# [EVDL] article: “It’s A Brick” – Tesla Motors’ Devastating Design Problem



## EVDL List (Jul 27, 2007)

Tesla design problem leads to horror stories:

http://theunderstatement.com/post/18030062041/its-a-brick-tesla-motors-devastating-design

Anyone know why these batteries are dead once fully depleted?

-- 
*Paul Wujek* <[email protected]>
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## EVDL List (Jul 27, 2007)

If they are building the packs with laptop batteries, I think a number
of us have had the experience of letting our laptop or cell phone
fully discharge turning the device into a "brick". Sometimes you can
recover a little bit, maybe half the original power. This happens in
Pb batteries too. The old wives tale of leaving your car battery on
concrete will kill the battery... well once it makes it to concrete,
people don't tend to them and forget them. Over time the plates
sulfate up and it's very hard to get good service from them after
that. I imagine LiPO4 chemistry is different... but an anode may be
depleted to cruft up a cathode somewhere.

If the car would shut off entirely at 50% power during long periods of
being unused, wouldn't that prevent them from becoming bricks so fast?
Seems the on board system could give customers warnings about storage
below a certain threshold.

sean



> Paul Wujek <[email protected]> wrote:
> > Tesla design problem leads to horror stories:
> >
> > http://theunderstatement.com/post/18030062041/its-a-brick-tesla-motors-de=
> ...


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## EVDL List (Jul 27, 2007)

What I don't understand is why they don't have all systems shut down
once the battery reaches what is considered empty. There could be an
override switch which works for just a couple of minutes to get the
vehicle out of gear for towing and then it could go back to
hibernation until it gets power from the wall. Maybe this is an
example of why using LiFePO4 cells might be better. They don't require
so much thermal management and extra stuff. I realize that the energy
density isn't as high but they do have a longer cycle life.



> Paul Wujek <[email protected]> wrote:
> > Tesla design problem leads to horror stories:
> >
> > http://theunderstatement.com/post/18030062041/its-a-brick-tesla-motors-devastating-design
> ...


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## EVDL List (Jul 27, 2007)

> Tesla design problem leads to horror stories:
> http://theunderstatement.com/post/18030062041/its-a-brick-tesla-motors-devastating-design

I would suggest caution in taking this article at face value. It may be 
fact; but it may also be fiction. It bothers me that there are no names, 
dates, or other verifiable information presented.

-- 
If you would not be forgotten
When your body's dead and rotten
Then write of great deeds worth the reading
Or do these great deeds, worth repeating.
-- Ben Franklin, from Poor Richard's Almanac
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

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## EVDL List (Jul 27, 2007)

Lee,
I totally agree with your assessment. However, ..... I would venture on
the "limited" study that I have done that balancing lots of little cells
(as Tesla has chosen to do) would prove to be problematic. Unless the
packaging of the cells was multiple small cells in parallel to make a
decent size "modular block" that they could monitor individually, that
Tesla might run into a situation where their BMS might not be able to deal
with the irregularity of charge states they are seeing in the cells in
their packs. Anyone that has ever done a conversion knows that one battery
(or even a cell) in a larger series string, can cause an apparent total
loss of capacity. I do not know anything about their BMS, but maybe a
little look into their technology might be the telling tale. Does anyone
know anything about what Tesla publishes about their BMS?

I can kill a cell real quickly, and I can make one last a long time if I
control its charge/discharge cycle. The problem for engineer's here is
controlling their charge/discharge cycle, on every cell in a series string.

Mike





> Lee Hart <[email protected]> wrote:
> 
> > > Tesla design problem leads to horror stories:
> > >
> ...


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## EVDL List (Jul 27, 2007)

I also agree with you Lee. This "Brick" report inckudes no valid
documentation.

Also I would suggest (Although this is pure conjecture on my part.) that
the dificulty may simply be the discharge voltage has gotten so low that a
properly drsigned "Automatic" charger refuses to charge an extremely low
voltage pack. In the past we have had to use a "Dumb" charger to bring up
the charge to a minimum level before the "Automatic" charger would start to
charge. I have gone so far, for example, with NiCad cell packs as to
"Shock" individual cells with 12VDC to "Zap" any shorting dendrites and
when the voltage after one or two seconds of "Hyper fast charging" and the
individual cell voltage has come up to at least one volt (Out of normal
about 1.25) then charge at normal rate while monitoring temperature (I did
not seek an explosion from high temperature indicating cell was damaged )
and often the NiCad cell was recoverable from zero in this manner. As I
said I only tried this on a lap-top pack once, but it did work that time.
once is not a validated history! So I leave it to the expertice of EVDL
members to consider if a process such as this might be safe and effective
enough with the 6000+ individual cells in the Tesla pack.

Another important point for EV public relations would be to note that only
Tesla is using this unique battery chemistry and pack construction
methodology. And no other EV has this exact problem! Nor do we fail to have
a proper disconnect for longer term parking without "Parasytic Discharge"
in our designes.
Regards,
*Dennis Lee Miles*

++++++++++++++++++++++++++++++++++++++++


> Lee Hart <[email protected]> wrote:
> 
> > > Tesla design problem leads to horror stories:
> > >
> ...


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## EVDL List (Jul 27, 2007)

> Mike Willmon wrote:
> > Lee,
> > I totally agree with your assessment. However... I would venture on
> > the "limited" study that I have done that balancing lots of little cells
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> 
> > On 2/23/2012 5:00 AM, EVDL Administrator wrote:
> > > For the Prius, I doubt that Toyota would have used cells much larger,
> ...


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## EVDL List (Jul 27, 2007)

> On 12-02-23 10:06 AM, Lee Hart wrote:
> >> > If Ovonics/Cobasys hadn't been so restrictive in their NiMH licensing, I
> >> > wonder whether Toyota might today be looking at NiMH for their new RAV4-EV.
> >> > After all, NiMH proved itself very well in the earlier model. In some ways
> ...


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## EVDL List (Jul 27, 2007)

>> The license agreement limited them to 7ah or less; the Prius cells are
>> therefore 6.5ah. I think they looked at how much energy they needed,
>> divided by 6.5ah, and came up with the 228-cell pack. If they had been
>> allowed 13ah cells, it would have been a 114-cell pack.



> Zeke Yewdall wrote:
> > I am not so sure of this... wasn't the desired voltage part of the design
> > as well? A 114 cell pack would only about 140 volts, vs around 300 that
> > they used. More, smaller, cells would be required to get to that voltage,
> ...


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## EVDL List (Jul 27, 2007)

>> The license agreement limited them to 7ah or less ...



> EVDL Administrator wrote:
> > I recall hearing this before. I've also heard that the limit was "less than
> > 10ah."
> 
> ...


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