Does your insurance company allow you to keep one liter of gasoline in your garage? It has the same energy content as the Powerwall, is insanely flammable, is frequently implicated is home fires, and regularly causes human deaths.

(Ok, a burning lithium battery will release more energy than its storage capacity, but I'm not finding a nice reference, Tesla knows all about containing cells to prevent chain reactions, and one liter of gasoline is still enough to burn down your whole house.)

Gas fumes are very flammable, but the gasoline itself will flow down and out of my garage, and the fire would be very easy to contain with a simple garden hose.

A gas can also will not light on fire just because it gets hit with a car. It would take malicious use of a gas can -- splashing it on a wall and then lighting it on fire -- to match the default configuration of a Powerwall.

I don't think you use the same gasoline as the rest of the planet if that's your experience.

You ever try to put out a gasoline fire with a garden hose?

While you are correct, you can at least snuff out a gasoline fire.

Lithium fires do not require oxygen, so your typical Class ABC fire extinguishers won't actually work on it. You need a class D (dry powder) extinguisher, which is very rare and expensive.

While true for lithium fires, a venting lithium-ion battery is not a typical lithium fire.

According to the MSDS for lithium ion batteries, fires involving them can be extinguished with a typical ABC fire extinguisher.

Lithium batteries (not the rechargeable kind) are the ones that need a class D extinguisher.

Edit:

> CO extinguishers, halon or copious quantities of water or water-based foam can be used to cool down burning Li- ion cells and batteries. Do not use for this purpose sand, dry powder or soda ash, graphite powder or fire blankets.

> Extinguishing media Use water or CO2 on burning Li-ion cells or batteries

http://www.uscg.mil/hq/cg4/cg432/docs/msds/MSDS_LiIon.pdf

Using water on an electric fire sounds like a dumb idea to me. But yeah, the MSDS does seem to say that...

A venting lithium ion battery isn't usually an electrical fire.

And what of all the molten wires that _were_ charging said battery?

Overcharging a battery isn't the only way to cause it to vent :)

Obviously there should be a physically separate circuit for cutting off power in the event of catastrophe. That's pretty much rule-of-thumb for large li-ion battery banks.

> Lithium fires do not require oxygen

I thought fire is by definition a combustion reaction, meaning some kind of material reacting with oxygen. What's fire, then? (I feel like a little kid, having to ask that...)

Generally, a fast exothermic reaction. Oxygen may be the most popular oxidant, but not the only one. Lots of stuff burns in pure chlorine gas, for instance.

Some substances bundle together their oxygen source (think of rocket fuel, or napalm), so they don't need to consume it from air.

It's possible for something to burn hot enough to split water molecules apart. I don't know if lithium metal qualifies, but that could be what the MSDS is referring to.

It's common advice not to leave rags that have gasoline on them sitting in your garage because in enough heat the fumes from the evaporating gasoline will combust. Gasoline is very volatile, we've just gotten fairly good at managing it.

Or a vapor reaching an open flame. Common source of human immolation.

edit: my karma https://news.ycombinator.com/reply?id=9471929&goto=threads%3...

edit: my karma http://i.imgur.com/rjNrXTc.gifv

Moderation is pretty weird in this thread. I got voted down for pointing out that the US power grid is likely to experience problems when entire residential neighborhoods full of Tesla owners try to charge their Model S at once.

I don't think many people around here understand (a) just how efficient gasoline really is at storing energy, and (b) just how much energy is used by a typical passenger car.

Talk to your insurance people. Usually when you have expensive items, you can get a specific rider for it.

For example, a friend had a rack with about $80k of servers in his basement a few years ago. I believe he paid an additional $400 for coverage.