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Comment by serf | Hacker News Reader

you're correct. a '12v ICE' alternator generates up to 14.8-15.2v. Most automotive stuff can operate between 9ish-16ish-v , of course totally depending on the product.

of course this is just a modern interpretation. older stuff runs at 6v and some weirdo offbeat cars have a 24v/48v rail sitting around somewhere. Cop cars often had alternators that put out weird voltage ranges for certain equipment, or dual 12v for high amperage output.

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Even just a "12v" automotive battery itself is mostly dead if if actually reads 12.0V. Fully charged is around 12.6 or 12.7. If a car had an electrical system that actually ran at 12 volts, the battery would always be dead.

"12v" in reference to anything automotive is very much a nominal reference.

Whilst cranking, an ICE car will drop to around 6 volts (then maximum power is extracted according to thevenim's theorem).

That means all computers etc will work at 6v.

> Whilst cranking, an ICE car will drop to around 6 volts (then maximum power is extracted according to thevenim's theorem).

> That means all computers etc will work at 6v.

Not necessarily all of them. Plenty of stuff will drop out while cranking; hopefully not the computers that run the fuel injection and ignition, though.

Interesting. I now know why my windshield wipers quit for a sec when my vw auto stop/start kicks back on.

Not a car engineer, but those motors can be pretty high A, so this could also just be a feature that helps the starter get as much power as it can while cranking.

Ignition switches were turning off the wipers and other such extras in the 1980s. Probably longer but I'm not old enough to remember

Some accessories are disconnected while cranking so the battery can supply as much current as possible to the starter.

The specs say no less than 6volts. In the real world when the temperature drops down to -70F or colder and batteries get old the voltage goes well below that: deal with it.

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