Capacitors in Cars: What Parts & Types?

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Discussion Overview

The discussion centers on the use of capacitors in automobiles, exploring which parts require capacitors and the types of capacitors utilized in these applications. The scope includes technical explanations and practical applications within automotive systems.

Discussion Character

  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant inquires about the specific parts of an automobile that utilize capacitors and the types of capacitors used, such as aluminum, tantalum, and ceramic.
  • Another participant shares a historical perspective on the need to disconnect the battery before working on the steering wheel, suggesting that capacitors may play a role in airbag systems.
  • A participant notes that capacitors are commonly used for ignition noise suppression, particularly in older cars where they can be found in the distributor, and mentions their presence in modern Engine Management Computer systems.
  • It is mentioned that a capacitor across the ignition system's points helps generate a sufficiently long spark.
  • A participant discusses the use of large capacitors in hybrid cars, particularly in the inverter module, describing them as significantly larger than typical capacitors.
  • Another participant explains that capacitors are used to smooth out the ripple in the DC output from the alternator, which is initially AC and converted through diodes.

Areas of Agreement / Disagreement

Participants present various applications and types of capacitors in automobiles, but there is no consensus on specific types used in all cases or the exact roles of capacitors in different systems.

Contextual Notes

Some claims about capacitor types and their functions are based on personal experience or historical context, which may not encompass all modern practices or variations across different vehicle models.

wzheng1837
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Hi!

Does anyone know which parts of an automobile would require the use of capacitors?

Also, what kinds of capacitors are used in this case? (aluminum, tantalum, ceramic, ??)

Many thanks!
 
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In locksmith college, back in '79, we were taught that we have to disconnect the battery at least 11 minutes before pulling the steering wheel in order to let the airbag trigger "bleed down". I assume that caps are involved in that. No idea what kind.
 
Capacitors are often used in cars for ignition noise suppresion.
on older cars you will find one in the distributor.
Capacitor Discharge Ignition units with have a couple
in more modern cars you will find lots of capacitors in the Engine Management Computer systems.

The suppression ones will generally be non electrolytic ~ 1 uF give or take a bit
CDI's and EMC's will likely to have a mix of types

Dave
 
A capacitor is placed across the 'points' in the ignition system to enable a spark of sufficient duration to be generated
 
Hybrid cars use relatively large capacitors in the inverter module. I don't know what kind they are but compared to other capacitors I've seen they're freakin' huge. The size of soda bottles.
 
The alternator is a belt-driven AC generator. That AC is fed to diodes that convert it to DC. The DC that comes out of a rectifier is very wiggley. A parallel capacitor eliminates a lot of the ripple on that DC level, by making use of the old rule that the voltage across a capacitor can't change any faster than charges can be physically moved onto or off of its plates (Q=CV).
 

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