Inside a Tesla Model S Battery Pack (opens in new tab)

Modern high volume, quality focused manufacturing will often prioritize ease of assembly over elegance in design. Fewer, simpler steps make for fewer defects and greater product consistency. It's the whole "lean manufacturing" ideal at play, done right it will lower costs and improve quality to a point that you can splurge on a little engineering elegance such as a small-volume hybrid model capable of being assembled on the same line as your high-volume offerings. Tesla doesn't have to worry about this for now as they compete in a high-margin segment of the industry and they are trying to set a benchmark of excellence that will create demand for their products.

A real world example I've seen in person is the Nissan Leaf. The battery is designed to be as safe as possible for handling by a line worker and that allows Nissan to produce the Leaf at the exact same time as plain vanilla Altimas are rolling down the line. If you ever take a tour of their Smyrna, TN plant you'll see 1 line with a 9 or 10 Altimas interspersed with a Leaf every once in a while. It's smart engineering at a production-level viewpoint as a "worse" battery allows an entirely different product to be produced with minimal production overhead.

The biggest issue is vibration loosening a connection in the longer term but there are plenty of time-tested ways to avoid that from happening.

Even fork lift battery packs (which can carry immense currents) are still built using the crimp terminal/bolt through method.

The DC damage is a condition called 'muscular tetanus'. The main risk with AC at medium voltages (say 40 to 250 V) is that your heart goes haywire. Though those voltages could easily kill you too.

Yes, you should always be careful. But DC is most definitely more dangerous at the same voltage once you get over 48 V DC (the so called 'safe voltage', but that's a misnomer because under the wrong conditions voltages lower than that can still be fatal). The critical component by the way is current not voltage. Voltage really doesn't kill but current will. AC voltages are typically reported RMS, whereas with DC the 'peak' is also the average. Assuming the DC supply can produce as much current as the AC supply.

Being shocked by neither is good. But the choice between 200V DC and 200V AC is a fairly easy one for me and I've been shocked multiple times by both during my very long time of taking stuff apart and fixing things (yes, I try very hard to avoid that). The AC ones were mostly non-events, the DC ones were (even at lower currents) things to remember years later. Quite possibly that's not correlated with safety but it is definitely a data point (or rather several of them). Avoiding being shocked is a very good way of never having to find out how accurate this all is. One particularly memorable incident was hooking myself accidentally to the HV supply of an old tube radio. Don't do that. And be extremely careful with capacitors and DC batteries, they can supply a ton of current long enough to kill you. HV transformers much less so. (At least, the ones that you would normally encounter outside of industrial gear). And I suspect that the internal resistance of those supplies has a lot to do with whether you're going to be dead or writing about your experiences because it has a very direct impact you the current resulting. HV AC supplies that will supply very high current are hard to find, usually are transformers with relatively thin secondary windings. A battery pack like this is made to supply 100's of Amps at 100's of volts. That's lethal, make no mistake about that.

That battery bank cost $7200, 2005 or so prices.

More than you ever wanted to know:

http://www.allaboutcircuits.com/vol_1/chpt_3/4.html

Apparently the DC current required is 10 times higher to do comparable damage than the AC current. This is totally at odds with both my first-hand experience and a ton of interaction with professionals. So I'm a bit confused now, there is a whole pile of literature out there that says one thing and then the wikipedia page claims the factor of 10 going the other way, citing a book that I don't have access to.

The fact that the electrical chair is AC was possibly a hint, but the electrical chair was developed during the 'current wars' by the AC proponents. (I'm not sure if they tried to convey the idea that AC was more dangerous that way, it seemed to have been an ill thought out decision from a marketing point of view.)

I'll keep looking and reading to see if I can find an authority that decisively claims either the one or the other.

The factor of 10 seems hard to believe, to generate a 30 mA current through a human body at 230VAC would become 2300V DC for a 300 mA current through that same body (per Ohms law), that's ~800 Watts delivered versus ~80.

2300V 300mA sources are hard to come by but a 600V DC source that can do only a few mA will blow you clear across the room, which makes me wonder what would happen if you happened to interact with a source that is capable of substantially more than that. This would also mean that a 300V DC source such as that battery pack should be perfectly safe to work with but I don't believe that's true for even a moment.

So, my apologies for the unsourced rejection of your claim, to be continued.

If a cell burns it is going to take out its neighbors anyway.

Or they could start to do something similar to LiFePo4 which will not burn.

I know it's kind of a losing battle, but "publicly available" does not mean "in public domain".

From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though.

Any ideas on what "special chemistry" they are using?