# Is there ever a time...



## Ziggythewiz (May 16, 2010)

Didn't plasmaboy get his name doing something like that?


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## EVfun (Mar 14, 2010)

No, he got his name by dropping a wrench while making the last connection on a 336 volt pack of 16 amp hour Hawker Genesis batteries. The wrench (and possibly John's sanity) has never been found...


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## steven4601 (Nov 11, 2010)

Here is the race story / history of the White Monster.. It is quite amusing to read! I never knew he (Mr Wayland) had spend such a great amount of effort/life into making the 10second Zombie.

http://www.plasmaboyracing.com/reviews.php


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## Ziggythewiz (May 16, 2010)

Yeah, I was just joking, but I think the zombie did have a physical emergency disconnect that was essentially a busbar that pulled out of the circuit, and used some kind of shield to pretect the puller from the resulting plasma ball.

I think a plasma event would be likely every time you disconnect the pack, as it will be pulling max current and there's no way to turn down the current before disconnecting. It would be similar to driving at full throttle and turning your main contactor off. How many times can you do that safely?

Maybe it would be possible to do this somewhat safely in a drag car with supercaps where you only have enough power for 1/4 and don't need to turn it off because it's gone.


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## John Metric (Feb 26, 2009)

PhantomPholly said:


> Is there ever a time in racing when it would make sense to bypass the controller and (using separate contactors, or a two-way contactor that sends power either through the controller or directly to the motor) simply hook the motor directly to the pack? Or are the controllers so efficient that the difference is negligible? It seems as though that might be useful when milliseconds make the difference.


I would say a definitive NO. I can plot the power going into the Zilla and out of the Zilla and they plot nearly on top of the same line. I would say well within 1% after you get out of current control when you might think it might pay off. The loss of the emergency cutoff and over rpm protection and other safe guards inherent in the controller would negate any minute controller loss, not to mention the time delay in cutting off the power prior to opening the contactor and reclosing another one. (cause you don't want to make or break under power.)

John Metric
DC Plasma Racing on Youtube (please subscribe)
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DIYElectricCar
Pennocks Fiero Forum


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## Ziggythewiz (May 16, 2010)

John Metric said:


> cutting off the power prior to opening the contactor and reclosing another one. (cause you don't want to make or break under power.)


How exactly would one cut the power prior to opening the contactor?


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## Coulomb (Apr 22, 2009)

Ziggythewiz said:


> How exactly would one cut the power prior to opening the contactor?


I guess you'd leave the controller full on, so that connecting and especially disconnecting the breaker just subtracts or adds the few volts drop across the IGBT(s) or MOSFETs. Then 100 ms later, you turn off the throttle, and let the silicon stop the current, which is no longer conducting through ionised (low resistance) air.

I don't think I'd be doing it any time soon. But then, I haven't had the racing bug bite me yet.


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## PhantomPholly (Aug 20, 2008)

John Metric said:


> I would say a definitive NO. I can plot the power going into the Zilla and out of the Zilla and they plot nearly on top of the same line. I would say well within 1% after you get out of current control when you might think it might pay off. The loss of the emergency cutoff and over rpm protection and other safe guards inherent in the controller would negate any minute controller loss, not to mention the time delay in cutting off the power prior to opening the contactor and reclosing another one. (cause you don't want to make or break under power.)
> 
> John Metric
> DC Plasma Racing on Youtube (please subscribe)
> ...


Thanks - yes, that makes sense. If the loss is only in the realm of 1%, then the time spent switching from the controller to the "direct connection" might, like "shifting gears," lose you more time than you gain.


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## John Wayland (May 26, 2008)

Hello to All,

Haven't posted here for some time and thought it might be fun to add my two cents worth.

Metric is talking from the perspective of a drag car having a state of the art controller system that can feed all of a compact and very powerful lithium pack's might to a pair of motors... but the question presented was 'is there ever a time'...so in the interest of keeping EV drag racing history accurate, my answer is definitely 'yes'. All one has to do, is go here for all the details that include photos and time slips:

<http://www.plasmaboyracing.com/history/2004e.php>


Before others ever had the concept of building and drag racing an EV, in early 2004 I was successfully using contactor-direct bypass of the controller - successful enough to be the very first to build and push a street legal electric car to break 100 mph in the 1/4 mile. This was subsequently followed by the Zombie becoming the very first NEDRA street legal class car to run in the 12s... all of it only made possible 'because' of contactor bypass. 

At the time, Otmar and I had were collaborating together in the design of the Zilla series and the Z2K controller, but it would not be released until the following year. The most powerful controller then, was the Godzilla (so named by me) - mine was serial # 003 rated at 1200 amps. Eager to help get the Zombie off the line quicker, Otmar tweaked mine to crank out 1400 amps (the Godzilla model got as powerful as 1800 amps before the Z2K replaced it). The launch at 1400 amps was much stronger, but I still wanted more in my bid to be the first to push a street legal electric car over 100 mph in the 1/4 mile. This was long before stout lithium was available, and we ran on oh-so-heavy Exide Orbital lead acid 12V batteries. The pack was at just 240V, but had the capability to make 2000+ amps if the batteries were sagged low enough. The controller couldn't jam that type of juice, so at the point of the series-parallel shift, I decided to try connecting the twin 8 inch motors directly to the battery pack with a pair of Bubba contactors. It worked, breaking both rear tires loose at ~ 75 mph, pitching the car sideways a bit, and sending it on its way to just over 100 mph at 13 seconds almost on the nose. Later in the same month the ET dropped to the high 12s.

Yes, it was risky and prompted my use of the 'oh sh---' handle to disconnect the pack under full load - really lit up the inside of the car at night when it had to be used a couple of times 

In today's world with much more powerful controllers and LiPo cells that deliver all the power the controller can use, I agree with Metric that there's no need for such antics anymore... but the question was 'is there ever a time' - history shows there was 

See Ya...John Wayland

<www.plasmaboyracing.com>



John Metric said:


> I would say a definitive NO. I can plot the power going into the Zilla and out of the Zilla and they plot nearly on top of the same line. I would say well within 1% after you get out of current control when you might think it might pay off. The loss of the emergency cutoff and over rpm protection and other safe guards inherent in the controller would negate any minute controller loss, not to mention the time delay in cutting off the power prior to opening the contactor and reclosing another one. (cause you don't want to make or break under power.)
> 
> John Metric
> DC Plasma Racing on Youtube (please subscribe)
> ...


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## EV-propulsion.com (Jun 1, 2009)

Not that this is related to racing really, but years ago when the GE EV-1 controller (not the EV-1 car) came out, and really only lead acid was around the system_ was designed _with a bypass contactor and actually worked pretty much like coulomb suggested. Just past full throttle on the controller there was a switch on the throttle box to operate a bypass contactor, but since the voltage was limited to 120 volts with lead acid, there wasn't any tire spinning power suddenly unleashed, but you did feel a good kick when the contactor closed. Probably not a good idea now with lithiums!
Mike
www.EV-propulsion.com


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