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  #31  
Old 08-23-2012, 07:34 AM
drgrieve drgrieve is offline
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Default Re: Useable power

I drive a 85kw peak ICE car. Not that it would push that out now as it's 15 years old.

It weighs around 3000 lbs with me in it with full tank.

I've driven it over 100 mph with no problem, I rev it from the stop lights and change at 5000 rpm to get nowhere first.

So I would agree with OP that a 80 kw peak EV is absolutely fine for a commuter car.

But I don't grin.
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  #32  
Old 08-23-2012, 09:10 AM
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McRat McRat is offline
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Default Re: Useable power

Quote:
Originally Posted by DIYguy View Post
I think the problem with Lipoly (not lifepo) is that the metal oxide provides the oxygen during thermal run away. Excluding air, or surrounding with halon, will do nothing to stop it.
Best guess:

Nothing reactive is going to work well on a runaway pack. That needs to be proactive. A system should be in place to shut it down before the temperature becomes unsafe, not after.

Normal suppression for metal fires is "D" class powders, but they would do very little except make it more dangerous by insulating the pack with a hard shell. Think firecracker.

#1 is to get the driver out alive. #2 is to minimize damage.

To get the driver out, a firesuit and Halon would be the best choice. If the fire was not a runaway battery, it would do job #2 without damaging the equipment.

Flooding the individual cells with water will stop a runaway pack. You can't carry enough water onboard to handle >200lbs of batteries though. You need a firetruck. And you'll do some unintended damage with water.

Aqueous foam is not a good choice, nor are CO2 systems. They don't pack nearly the punch of the same weight of Halon.

I will probably test Halon (used correctly) on a runaway when I get around to it, but we are talking about a $1000++ test. I think the FAA testing was invalid for EV's, since it involved just small, low voltage battery packs, not high amp, high voltage situations. They did not attempt to use the cooling effect of 1301, and only used short bursts of 1211, not sustained. However, the FAA still requires Halon on board last I heard.
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  #33  
Old 02-22-2013, 02:57 PM
toyolla2 toyolla2 is offline
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Default Re: Useable power

It seems rather unusual to consider the choice of motor to protect the battery pack. Each has a job to do and a set of specifications and needs individual protection. You can make judgment calls to balance risk of component degradation with maximum possible performance, but I'd want the ability to get everything I could (without blowing up) rather than be limited to what is most efficient and least damaging.



Months later this statement would seem to be prescient of the problems that Nissan has been having in the desert climes of Arizona where an independant range test was conducted. A route was run which navigated through several interchanges while maintaining a 60mph average speed for 83 minutes. I find it hard to believe the driver could avoid the need to pump the Leaf's 80Kw motor a few times to the detriment of the battery ? A battery which was already being cooked through its underside while passing over a continuous strip of asphalt , baking hot from the mid day sun. It is likely that a 40Kw motor could have completed the course with less energy expenditure, I can't help feeling.

Last edited by toyolla2; 02-23-2013 at 01:22 AM. Reason: Seperation of statement and rebuttal
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