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Comment by jauntywundrkind | Hacker News Reader

Extra low voltage is 50v ac or 100v dv. https://en.wikipedia.org/wiki/Extra-low_voltage

For some reason people assume it's 48v DC or 50v dc. But it's double that. That said, I feel significantly more scared dealing with 100v DC than I do 48 or 24v.

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I find 48V a lot less scary when cars are involved than 12V. Neither is particularly likely to electrocute me, but 48V comes with fuses that will trip at 1/4 the current, giving 1/16 the resistive heating if something shorts, which is a lot less likely to melt or ignite things. Also, the wires are much smaller :)

> 1/4 the current, 1/16 the resistive heating

Really underappreciated safety aspect. The currents required for your average doodad at 48V leave you with a MUCH lower chance of unscheduled welding.

Remember folks, everything is a fuse if you put enough current through it, as a rule of thumb it's good to keep "enough" pretty low.

"The job of the transistors is to protect the delicate fuses."

--old EE lore

ELV is not a fundamental definition of "safe". The limits of what's safe depends on the application and your risk tolerance, and ELV is just a name for a couple of definitions out of many.

Also, those numbers are for ripple-free DC, which you're not going to find in a car. They're cut roughly in half for ripple peaks.

I have been shocked by 110V DC and let me tell you, it hurts. A lot. Would not recommend.

That's for IEC. Under OSHA it's 50 volts, AC or DC.

I used to work on vacuum tube power amps. 400v+ B+ with big caps is stressful to deal with. And doing it a lot can lead to complacency.

We used to call getting shocked "getting a taste" - like getting a taste of ice cream, except it's more like a microsecond blackout.

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