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Comment by misnome | Hacker News Reader

Running out of fuel is something it’s obviously “easy” to do with other cars.

But I’m surprised that the electronics have _no_ power redundancy, there isn’t a manual release for the parking break, and running out of power causes the parking break to fail-closed?

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There seems to be some discrepancy as the article mentions that it ran out of power, but the owner, Mr Grigg, 57, said that the vehicle had failed despite having shown that it had several miles of charge remaining.

And yes, I'm surprised that an important component doesn't have a manual override. Imagine if the vehicle blocked access to a hospital or a busy bridge or tunnel.

Fire Department would just drag it away without thinking twice.

I’m kind of amazed people tolerated this for so many hours. Traffic stoppage costs can really add up.

In New York, sure. In Salisbury? I'm not even sure the fire engines are equipped for that kind of activity, and I'm almost certain the fire service isn't prepared for the liability.

Good point. I really don’t know what the laws would be like there. I just assumed that a fire department would be capable of dragging a sedan and likely immune to liability if they decided it was a public safety issue.

I checked, and they can move vehicles in a situation where failing to act could cause "one or more individuals to die, be seriously injured or become seriously ill."

Just hit it with fire truck out of the way

What liability arises from removing a vehicle blocking a public road for hours?

> But I’m surprised that the electronics have _no_ power redundancy,

They do. All the auxilliary stuff is on a 12V bus just like on any other car, powered by a separate 12V battery. I don't know anything about the parking break per se, but this isn't remotely as simple as "the car can't be towed when the main battery is dead". We know that's not correct; this is hardly the first Tesla to run out its battery, you can find people doing this deliberately on youtube as a test!

It's some other failure that locked the brake. And it's unique enough to be notable, and it's a Tesla, so of course it's going to spend the day on the front page of HN while we all endure the incessant tut-tutting of the hacker class who think the bug is much simpler than it is.

Folks, disabled vehicles block roads all the time. Stuff breaks. Cars are complicated. Why do we not care if it's a Renault or Suzuki?

Teslas have a number of features designed to prevent this situation from happening.

Below a threshold, the car's power will reduce as battery capacity decreases.

The car will also warn you several times with a modal over the entire display telling you that you're approaching zero capacity.

If you're following a route on the navigation system, it will show you a banner just above the turn by turn instructions indicating whether you need to charge or drive below a set average speed in order to reach the destination.

Additionally, there is a small reserve within the battery that allows you to stretch your remaining capacity just a bit.

The issue here (and I blame Tesla more than the driver) is that showing remaining battery capacity in miles is horrifically inaccurate, just like it is with petrol-fueled vehicles.

Percent state of charge is always the most accurate measure to go on, just like it is on phones.

I also wish Tesla would allow drivers to disable percent remaining until a threshold is reached (like 20%) to reduce capacity anxiety.

indeed - I would have thought a separate battery to run the cabin and safety features would be a good idea. I would only have to be 1/100th the size of the motor batteries.

This is the way it works, the high voltage battery is used for the motors and to feed the 12 volt battery which feeds cabin electronics.

I’m guessing by extremely unfortunate luck both batteries failed at the same time.

Safety-wise it's better option.

Breaking vs just rolling without working brakes.

And I really do not like trend of making brakes drive-by-wire instead of mechanical just to (presumably) save few pennies...

The Tesla Model 3 brakes are hydraulic and the pedal is still mechanically connected to the master cylinder. It’s the parking brake which is electronically actuated, as it is with nearly all modern ICE cars.

Isn’t the 12V battery responsible for that? It sounds like the driver lost that somehow, not the main battery.

Is it? What if it runs out of power at 70mph in the middle of a motorway? I’d have thought sudden breaking would have been the most dangerous thing to do

It shouldn't be as emergency stops can be performed at any point in time - usually when there's an emergency. Obviously it's important that following drivers have left enough space so that they can react in time, but that's down to their driving skill (or lack of, if they're too close).

I'd consider that autonomous vehicles should apply the brakes if they find themselves in an uncertain situation as reducing speed is going to minimise any impact. However, this was being driven acoustically and the handbrake shouldn't have been applied automatically by the power running out. At the worst, if a handbrake fails and can't be used, you can always shove a couple of bricks under the wheels to stop the vehicle rolling.

Maximum braking on an empty highway is still quite dangerous.

The problem about “yeah well they should have left space” or “they should have responded perfectly to a car that’s suddenly braking” is that it’s not realistic to the real world. It’s not a least-surprise event.

I'm not sure about the laws there, but in Austria for example it's also illegal to suddenly break without reason.

wonder if the pendulum will shift back to mechanical components being cheaper than the electrical alternatives with the ever increasing demand for electrical components.

There is enough battery to put it into tow mode after you "run out". Assuming he either didn't know how or perhaps you can even run through that in service mode.

Running of electricity is incredibly difficult on an EV. Also, in what way does a parking brake or a transmission prevent towing? You lift the car onto the tow truck bed like any other tow job. It doesn't take nine hours to hire one that can do the job.

They might not have had such flat bed tow trucks. They aren’t super common outside d cities.

yeah its a problem that comes up regularly, fails and can’t be rolled away. probably need legislation because so many ev fanboys pretend this isnt a problem. (i am an ev fanboy)

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