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A mechanic working on a car, with enough juice to fry him, and no way to separate the battery from car? I guess a full discharge first. But what about your ac

A mechanic working on a car, with enough juice to fry him, and no way to separate the battery from car? I guess a full discharge first. But what about your accident, and the jaws of life? Will they conduct? Will the wrenched apart car have conductive edges?

shadowgovt 6y ago
Interestingly, these are actual concerns that firefighters have regarding both Teslas and self-driving cars. The relevant companies put out explainers and training videos on how to do a rescue in these vehicles. In the Teslas, the power system is shunted through a single disconnect point... Cutting that line isolates the battery from the rest of the vehicle. In Waymo cars, firefighters needed to be made aware that high-power electrical conduit and liquid cooling channels go up through the pillars, which are usually empty of energized components or contain only low-power channels (for things like overhead lights).
- bmurphy1976 6y ago
  That's interesting. I never considered this to be a problem but it makes sense. This could be quite challenging if every car manufacturer does something different, but I suspect over time just like with ICE cars they'll iterate towards some local optimum and things start to be very similar.
  - omegaworks 6y ago
    >I suspect over time just like with ICE cars they'll iterate towards some local optimum and things start to be very similar. This doesn't happen organically. Manufacturers were happily iterating toward a different optimum before regulation forced their hands. https://www.nytimes.com/2015/11/27/automobiles/50-years-ago-unsafe-at-any-speed-shook-the-auto-world.html https://www.nytimes.com/2015/11/27/automobiles/50-years-ago-...
    - bmurphy1976 6y ago
      That's not really what I mean though. I'm well aware that without regulations short term incentives and optimization can lead to bad outcomes. What I mean is something along the lines convergent evolution where certain designs keep re-appearing because they just work better than the rest.
elihu 6y ago
That's pretty much the status quo for EVs now; the batteries are hundreds of volts and you can't easily remove it. Draining it isn't an option either, as it damages the battery to be fully discharged. So, you have to work on the car with a live voltage source present. I'm not sure if most modern EVs have manual disconnect switches on the main power cables where they meet the batteries or if you're just expected to wear rubber gloves and use non-conducting wrenches to unbolt the cables. I'd expect any modern EV will at least have contactors to connect the battery to the motor controller (these are basically electrically actuated switches, like a mechanical relay), which will be disabled when the car is off. In general, though, I'd expect the main power cables to be something that doesn't need maintenance and mechanics can generally steer clear of.

shadowgovt 6y ago

Interestingly, these are actual concerns that firefighters have regarding both Teslas and self-driving cars. The relevant companies put out explainers and training videos on how to do a rescue in these vehicles. In the Teslas, the power system is shunted through a single disconnect point... Cutting that line isolates the battery from the rest of the vehicle. In Waymo cars, firefighters needed to be made aware that high-power electrical conduit and liquid cooling channels go up through the pillars, which are usually empty of energized components or contain only low-power channels (for things like overhead lights).

bmurphy1976 6y ago
That's interesting. I never considered this to be a problem but it makes sense. This could be quite challenging if every car manufacturer does something different, but I suspect over time just like with ICE cars they'll iterate towards some local optimum and things start to be very similar.
- omegaworks 6y ago
  >I suspect over time just like with ICE cars they'll iterate towards some local optimum and things start to be very similar. This doesn't happen organically. Manufacturers were happily iterating toward a different optimum before regulation forced their hands. https://www.nytimes.com/2015/11/27/automobiles/50-years-ago-unsafe-at-any-speed-shook-the-auto-world.html https://www.nytimes.com/2015/11/27/automobiles/50-years-ago-...
  - bmurphy1976 6y ago
    That's not really what I mean though. I'm well aware that without regulations short term incentives and optimization can lead to bad outcomes. What I mean is something along the lines convergent evolution where certain designs keep re-appearing because they just work better than the rest.

elihu 6y ago

That's pretty much the status quo for EVs now; the batteries are hundreds of volts and you can't easily remove it. Draining it isn't an option either, as it damages the battery to be fully discharged. So, you have to work on the car with a live voltage source present. I'm not sure if most modern EVs have manual disconnect switches on the main power cables where they meet the batteries or if you're just expected to wear rubber gloves and use non-conducting wrenches to unbolt the cables. I'd expect any modern EV will at least have contactors to connect the battery to the motor controller (these are basically electrically actuated switches, like a mechanical relay), which will be disabled when the car is off. In general, though, I'd expect the main power cables to be something that doesn't need maintenance and mechanics can generally steer clear of.