# How does everything else work?



## xnappo (Jun 3, 2017)

I am sure there is a write up somewhere for the S at least, but I am really curious how everything OTHER than the powertrain works on my M3 vs a 'normal' car.

- How do power brakes and power steering get their 'power'
- Is the braking setup standard (master/slave cylinders?)
- How is the AC compressor driven?
- How does the heater work? Is there any generated heat or all from coils?
- What does the 12V battery power?

I know I could find all this from some Googling, but thought it might be fun to discuss...

xnappo


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## Ed Woodrick (May 26, 2018)

I think I'm close, but may be off a little.

- How do power brakes and power steering get their 'power'
12V Battery
- Is the braking setup standard (master/slave cylinders?)
Most of the braking is regen, not sure about the rest
- How is the AC compressor driven?
High voltage (off the main battery) motor
- How does the heater work? Is there any generated heat or all from coils?
Coils and also by battery heat
- What does the 12V battery power?
Pretty much everything you touch. The High voltage is only used for the AC compressor and wheels.

If the 12V battery is dead, the car will not run. Because the computers can't come on.


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## xnappo (Jun 3, 2017)

So I have read on the Model S that the power steering is completely electric and the traditional brakes are hydraulic, with a small motor to create the power-assist.

True for the 3? There is brake fluid, but no power steering - so seems to line up..


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## GDN (Oct 30, 2017)

xnappo said:


> So I have read on the Model S that the power steering is completely electric and the traditional brakes are hydraulic, with a small motor to create the power-assist.
> 
> True for the 3? There is brake fluid, but no power steering - so seems to line up..


I don't know exactly how it works, but steering is "power", just not hydraulic as it was traditionally. On most newer cars it is now magnetic/electric in some way. This is for automatic parking, steering/EAP, etc.


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## Kizzy (Jul 25, 2016)

12-volt battery also engages the contactors for the traction battery (which allows the car to drive or charge).

Heat from the motor(s) is used to heat the battery pack if needed. The AC compressor is also used to cool the battery (in addition to the cabin).


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## garsh (Apr 4, 2016)

GDN said:


> I don't know exactly how it works, but steering is "power", just not hydraulic as it was traditionally.


No, the brakes are definitely hydraulic. It's a traditional brake setup, with split master cylinder. I am not sure how the power assist is applied, but it definitely exists.

Please, let's try to research the correct answers instead of guessing. Otherwise, your grandmother is going to ask if your new car is "the one without brakes that catches on fire and runs over people".


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## GDN (Oct 30, 2017)

garsh said:


> No, the brakes are definitely hydraulic. It's a traditional brake setup, with split master cylinder. I am not sure how the power assist is applied, but it definitely exists.
> 
> Please, let's try to research the correct answers instead of guessing. Otherwise, your grandmother is going to ask if your new car is "the one without brakes that catches on fire and runs over people".


There was no guessing. You have to keep the replies in context. I didn't mention brakes - specifically mentioned steering and I can promise you it is not hydraulic. It isn't on most any new car driven. The model 3 talks about brake fluid and windshield washer fluid, they are the only two mentioned.


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## garsh (Apr 4, 2016)

Mea culpa. I read too quickly.

<shame cube>


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## CoastalCruiser (Sep 29, 2017)

Have you viewed the Ingineerix teardown video? Not a complete answer, but he does point out and discuss several of the subsystems.


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## JWardell (May 9, 2016)

-Cabin heating is high voltage resistive PTC heater (like resistors but safer)
-Battery heating is by running current through the traction motor without spinning, as they share a coolant loop
-Steering is electric steering, same as used by most other premium brands in the last 5+ years, probably 12v
-AC is electric motor compressor. Like the ones in your house. Not sure if 12v or 400v.
-I don't know about brakes, probably also a 12v hydraulic pump
-The 12v system powers all the usual electronics system. Instead of fuses, the Model 3 uses "solid state fuses" or simply electronic switches with a current sense for each circuit. It can detect very precise current differences and disable circuits instantly, and re-enable them when things are good again.

I hope to know much more electric details once there is one in my driveway


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## Diamond.g (Jun 26, 2017)

In the S Bosche iBoosters were used. I think the 3 is the same or st least similar.


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