far end of the track and break through the 125 mph barrier for
street cars. If the hole shot worsens but the top end is better,
the runs might stay in the mid 10s. However, if the hole shot
actually improves while the top end is also better - lookout,
here comes the 9s!
In contrast to the idea of less stuff (pulling modules) and going
more for the all-out racing results, I am currently upgrading the
car's interior to where I wanted it to be before we ran out of
time to make the WIV races. Little annoying things like the
interior kick panel carpet pieces that were not yet glued back in
(the stock 1200 pieces were cardboard-like covers), the rear seat
area's vinyl and carpet pieces that again, were not yet back in
place, door panel bright metal trim pieces we couldn't find while
the shop was in disarray, etc., are now being taken care of.
Something that is quite frustrating for me, is reading various
Internet stories about our recent strong runs that say the car is
'stripped down' or 'gutted', when that is completely incorrect.
On the outside, every bit of the car's stock items are intact
including the original bumpers, grill work, etc. On the inside,
carpet in both the driver's side and passenger side is something
the car didn't even come with from the factory - 1200s were very
cheap little cars with a lone thin carpet piece draped over the
tranny tunnel, but then only thin vinyl floor mates front and
rear. The stock dash is still there, as are the door panel covers
and the rear quarter panel covers.
Other much needed changes are being made, such as a rewire of the
entire under-dash 12V harnesses, connectors, and wire bundles.
The new 'EVision 2' system is now installed, so we are no longer
driving blind and once again have all the capabilities of Victor
Tichonov's wonderful product! The beefy 2000 amp high tech
shunt/circuit board was custom set up for the Zombie, and it's
great eye candy as viewed from behind with the trunk open. As
always, I mounted this unit not only for best access, shortest
cable routing, and with power-voltage safety in mind, but to also
have it visible to all...gotta show the world the great
innovations and designs of the hard-working electronic guys who
support our racing endeavors! You can see the shunt board's
status green power and amber communications LEDs aglow that are
now part of the light show that pulls in the press like a magnet
in the darkened pit area when we race at night. When all 12 of
the Sherry/Rudman 8 ch. reg. boards' green bypass LEDs are
pulsing (96 of them), the same boards' blue communications LEDs
are flickering, the 4 ch. reg, board that protects and monitors
the 13.4V lithium 12V system has its red bypass LEDs flashing,
and now the LEDs of the shunt board are lit, it's as if one has
that little access panel on the head of the android 'Data'
hinged open to expose the syntax flashes of light from his
positronic brain (Star Trek the Next Generation). Under the hood
is more interesting as well, where the EVision 2's CPU is now
mounted to the firewall with its tiny amber LED flickering, the
LED of the hairball lit, and the water pump's inverter LED also
on.
On the inside of the car, I'm working on a new dash piece that
replaces the former radio space plate that had housed the Emeter,
status lights and 15V analog gauge. It will now have the
EVision's rotary 20-function selector and the Wayland-inspired
'Favorites' buttons...three push buttons that toggle the display
to 'Race', 'Street 1', & 'Street 2'. The EVision's LED gauge
display was custom colored for me by Victor and now is more
securely mounted to the steering column with a trick factory-like
mount. Victor and I have hooked up more of the feature sets than
I had previous used. For example, when the car's original gas
filler door (now the charge port door) is opened, the EVision
kicks into 'Charging' mode where the beautiful display wakes up
and a flashing red 'charge' indicator reports that status while
the 'Amps' display changes from amps being drawn from the pack,
to amps being pumped into the pack. The shunt board in the trunk
has a second smaller shunt just for charge monitoring duties.
When the pack comes up to full charge, the word 'Done' lights up
green to the right of 'Charge'.
I'm still hoping John well tell us how much the whole battery
assembly weighs as it sits in the car now.
There are 192, 1.8 lb. cells, so that's 346 lbs. in actual cell
weight. There are 16 cells in each module. There are 12 modules,
11 of them with their BMS, fan cooling and protective covers
weigh 39 lbs. 14 oz. each, while the 12th module that has extra
aluminum mount brackets integral to the module weighs a bit
more...call it 40 lbs. per module. That's 480 lbs. Quite frankly,
the use of 1/2 inch Lexan and very thick copper interconnects
makes each module about 6 lbs. heavier than they need to be and
with lighter duty pieces they would have weighed more like 34
lbs. each for a total pack weight of 408 lbs., but then again we
don't worry about over-heating interconnects or battery case
weakness
There's also about 5 lbs. of buss bars and 1/0 cable
inter-connects that electrically tie the modules together in
series, so the entire pack weighs 485 lbs. There is also the
Lexan full pack protective cover, the aluminum pack surround
restraint, the base plate the pack sits on, and the wide blade
and clamp system that secures the pack to the car - because Marko
and I really thought these parts out and utilized a
strong-but-light policy, this only amounts to about 15 lbs. The
entire installed 355V pack rated at 22.7 kWh @ C2 and 2400 amps
max discharge @ <10 seconds, with all its peripherals weighs
right near 500 lbs. For a comparison point, the outgoing 360V
lead acid pack with ~6 kWh @ C2 and 1500 amp max discharge with
all its peripherals weighed right near 900 lbs.
Comparison:
Lead acid pack - 900 lbs., 360V @ 6 kWh (sags to < 200V at full
1500 amp load), 11.8 ETs, 0-60 in 3.5 seconds, 30-35 miles range
LiPol pack - 485 lbs., 355V @ 22.7 kWh (sags to >300V at 1800
amps 3/4 load), 10.4 ETs, 0-60 in <2 seconds, 100-120 miles range
About the motors: I can't imagine that there would be much
cooling possible with air during a 10 second race, or less! I'll
bet heat usually isn't the problem if you start cold
We pump compressed air through the Siamese 9 motor sections while
the car is in the pit to both cool the armatures and coms/brushes
and to blow-away brush dust that when accumulated can make a
conductive cloud inside the motors to help light off a fireball
under very high voltage loads. I am working on a continuous
fan-forced cooling system for hours-long street driving where my
real concerns about heat are.
Still on the schedule is finishing the 12V rewire, finishing
interior improvements, chasing down and fixing the driveline
vibration, and getting the car to a local scale to weigh it to
see how close my estimate of 2275 lbs. was...I say 'was', because
that was with the Siamese 8 motor. I'm told the Siamese 9
(Impulse style, so they're shorter than regular 9s) only weighs
about 25 lbs. more than the Siamese 8, so the weight estimate is
right near 2300 lbs.
Hope I've answered the questions I had missed earlier in the
month.
See Ya...John Wayland
