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Comment by tragictrash | Hacker News Reader

Personally I would have liked to see the reasoning presented in that safety message. Something like "high voltage is present under the hood" or "only qualified personnel have the tools to safely open the hood".

Same applies for your no trespassing example. I would like to see "no trespassing, danger high voltage"

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This.

Plenty of people think they're "smart" - and assume they know better than a vague warning sign: When some people see a "Danger confined space" sign they're going to think the danger is banging your head on the low-ceiling; that's not the real danger of confined spaces: a bigger threat is unbreathable gasses, like CO2, that tend to pool at the bottom of confined spaces: that's often the real danger. But yet I've never seen a sign saying "Danger: confined space: CO2 pooling risk" or similar.

This. But the problem aren't the people, but the vague warning sign. Another example is

The problem is that many warning signs don't exist to warn people, but to prevent lawsuits. So they are phrased as generally as possible and often include false positives.

There’s no warning sign for CO2 risk that will work for a non-expert. You have to go for the basics (“risk of suffocation and death”) at that point, because no one knows that you can drown in CO2.

These ones would work for me:

"CO2 pooling risk" "Gas pooling risk" "Risk of suffocation"

“There’s no visible pool of water, must be fine”

I disagree. I think that most of the population of United States would understand that oxygen deprivation is bad. I agree that coming up with verbiage for a sign that clearly communicates the correct intent would be difficult.

Isn't that kindof what the list of warnings below the message provides? I think you can click on them to expand them, and based on what's in the owner's manual I expect one of the warnings is about "components under voltage".

I don't think there are really any major risks to human life from the high voltage under the hood of an EV.

The electrical system checks for earth leakage faults all the time, and will switch off if it finds one. That means a baby can chew any of the big scary orange wires and still survive.

The only real dangerous bit of an EV is the battery pack - if you cut it open.

In your case it appears that Mercedes made the right decision. 400 V DC with for all practical purposes an internal resistance so low that it might as well be zero is about as nasty as it gets. Zero warning until you touch that live terminal and then no way to disconnect if you happened to grip it the wrong way, and when you short it out you're going to be in for a world of hurt.

The earth leakage protection only applies to the charging circuitry primary.

So, even if I don't agree with the principle it looks like for some users this actually applies, which I find somewhat surprising.

The earth leakage protection applies to the whole system.

> no way to disconnect if you happened to grip it the wrong way

This is what the explosive breakers are for.

Here is an article with more details:

https://www.vehicleservicepros.com/service-repair/battery-an...

Note that it appears there are a few hybrid cars made in the 90's without this protection!

This is only about chassis ground current, not earth leakage, which is strictly the domain of the charging circuitry.

Seriously: if you do not understand the difference please do no not start messing with the HV side of an electric vehicle. Below 48 V is considered a safe voltage but can already - under the right conditions - cause you plenty of hardship and I'm aware of one death from a 48 V system.

Anything higher than that with voltages between 200 and 600V pretty much the nastiest range because it is too low to arc and high enough to kill you needs special precautions, tools and ways of working to keep you safe.

You can't rely on technical measures to keep you safe when diagnosing and repairing those circuits because those technical measures could be the cause of the fault.

The explosive Breakers would not help you in this case. Those Breakers likely blow in hundreds of amps range, you only need one 100th of an amp to stop your heart.

Don't worry buddy we'll do everything we can to get those enhanced warning messages out there so you can be safe too.

Definitely agree. My first thought was "but yes", after reading the article I am not so curious to peek under. Perhaps the marketing department doesn't like the idea of the car being "danger"-ous.

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