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Your computer power supply has a ~400 volt rail in it. Are you unwilling to ever open a desktop computer? The Tesla battery has contactors inside of it, so you

Your computer power supply has a ~400 volt rail in it. Are you unwilling to ever open a desktop computer? The Tesla battery has contactors inside of it, so you'll only have 400V live when the car is on. Additionally, assuming the HV is floating relative to the chassis, you need to touch two spots at different potentials to actually get shocked. That said, it looks like this is an attempt to prevent service of a lot of non-powertrain components, considering that the Tesla owner in the article got a letter for connecting just to the ethernet port.

rsync 11y ago
"Your computer power supply has a ~400 volt rail in it. Are you unwilling to ever open a desktop computer?" Not at 1000 amps, it doesn't ...
- TD-Linux 11y ago
  Right, but how many amps are flowing through a wire isn't going to change how badly it electrocutes you.
  - vl 11y ago
    Actually, it's other way around - amps matter a great deal. 400 volts with low amps feels like a sting. I've touched 25K volt contact once (by mistake), while unpleasant (and some damaged skin), managed just fine - cause very low amps.
    - TD-Linux 11y ago
      I think what you're after is that the impedance matters a great deal - a high voltage but high impedance source will drop in voltage a lot and not deliver a large current into the body. In both examples I gave, the PSU DC bus and the car, both are much lower impedance than the human body and the difference is likely negligible.
saulrh 11y ago
> Your computer power supply has a ~400 volt rail in it. Are you unwilling to ever open a desktop computer? If it's plugged in and turned on - yeah, sure, I don't want to muck around in there. The thing is, my computer power supply: * Can be completely physically disconnected from the rest of the computer * Doesn't have a battery in it If I pull the plug on my desktop, disconnect the power supply, and maybe if I'm being really paranoid touch a lamp to it just to be sure there isn't anything trapped in a cap or inductor, I know that that 400 volt rail is actually at zero volts relative to anything near me. Batteries? Especially power batteries that I can't guarantee are physically disconnected, and that can't really be grounded because they're inside an insulated mobile platform? It's more like looking inside a microwave oven or a CRT, and you're damn right that I don't open those up.
- smileysteve 11y ago
  > Doesn't have a battery in it Any work done on a car w/ airbags (the last 20 years) has had a risk of airbag explosion with any localized short. The Takata airbag recall means that many of these may shoot shrapnel at you. And the original airbags were known for occasionally flinging phosphorous at you. Beyond that, Lead Acid batteries can be dangerous when the battery or the alternator fails - that's not steam, that's sulphuric acid steam.
  - saulrh 11y ago
    I don't know why airbags aren't opto-isolated digital devices activated by simple challenge and response over canbus (read a single byte off address 0, write the same byte back to address 1 to trigger). I'd have expected pyrotechnics to have been first on the list for conversion to digital.

rsync 11y ago

"Your computer power supply has a ~400 volt rail in it. Are you unwilling to ever open a desktop computer?" Not at 1000 amps, it doesn't ...

TD-Linux 11y ago
Right, but how many amps are flowing through a wire isn't going to change how badly it electrocutes you.
- vl 11y ago
  Actually, it's other way around - amps matter a great deal. 400 volts with low amps feels like a sting. I've touched 25K volt contact once (by mistake), while unpleasant (and some damaged skin), managed just fine - cause very low amps.
  - TD-Linux 11y ago
    I think what you're after is that the impedance matters a great deal - a high voltage but high impedance source will drop in voltage a lot and not deliver a large current into the body. In both examples I gave, the PSU DC bus and the car, both are much lower impedance than the human body and the difference is likely negligible.

saulrh 11y ago

> Your computer power supply has a ~400 volt rail in it. Are you unwilling to ever open a desktop computer? If it's plugged in and turned on - yeah, sure, I don't want to muck around in there. The thing is, my computer power supply: * Can be completely physically disconnected from the rest of the computer * Doesn't have a battery in it If I pull the plug on my desktop, disconnect the power supply, and maybe if I'm being really paranoid touch a lamp to it just to be sure there isn't anything trapped in a cap or inductor, I know that that 400 volt rail is actually at zero volts relative to anything near me. Batteries? Especially power batteries that I can't guarantee are physically disconnected, and that can't really be grounded because they're inside an insulated mobile platform? It's more like looking inside a microwave oven or a CRT, and you're damn right that I don't open those up.

smileysteve 11y ago
> Doesn't have a battery in it Any work done on a car w/ airbags (the last 20 years) has had a risk of airbag explosion with any localized short. The Takata airbag recall means that many of these may shoot shrapnel at you. And the original airbags were known for occasionally flinging phosphorous at you. Beyond that, Lead Acid batteries can be dangerous when the battery or the alternator fails - that's not steam, that's sulphuric acid steam.
- saulrh 11y ago
  I don't know why airbags aren't opto-isolated digital devices activated by simple challenge and response over canbus (read a single byte off address 0, write the same byte back to address 1 to trigger). I'd have expected pyrotechnics to have been first on the list for conversion to digital.