6 ms·

Wish I had your crystal ball. With improvement, I was referring to the complexity of cutting someone out of a Tesla and all the no-cut zones that could electro

by abalone 13y ago

Wish I had your crystal ball. With improvement, I was referring to the complexity of cutting someone out of a Tesla and all the no-cut zones that could electrocute passengers, emergency responders, even guys towing wrecks. You're right, there is no real safety record yet.

lutusp 13y ago
> With improvement, I was referring to the complexity of cutting someone out of a Tesla and all the no-cut zones that could electrocute passengers, emergency responders, even guys towing wrecks. As an electrical engineer with spacecraft experience, I can say that a car like the Model S isn't likely to electrocute anyone. While extracting someone from a wreck, emergency workers use tools like the "jaws of life", strong metal pliers meant to quickly snip a car's body apart. When a tool like this cuts into an electric car, if it should slice through a power cable, in most cases the tool would short the cable to the car's chassis, thus grounding it and tripping the safety links that are integral to the battery pack. This means the car will become inoperative, but it doesn't mean anyone will get electrocuted. I think the above will be the outcome in the vast majority of cases. Compare this to the plight of someone sitting in a wrecked gasoline-fueled car.
- abalone 13y ago
  Hi there. Go ahead and watch this video from Tesla about how to cut someone out of a Tesla. The very first step is to cut the circuit like you say, but there are a few things you overlooked. Much of the video is concerned with instructing responders how to cut around components that may remain electrified such as the converter and capacitors which, in Tesla's own words, present a "serious hazard of shock" because "they can release up to 400 volts in just an instant." http://www.youtube.com/watch?v=ntK3rvVl2Qw http://www.youtube.com/watch?v=ntK3rvVl2Qw
  - ash 13y ago
    Do other car manufactures provide such videos?
    - goatforce5 13y ago
      I know a paramedic in rural Australia. They get taken to local car dealers to get safety training with electric cars. As I understand it it's done on a per-model basis, but that wont really work as an increasing number of electric car models end up on the roads. I'm not sure if this is done all over the state/country, or if it's the one local dealer being friendly with the local emergency services.
  - sergiosgc 13y ago
    Nitpicking, I know, but releasing 400 volts means nothing. Current kills, tension does not. It all hinges on the internal resistance of the power source.
    - moocowduckquack 13y ago
      That and time. You could get hit with high volts and current, but still be fine if the exposure is short. I have had a few 240v mains shocks on high current fuses, but they were all pretty quick and I had nothing but very slight burns and sore muscles for about ten minutes. However, there is definitely a risk here, albeit what appears to be a manageable one. Perhaps there could be some use in building volt meters that glow into gloves for emergency responders to help mitigate some of the risk.
    - iyulaev 13y ago
      Perhaps it would be even better to say, "power transmission kills."
    - rthomas6 13y ago
      Well, also the resistance of the load.
    - abalone 13y ago
      Voltage means A LOT. A regular 12V car battery is a perfect proof: it has enough current to kill you, but at only 12V it doesn't overcome your body's resistance much under most circumstances. 400V can overcome your body's resistance no problem. And obviously an EV has a crap ton of amperage as well.
- James_Duval 13y ago
  Would the tools used not be developed? I would've assumed the production of specialised tools for electric cars would be a priority once they become popular.
  - jbellis 13y ago
    Presumably, avoiding electrocution of the passenger being extracted is also a goal.
    - James_Duval 13y ago
      I don't understand your response, is this not what the specialised tools would be primarily designed for?
      - JshWright 13y ago
        What sort of tools are you envisioning?
        moocowduckquack 13y ago
        maybe insulated ones
        JshWright 13y ago
        Insulating the tools isn't really the issue. There's already a fair amount of insulation between me (the tool operator) and the business end of the tool. The problem is, we're cutting through and crushing various bits of the car that weren't really designed to be indiscriminately cut into (which is why training is so important). Both rescuers and victims have been seriously injured and killed when extrication activities turned potential energy stored in the car into kinetic energy. Air bag deployment systems, seat belt pretensioners, even the little hydraulic tubes that hold your trunk open and be extremely dangerous if their energy is released in an uncontrolled way. So you can understand why we're a little leery of 85 kWh of potential energy sitting under the car... Here's an example of airbags being deployed when the SRS controller was crushed with a hydraulic spreading tool. https://www.youtube.com/watch?v=yDSksTztHJk https://www.youtube.com/watch?v=yDSksTztHJk Two firefighters were injured in that incident (one of them seriously).
- tmzt 13y ago
  Would an independent accelorometer in the battery assembly shut of the power when the car is involved in a collision? It wouldn't make sense for it to be dependent on a link from the airbag sensors, it would have to be local to the power plant.

by abalone 13y ago

lutusp 13y ago

> With improvement, I was referring to the complexity of cutting someone out of a Tesla and all the no-cut zones that could electrocute passengers, emergency responders, even guys towing wrecks. As an electrical engineer with spacecraft experience, I can say that a car like the Model S isn't likely to electrocute anyone. While extracting someone from a wreck, emergency workers use tools like the "jaws of life", strong metal pliers meant to quickly snip a car's body apart. When a tool like this cuts into an electric car, if it should slice through a power cable, in most cases the tool would short the cable to the car's chassis, thus grounding it and tripping the safety links that are integral to the battery pack. This means the car will become inoperative, but it doesn't mean anyone will get electrocuted. I think the above will be the outcome in the vast majority of cases. Compare this to the plight of someone sitting in a wrecked gasoline-fueled car.

abalone 13y ago
Hi there. Go ahead and watch this video from Tesla about how to cut someone out of a Tesla. The very first step is to cut the circuit like you say, but there are a few things you overlooked. Much of the video is concerned with instructing responders how to cut around components that may remain electrified such as the converter and capacitors which, in Tesla's own words, present a "serious hazard of shock" because "they can release up to 400 volts in just an instant." http://www.youtube.com/watch?v=ntK3rvVl2Qw http://www.youtube.com/watch?v=ntK3rvVl2Qw
- ash 13y ago
  Do other car manufactures provide such videos?
  - goatforce5 13y ago
    I know a paramedic in rural Australia. They get taken to local car dealers to get safety training with electric cars. As I understand it it's done on a per-model basis, but that wont really work as an increasing number of electric car models end up on the roads. I'm not sure if this is done all over the state/country, or if it's the one local dealer being friendly with the local emergency services.
- sergiosgc 13y ago
  Nitpicking, I know, but releasing 400 volts means nothing. Current kills, tension does not. It all hinges on the internal resistance of the power source.
  - moocowduckquack 13y ago
    That and time. You could get hit with high volts and current, but still be fine if the exposure is short. I have had a few 240v mains shocks on high current fuses, but they were all pretty quick and I had nothing but very slight burns and sore muscles for about ten minutes. However, there is definitely a risk here, albeit what appears to be a manageable one. Perhaps there could be some use in building volt meters that glow into gloves for emergency responders to help mitigate some of the risk.
  - iyulaev 13y ago
    Perhaps it would be even better to say, "power transmission kills."
  - rthomas6 13y ago
    Well, also the resistance of the load.
  - abalone 13y ago
    Voltage means A LOT. A regular 12V car battery is a perfect proof: it has enough current to kill you, but at only 12V it doesn't overcome your body's resistance much under most circumstances. 400V can overcome your body's resistance no problem. And obviously an EV has a crap ton of amperage as well.
James_Duval 13y ago
Would the tools used not be developed? I would've assumed the production of specialised tools for electric cars would be a priority once they become popular.
- jbellis 13y ago
  Presumably, avoiding electrocution of the passenger being extracted is also a goal.
  - James_Duval 13y ago
    I don't understand your response, is this not what the specialised tools would be primarily designed for?
    - JshWright 13y ago
      What sort of tools are you envisioning?
      - moocowduckquack 13y ago
        maybe insulated ones
        JshWright 13y ago
        Insulating the tools isn't really the issue. There's already a fair amount of insulation between me (the tool operator) and the business end of the tool. The problem is, we're cutting through and crushing various bits of the car that weren't really designed to be indiscriminately cut into (which is why training is so important). Both rescuers and victims have been seriously injured and killed when extrication activities turned potential energy stored in the car into kinetic energy. Air bag deployment systems, seat belt pretensioners, even the little hydraulic tubes that hold your trunk open and be extremely dangerous if their energy is released in an uncontrolled way. So you can understand why we're a little leery of 85 kWh of potential energy sitting under the car... Here's an example of airbags being deployed when the SRS controller was crushed with a hydraulic spreading tool. https://www.youtube.com/watch?v=yDSksTztHJk https://www.youtube.com/watch?v=yDSksTztHJk Two firefighters were injured in that incident (one of them seriously).
tmzt 13y ago
Would an independent accelorometer in the battery assembly shut of the power when the car is involved in a collision? It wouldn't make sense for it to be dependent on a link from the airbag sensors, it would have to be local to the power plant.