Wet Cell-Powered tZero?...Yeah, Right!

[John Wayland <dat1200@EUROPA.COM>]

Hello to All,
      In response to Lee's theoretical T-125-powered tZero, all I can
say is, "Lee...you ignorant slut!" ;-) It's been a long time since Lee
Hart and I had something we could argue about and really sink our teeth
into. Lee and I are good friends, and we love to dice it out once in a
while, so I'm going to take this opportunity and roast his chestnuts
over the fire!  Lee's comparison of the tzero with 28 Optimas vs the
tZero with 20 T-125's, while looking almost believable on paper, is way
off from reality......allow me to explain.
     Lee's concept of a tZero with 20 T-125's isn't even possible, as
the large, maintenance-intensive batteries simply couldn't fit into this
small, stylish sports car's body. The entire concept of the tZero, was
based on using AGM type batteries that could be placed in restrictive
areas. The AC Propulsion crew took advantage of the small physical
dimensions of each Optima module, and knowing that they could be placed
sideways or upside down, they stuffed 28 Optimas into that tiny
fiberglass car in ways that no big, awkward, oozing wet cell could ever
be used....heck, the thing even has batteries in the doors (lets see you
do that with big, chunky wet cell 6 volters)! There are batteries placed
all over the car, in tight, out of reach confined areas, but the overall
weight balance of the car is superb, again due to the fact that the
batteries are small, can be oriented in any position, never need
maintenance, and are easy to fit into the spaces available.
     I could stop the argument right here and now, as given the above
reality check, the rest of Lee's points are mute, but out of interest,
and to further educate folks like Mike Brown who have expressed their
curiosity over the popularity of Optima batteries, let's continue to
debunk the rest of the fallacies about wet cells being comparable to
Optimas.
     In his example of what it would take to deliver good acceleration
performance in the tZero by using a set of twenty T-125's, Lee explained
that the T-125 could crank out 1000 amps while sagging to 5 volts under
that load. He also explained that the set of 20 T-125's would indeed,
have to be able to deliver that kind of current, in order to provide 100
kw of power. He went on to estimate that this would give 0-60 mph in
seven seconds. After this, he went on to tout the cycle life of the
T-125 as being around 700 cycles, saying that the T-125's gave a 4:1
advantage in cost of ownership, over a set of Optimas.
     Problem number one...the cycle life on the T-125 is actually 650
cycles, not 700. I realize that Lee was only estimating the cycle life,
but when you're talking battery cycle life,  50 cycles is a huge
difference.
   Problem number two....a 1000 amp discharge out of the T-125's for
each 0-60 acceleration run, amounts to abuse of the battery pack! In
their normal distributed literature, Trojan doesn't even list a cca
rating for their deep cycle 6 volt batteries, because the specific
design application for these batteries (golf cars) doesn't ever require
such currents. I talked with Trojan's Steve Carter, and my guess on the
cca rating for a model T-125 was right on target at 600 amps. A 1000 amp
discharge is almost twice that rating! I also asked Steve what the cycle
life of the T-125 would fall to, if it was subjected to 1000 amp
discharges, and gave him the 0-60 scenario and the likelihood that it
would be used often by the driver of a tZero. I asked him if it would be
about half. His response? Steve said we'd be lucky to see 200 cycles
under those kinds of frequent discharges!
    Optima, on the other hand, is proud to list their cca rating of
their little deep cycle YellowTop battery, so much so that it is an
integral component of the official 'D750S' part number, and a 750
discharge doesn't stress-out these tough little batteries. Moreover, in
the tZero, the highest discharge that is actually seen by the battery
pack is less than 500 amps. So in this case, we have a battery that can
easily put out 750 amps but that is actually loafing along at less than
500 amps in this application. Recapping this now....the T-125 is being
tortured at almost double its design rating, and the Optima is being
pampered with 2/3 of its rating....what was that about cycle life?
       Lee admitted that the 0-60 run in seven seconds wasn't as quick
as the tZero's 0-60 of 4.9 seconds, but said that it was still quick and
even better than the GM EV1's 0-60 of approximately nine seconds. I
would agree that 0-60 in seven seconds is impressive performance, but in
the world of 0-60 times, 4.9 vs 7 is like comparing the takeoff in a
bug-squasher Cessna 150, to being strapped in an F-16 fighter jet! So
his comparison is off balance and not an apples to apples situation. You
cannot take two vehicles....one that blasts to 60 mph in under 5
seconds, and the other that takes 7 seconds to hit 60 mph, and say that
they have approximately the same kind of acceleration, because there is
a mountain of difference in those two times!
      Lee next stated:

>Flooded cells *can* give you performance, range, and cycle life >at the same ti
 me. They cost a lot less, too.

        Where as a general statement this true, when used in the context
of the above comparison (28 Optimas vs 20 Trojan T-125's), as Lee is
doing, it simply isn't so. The set of 20 big 6 volt wet cells did not
give the same kind of performance...not even close! And under the kind
of blast-off accelerations, hill pulls, and high speed driving that the
tZero has already been subjected to, the T-125's would already have
warped plates and a decline in both performance and range, due to the
dramatically reduced cycle life (direct quote from Trojan).
        Perhaps if the car in question wasn't the tZero, but instead,
was big and boxy, Lee really could get all 20 of those T-125's into
it...but then what would be the point? The whole benefit of Optimas, or
for that matter other AGM style batteries, is that they open the doors
to high voltage power, creativity and freedom. You can have awesome
acceleration, range, and proper space utilization with Optimas....you
can't with wet cells...that's the truth, like it or not!
     Yes, wet cells still are an important option...they certainly
worked out great in the Red Beastie, and they were definitely less
expensive than a comparable set of YellowTops. They are also easy to
charge, and in more sedate EVs their cycle life is impressive. There
will be times where the wet cell battery fits a need and will be the
right choice, and there will be times where the Optimas are the way to
go.
       For me, I prefer to move forward with the EVs that I drive and
build. I have never liked the mess and gassing of wet cells...the
Optimas totally eliminate that for me. I have always wanted deep cycle
batteries that could also dish out high currents without the worry of
warped plates...the Optimas totally eliminate that for me, too. I have
always wanted to build EVs that weren't compromised by the restrictions
imposed when using wet cells...with Optimas I can place the batteries
virtually anywhere. In the past, using wet cells meant that my EV would
have a totally different range when driven sedately and on flat roads,
than when it was driven at higher speeds and on hills. With Optimas,
while there is still a difference between these two types of driving
conditions, it isn't nearly so pronounced.
      Is the Optima the perfect battery? Of course not, but with it's
small size, vibration-proof spiral wound construction, good cycle life,
high power density, low internal resistance, and  true maintainance-free
design, it is a dramatic step forward...one that I have waited many
years for!

See Ya..........John Wayland

Wet Cell-Powered tZero?...Yeah, Right!