# Sinopoly battery torture



## lithiumlogic (Aug 24, 2011)

A good thing it is too - we're putting these batteries in the crumple zone of our vehicle, where they are going to get rapidly crushed or torn apart in an accident. The one dissapoinment is we didn't see a simulation of this kind - impact by a heavy and fast-moving object, though i see no reason why they'd fail.

I'm interested in the dynamics of why one cell type may go into thermal runaway, and another not, and whether cell safety can be maintained as energy densities increase.

One comment I've heard in favour of LiCo chemistry is that if only charge them to LiFePO4 Wh/Kg levels, they don't explode either.

The main safety advantage of iron phoshpate seems to be the higher temperature at which thermal runaway starts.

I'm trying to model what happens in that video, when they create an internal short circuit by shooting it full of 9mm rounds :

1. Heat production occurs due to an electrical short.

Watts produced = Current x Voltage

The low internal resistance of these cells is a disavantage here, since it means more current


2. Heat is removed by the boiling of electrolyte (the white steam?). The loss of eletrolyte will eventually curtail the cell's ability to produce current and heat.

Factors 1) and 2) are balanced such that the cell never reaches runaway.


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## dtbaker (Jan 5, 2008)

wow..... shooting at the battery, interesting way to create internal short and demo to military sales I guess? Sounds like they're having an office party in the background. 

I would much prefer to see an independent lab test of cycle life at 3C discharge/.1C charge compared to CALB.....


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## Ziggythewiz (May 16, 2010)

I dunno, I thought the battery didn't look too great gettin shot. That was a fair bit of smoke or steam or whatever that was coming out, and it wasn't even connected to anything. It's not like anyone went and touched it to show how safe it was. Plus sitting in a bed of snow would help with any thermal runaway issues.

I'd rather see them shoot at a whole pack of em or whack it with an suv as logic mentioned...while running at 400 amps. I don't see much value in shock testing a battery in idle condition.


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## icec0o1 (Sep 3, 2009)

The only way li batteries catch on fire is when they're overcharged past 4.2v for a period of time which causes a hydrolysis of the electrolyte into very flamable gasses and swells up the cells. Those gasses then can catch on fire. It's extremely unlikely if not impossible that any other condition would catch a lithium battery on fire.


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## lithiumlogic (Aug 24, 2011)

I think getting shot or nail penetration is worst case , the bullet makes a hole in the separator allowing anode and cathod to make contact (short circuit) assuming it doesnt actually lodge in the battery and become the short circuit conductor itself.

On a PDF (by A123 systems?) they did abuse tests on their cell vs a typical lithium cobalt laptop cell including a crush test. They said crushing slowly with a hydraulic test was a more severe test as rapid crushing would have a tendency to quench the cell. I suppose if the container splits and all the electrolyte is forced out under pressure, there isn't going to be much left to make a short circuit current, ditto if it's torn apart and unwound.

As you say though a whole pack of batteries tightly stuffed together in an insulated box is a more worrying scenario.. if the heat has nowhere to go, runaway might be reached, and each cell could set off it's neighbour.

Also what if you got 30 series strings of 2 in parallel, and one gets penetrated by a nail? This is a worse short circuit condition, because unless you have fusing between each cell, the cell it is paralleled with will dump current into the shorting cell. Twice the energy being dissapated by the same mass of battery... doesnt sound good.


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