8 ms·

Is Elon's claim, "the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan", accurate? AFAIK, all the Lithium Ion Ba

by devy 13y ago

Is Elon's claim, "the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan", accurate? AFAIK, all the Lithium Ion Battery electrolytes are flammable (they are pressurized in the battery container too). Depending on the chemistry of the Lithium-ion battery that Model S uses, some (I.E. LFP) are safer than the others, but still, 1% potential? EVs like Chevy Volt, Fisker Karma and even Boeing 787 Dreamliner and UPS/FedEx freight flights had been caught Lithium fires in air before.

cma 13y ago
Wasn't there some controversy about Elon saying the Dreamliner specifically didn't have the right kind of firewalls/compartmentalization and that Tesla could help them?
- toomuchtodo 13y ago
  Yes. http://www.reuters.com/article/2013/01/29/boeing-tesla-idUSL1N0AY11R20130129 http://www.reuters.com/article/2013/01/29/boeing-tesla-idUSL...
Jtsummers 13y ago
In contrast, the combustion energy of our battery pack is only about 10% of the energy contained in a gasoline tank and is divided into 16 modules with firewalls in between. As a consequence, the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan. It seems he's dividing that 10% by 16 and rounding up based on his confidence (presented confidence or real confidence I don't know) in the firewalls.
pja 13y ago
In making that claim he's presumably assuming that the battery design prevents a cascading failure where the failure of one battery module causes adjacent ones to fail in turn. He's also assuming that there's no external factor that could cause all the battery compartments to fail simultaneously. It's partially PR fluff in other words. The total combustion energy of the battery pack is only 10% of that of the petrol tank in a petrol-fueled vehicle partially because the energy density of Lithium-ion cells is significantly less than petrol or diesel fuel, which is why the Model S has half the range of similar conventionally fuelled cars in it's class. I'd also speculate that he's only measuring the combustion energy of the hydrogen that could escape & ignoring any electrical heat generated. The control systems on the batteries ought to cut the connections to the cells if they detect a short of course, but no system is perfect & he's very careful to use the more specific term "combustion energy".
- kbenson 13y ago
  > In making that claim he's presumably assuming that the battery design prevents a cascading failure where the failure of one battery module causes adjacent ones to fail in turn. He's also assuming that there's no external factor that could cause all the battery compartments to fail simultaneously. It's partially PR fluff in other words. Maybe. When the dreamliner battery fire happened, had quite a bit to say regarding batteries and cascading failure. He's surely making some assumptions (such as discounting an external factor as you state), but it's not like he isn't on record asserting they have put some effort into preventing or mitigating this exact problem[1]. [1]: http://www.dailytech.com/Tesla+CEO+Elon+Musk+Says+Boeings+787+Dreamliner+Battery+is+Unsafe/article29781.htm http://www.dailytech.com/Tesla+CEO+Elon+Musk+Says+Boeings+78...
Someone 13y ago
It's a 85kWh battery (http://en.wikipedia.org/wiki/Tesla_Model_S#Specifications http://en.wikipedia.org/wiki/Tesla_Model_S#Specifications). Gasoline is about 12kWh/kg or 9kWh/l (http://en.wikipedia.org/wiki/Gasoline#Energy_content http://en.wikipedia.org/wiki/Gasoline#Energy_content) So, that 85kWh battery, when driving an engine, is equivalent to about 10 liters of gasoline. I guess that's more or less what could get released in a fire (corrections welcome; I don't know what kind of factor that 'effective' could introduce) If that logic stands, to get at 1%, the typical car would have to have 1000 liters of gasoline on board (for the metric impaired: that's over 250 US gallons/over 200 imperial gallons). That, clearly, is unrealistic. Elon may have knowledge of the loading state of the battery, but if so, I think he should have mentioned that. Gasoline tanks aren't 100% full all the time, either.
- leokun 13y ago
  > Gasoline tanks aren't 100% full all the time, either. The less gas a tank has, the more dangerous it could be. It's a common mistake to think a close to empty tank of gasoline is safer than a full one when the reverse may be true because of the fumes. For example: http://www.commerce.wa.gov.au/worksafe/content/safety_topics/hazardous_substances/Additional_resources/Empty_drums_-_potential_bombs.html http://www.commerce.wa.gov.au/worksafe/content/safety_topics...
  - sliverstorm 13y ago
    We're just talking about energy content right now, not damage potential.
  - jlgreco 13y ago
    I'm not convinced of that. If you are worried about the tank going "pop", then a mostly empty gas tank would indeed be more dangerous. However I think the more typical concern is the tank being punctured, leaking, then the leaking gas burning rather than exploding. So basically if you want it to explode hollywood style, then you need gas vapors, but if you want a very bad car fire, then you need lots of gas.

by devy 13y ago

cma 13y ago

Wasn't there some controversy about Elon saying the Dreamliner specifically didn't have the right kind of firewalls/compartmentalization and that Tesla could help them?

toomuchtodo 13y ago
Yes. http://www.reuters.com/article/2013/01/29/boeing-tesla-idUSL1N0AY11R20130129 http://www.reuters.com/article/2013/01/29/boeing-tesla-idUSL...

Jtsummers 13y ago

In contrast, the combustion energy of our battery pack is only about 10% of the energy contained in a gasoline tank and is divided into 16 modules with firewalls in between. As a consequence, the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan. It seems he's dividing that 10% by 16 and rounding up based on his confidence (presented confidence or real confidence I don't know) in the firewalls.

pja 13y ago

In making that claim he's presumably assuming that the battery design prevents a cascading failure where the failure of one battery module causes adjacent ones to fail in turn. He's also assuming that there's no external factor that could cause all the battery compartments to fail simultaneously. It's partially PR fluff in other words. The total combustion energy of the battery pack is only 10% of that of the petrol tank in a petrol-fueled vehicle partially because the energy density of Lithium-ion cells is significantly less than petrol or diesel fuel, which is why the Model S has half the range of similar conventionally fuelled cars in it's class. I'd also speculate that he's only measuring the combustion energy of the hydrogen that could escape & ignoring any electrical heat generated. The control systems on the batteries ought to cut the connections to the cells if they detect a short of course, but no system is perfect & he's very careful to use the more specific term "combustion energy".

kbenson 13y ago
> In making that claim he's presumably assuming that the battery design prevents a cascading failure where the failure of one battery module causes adjacent ones to fail in turn. He's also assuming that there's no external factor that could cause all the battery compartments to fail simultaneously. It's partially PR fluff in other words. Maybe. When the dreamliner battery fire happened, had quite a bit to say regarding batteries and cascading failure. He's surely making some assumptions (such as discounting an external factor as you state), but it's not like he isn't on record asserting they have put some effort into preventing or mitigating this exact problem[1]. [1]: http://www.dailytech.com/Tesla+CEO+Elon+Musk+Says+Boeings+787+Dreamliner+Battery+is+Unsafe/article29781.htm http://www.dailytech.com/Tesla+CEO+Elon+Musk+Says+Boeings+78...

Someone 13y ago

It's a 85kWh battery (http://en.wikipedia.org/wiki/Tesla_Model_S#Specifications http://en.wikipedia.org/wiki/Tesla_Model_S#Specifications). Gasoline is about 12kWh/kg or 9kWh/l (http://en.wikipedia.org/wiki/Gasoline#Energy_content http://en.wikipedia.org/wiki/Gasoline#Energy_content) So, that 85kWh battery, when driving an engine, is equivalent to about 10 liters of gasoline. I guess that's more or less what could get released in a fire (corrections welcome; I don't know what kind of factor that 'effective' could introduce) If that logic stands, to get at 1%, the typical car would have to have 1000 liters of gasoline on board (for the metric impaired: that's over 250 US gallons/over 200 imperial gallons). That, clearly, is unrealistic. Elon may have knowledge of the loading state of the battery, but if so, I think he should have mentioned that. Gasoline tanks aren't 100% full all the time, either.

leokun 13y ago
> Gasoline tanks aren't 100% full all the time, either. The less gas a tank has, the more dangerous it could be. It's a common mistake to think a close to empty tank of gasoline is safer than a full one when the reverse may be true because of the fumes. For example: http://www.commerce.wa.gov.au/worksafe/content/safety_topics/hazardous_substances/Additional_resources/Empty_drums_-_potential_bombs.html http://www.commerce.wa.gov.au/worksafe/content/safety_topics...
- sliverstorm 13y ago
  We're just talking about energy content right now, not damage potential.
- jlgreco 13y ago
  I'm not convinced of that. If you are worried about the tank going "pop", then a mostly empty gas tank would indeed be more dangerous. However I think the more typical concern is the tank being punctured, leaking, then the leaking gas burning rather than exploding. So basically if you want it to explode hollywood style, then you need gas vapors, but if you want a very bad car fire, then you need lots of gas.