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  #1  
Old 03 January 2011, 08:41 PM
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Blow Your Top Electrocuted while towing electric car

Comment: Just heard a story on the radio that some towing companies are
refusing to tow electric cars because a few of the employees have died
from electrocution trying to tow the cars.

Any truth to that?
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  #2  
Old 03 January 2011, 08:58 PM
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There hasn't been any records of people getting electrocuted while extracting people from a wrecked electric or hybrid car (according to this site). I severely doubt that there is any electrical systems located anywhere near the towing locations of any cars electrical or not for safety or legal reasons. Besides - when a car is turned off (in other words when it would get towed), electricity isn't going to be flowing at all.

ETA: My article points this out:

Quote:
Even simply shutting down the car interrupts the flow of power from the batteries to the motor, so the high-voltage cables that connect them are left without power.
ETA: I really doubt that any necessary cables are going to be anywhere near the tow points. These aren't live wires on wheels.

Last edited by diddy; 03 January 2011 at 09:04 PM.
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Old 03 January 2011, 09:25 PM
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It might be possible to be electrocuted while towing a car that had been in an accident if the batteries short-circuited to the frame. Then the tow driver could get electrocuted when he hooks the cables to the tow points on the frame. Pretty unlikely of course.
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Old 03 January 2011, 09:43 PM
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It's pretty unlikley I would say - first we don;t have any recorded incedents of it happening. Second, the manufacturers probably have considered such an event - my article points out that there are several breakers that trip in the event of a crash - most likely the car's power would go off. I also would think that you could just disconnect the battery - something you can train the tow operators to do if they don't know how already.
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Old 03 January 2011, 10:17 PM
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My browser freezes when I try to read Diddy's article. I blame it on those new fangled electrical car contraptions. Dang it.

Anyway, it's my understanding that in electric cars and hybrids, the wheels are turned by electric motors.

So, if the electric motor is not supplied with electricity to turn the wheels, but an outside force makes the wheels rotate anyway, those same electic motors could generate electricity (like when the regenerative brakes are used).

I was wondering if that might be the source of the worry - not the batteries, but electricity generated by the rotating wheels of a car being towed the old fashioned way, with two tires on the ground.

It still seems unlikely to me. It must be fairly simple to have the electric motors default to not engaging with the wheels, like when the car is coasting.

That might be covered in Diddy's article, I don't know.
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Old 03 January 2011, 10:32 PM
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Depends on they type of eletrical motor that the car uses. If the motor uses permanant magnets, then it could theoretically be possible to generate electricity when towing it. But that would mean that there was no clutch or transmission between the motor and the wheels (or that the tow truck driver didn't disengage it). If the motor doesn't use permanant magnets, then there is no way to spontaneously generate electricity from towing the car.
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Old 03 January 2011, 11:07 PM
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Even so, I doubt that there is much risk a tower could face - it doesn’t take them much time to hook a car to their truck - certainly not enough where the regenerative breaking or other systems to kick in while the car is turned off.
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  #8  
Old 04 January 2011, 04:32 AM
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Two misconceptions about electrocution:

1. You can't be electrocuted by touching one contact. There must be contact with two conductors with a potential difference of at least 50 volts between them. At higher voltages, one of the conductors can be the ground or a concrete floor.

2. Electrocution does not always produce death. It means being burned by electric current. I have been electrocuted, and I am still alive. I burned a finger once when an impatient person wanting to play a video game turned the breaker back on while I was working on the circuit.

In the case of electrocution from an electric car, contact must be made simultaneously with BOTH the car frame (connected to one side of the battery) AND something connected to the other (hot) battery terminal. Touching the car frame alone will not cause a shock.

Birds can perch on high voltage lines, because they are touching only one wire at a time.

The most likely cause of electric shock from a damaged electric or hybrid car would come from the tow hook momentarily coming in contact with the hot battery cable, and the operator touching both the tow chain or bar and the car frame at the same time.

If the ground and the operator's shoes are wet, they might together provide one of the connections, if a broken battery cable is touching the pavement..

If contact occurs on the grounded frame, and also anywhere along the wire connecting the hot battery terminal to the power switch and throttle controls, a shock can occur even if the switch is off,

If the car has broken into multiple pieces, one piece might be connected to or in contact with the hot battery terminal, while another piece is connected to the grounded terminal. Touching both pieces at the same time could produce a shock.
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  #9  
Old 05 January 2011, 02:32 AM
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Quote:
Originally Posted by Troubleshooter View Post
There must be contact with two conductors with a potential difference of at least 50 volts between them.
A 12V car battery will give a heck of a shock if the skin is penetrated, you don't need 50V. Worse case scenario is that a typical car battery could provide a fatal shock.

Most car mechanics have experienced a "skin breach" shock at 12V. Usually it happens when you have one hand resting on the frame and grab a braided hot wire with the other. One of the braid strands pokes through the skin and
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