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Comment by linsomniac | Hacker News Reader

If even half of these amazing battery technologies had come true, my car would be driven by a D cell battery.

But I'm ok that it hasn't, because I once heard a battery chemistry guy say that "the higher capacity a battery is the more it resembles a bomb." I can't find the reference any more, but with all the Samsungs and Teslas catching fire, it rings true.

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> the higher capacity a battery is the more it resembles a bomb

A battery is a package containing the reagents necessary for a highly energetic reaction. A bomb is a package containing the reagents necessary for a highly energetic reaction. A high-capacity battery is effectively a bomb, pretty much by definition.

Actually a bomb is something that is programmed to detonate intentionally under certain conditions. There are plenty of other similarly energetic chemicals around the house, like gas in cylinders. The problem with some batteries is, unlike a bomb, the detonation conditions are hard to control. Luckily battery ignition, as enegetic as it is, is low velocity.

Fair, I should have said "an explosive", not "a bomb."

This sounds reasonable but I think it's actually pretty silly. In physics everything is at some high energy level rolling doesn't to some lower state. Your body has tons of energy. If we threw you into the right sort of fusion reactor or dropped you down a giant well you'd release massive amounts of energy.

It's not about "high energy" "low energy" or even "by definition an explosive" it's about how likely and favorable the pathway to releasing that energy in a bad way is. Just because you can release it slowly doesn't mean you can release it quickly. Some radioactive materials have lots of energy and a long Half-Life, try making a bomb out of them. It is not a simple question it's a lot of chemistry physics and engineering to answer.

These have not much to do with attempt at increasing power density, but everything to do with particle contamination during the manufacturing process.

They have everything to do with increasing power density. By definition power density is potential energy and when you release that energy you get waste heat.

The capacity is relevant to the intensity of the event, but the reason the event occurs has nothing to do with capacity.

The probability of an event could be related to density. High chemical density possibly required for capacity could mean higher gradients which also could have implications on not only intensity of an event, but also on its probability.

> with all the Samsungs and Teslas catching fire, it rings true.

Are there really a lot of Samsungs catching fire though, in the grand scheme of things?

More than the teslas I think ;)

> "the higher capacity a battery is the more it resembles a bomb."

You mean like gasoline?

Right but worse when batteries contain the “oxidizer”. If the battery uses atmospheric oxygen (e.g. as with hydrogen fuel cell vehicles) then it’s exactly like gasoline.

Or even a flywheel. Any energy storage device is going to be energetic when things go wrong. One of the many challenges is in assessing and managing the risk of such an outcome.

Gasoline only explodes under very specific environmental conditions, otherwise it just burns.

One could say the same about lithium :).

When was the last time you read about a Car carrying tank of fuel sudden burst into frame?

When was the last time you read about battery explosion?

I can't think I've heard of an actually battery explosion yet, just people using the word "explosion" to mean burning or expanding.

U.S. fire departments responded to an estimated average of 152,300 automobile fires per year in 2006-2010. These fires caused an average of 209 civilian deaths, 764 civilian injuries, and $536 million in direct property damage.

Facts and Figures

Automobile fires were involved in 10% of reported U.S. fires, 6% of U.S. fire deaths. On average, 17 automobile fires were reported per hour. These fires killed an average of four people every week. Mechanical or electrical failures or malfunctions were factors in roughly two-thirds of the automobile fires. Collisions and overturns were factors in only 4% of highway vehicle fires, but these incidents accounted for three of every five (60%) automobile fire deaths. Only 2% of automobile fires began in fuel tanks or fuel lines, but these incidents caused 15% of the automobile fire deaths. https://www.nfpa.org/Public-Education/By-topic/Property-type...

Thank you for being the only person willing to do research in these threads.

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