I would hypothesize that a lithium ion battery pack would respond in a different manner than a conventional fuel tank. So, perhaps the point of impact would need to be addressed as well as integrity of the battery pack after impact. With fuel, one can spot a leak; with a battery pack, the damage may not be apparent at first--witness the two incidents with battery packs on the Volt catching fire some period of time after the test.
Apparently the Chevy Volt is having some problems with side impact crashes. The weird thing is that the fires don't start for 3 to 7 days LATER. Quite a bit different than the old Ford Pintos which could erupt in a fireball immediately after a rear end crash,
Fire fighters are now being trained how to handle and "disarm" electric powered vehicles.
Well the tests are different for electric vehicles in the UK.
This was covered in another thread somewhere commenting on the crash of a G Wiz in London.
It seems, in the interests of being "green" the tests are a whole lot different.
A fatal accident is reported here..
It appears the crash test people thought the G Wiz too dangerous even for their crash test dummies.
While logic dictates that all road vehicles should pass the same crash tests, especially tests replicating being struck by another vehicle, It would seem apparent that bicycles and motor bikes would fail miserably in tests designed for cars.
That is the main reason I mostly ride my bicycle on footpaths. Also financially, the risk/cost of a fine vs the risk/cost of a collision involving a car stacks up in favour of riding on footpaths.
It would seem reasonable from comments above that a sitting time of 1 week be applied to the tests for electric cars. I guess an internal short in the battery is even possible in a petrol or diesel fuelled car, just to a lesser extent due to less batteries and lower voltages.
Regards
Pat
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There will need to be standards for lithium-ion batteries used in cars. Should a collision manage to damage or short-out even one cell then it can dump it's stored energy resulting in a cascade reaction in surrounding cells.
The standard for cell failure is the nail penetration test. See the video:
I don't know what kind cells more recent electric vehicles are using but the Telsa uses 6,831 cylindrical cells with a total of 56 kWh of stored energy.
Some more recent battery technologies are not quite so destructive in their failure modes, such as lithium iron phosphate or lithium nanophosphate.
The G Wiz had some pretty primitive batteries and does now offer a Lithium otpion.
I think they had lead acid as a first option.... Li Ion comes with the G Wiz L-ion
The Volt problem is caused by some battery coolant leaking out. When it dries out after a week or so, it switches from being an insulator to a conductor as a result of crystalization. Thus redesign of battery and battery tray to reduce likelyhood of short circuit is in order.
For gas vehicle tests, fuel is drained out after the test is certified as complete. In the case of the Volts, they just towed them away (fully charged) without tapping off the battery or powering it down. Funny that a gas car crash test would likely leak out some fuel or vapor after sitting for a few weeks and cause the same ruckus. If they had left the radio on in the Volts, nothing might have happened.
Anybody consider as a separate issue that, as the car ages, coolant leaks are not all that uncommon... To have a battery cooling system design that allows leaking coolant to get onto a circuit board designed without adequate secondary circuit protection an issue all by itself.
Contaminants getting on circuit boards designed without regard to preventing escalation of failure to the point of fire has happened in a number of applications.
A number of home appliance fire issues are the result of similar failure mechanisms.. For example a widely sold dishwasher that had problems with leaks from the rinse agent reservoir leaking down onto a circuit board and starting a significant fire.. In the recall notice for this problem, it was documented that in this instance the fire accelerated to the point that houses were burned down..
Circuit board fires and design evaluation methods prevent (we called it secondary circuit protection) have been for a long time..
I would say Volt fires, (and applicance fire issues) raises the question as to how much analysis was done in the design phase to ensure such failure mechanisms were not in the design.
It doesn't take much imagination if you consider the resins commonly used in glass/epoxy circuit boards, types of components (e.g. carbon resistors, that when overloaded, can glow at red temperatures, and ABS plastics in the vicinity, that it all can become a nice smoke/fire initiator if protection is not inherent in the design.
Very briefly a design analysis/test cycle looks at the energy sources present and the components/mechanisms in the design to open circuit the failure following a time/current limit profiles well known in the industry to stop a short/low resistance failure from escalation to fire.
Analysis of the adjacent materials with regard to their ignition points and ability to contain a fire is another important aspect.
In a joint project with Motorola many years ago they introduced me to a process called "Failure Mode Effects Analysis"
>>>Now why would you design a washing machine with the circuit boards at the bottom? Surely you'd try and keep them high and dry? <<<
The usual explanation, so far as I can tell, is that the people who actually knew how to design a washing machine, and how not to, became 'too expensive', and were replaced with more affordable recent graduates, who have never done their own laundry, or fixed a broken anything.
Well, it's probably not Casa Grande, AZ aiport, and probably not ciglitazone, coarse-grain zone, CowGirlZen, Caaguazu, Consulting Gruppe Zürich AG, China Water Filling Machine, or any of dozens of other possibilities.
I think Greg is talking about the height of the center of gravity above the base plane, which would affect overturning resistance, a subject of interest to 'Elf 'n Safety folks, but I'm not sure why Greg is being coy about it.
It's certainly a good reason to put a washing machine's motor as low as possible, but circuit boards and even their power supplies grow smaller and lighter every year, so you probably can't move the CGZ by more than a few mm by moving all of the electronics up or down.
One might be tempted, however, to do it by omitting the usual control cupola above the machine shell, and putting everything in the base, in the interest of a cost reduction by means of eliminating an entire major piece of sheet metal or plastic.
Don't they drain the fuel tanks when crash testing cars?
The G-Whiz is a quadricycle hence does not need to comply with crash test regulations. My Friend did the Top Gear G whiz crash test.
