Welcome Guest. Sign in or Signup

2 Answers

C-172 Electrical system

Asked by: 7233 views Aircraft Systems

What keeps the electrical system from overcharging the battery?  I thought the voltage regulator provided this protection but during a recent discussion with an assigned CFI at my flight school, there was doubt raised.  What is the answer?

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

2 Answers



  1. Wesley Beard on Dec 27, 2010

    It is the combination of the alternator and the regulator that keeps the battery from overcharging.  The alternator voltage is regulated by the voltage regulator.  The amperage is controlled by the output of the alternator and the regulated voltage.
     
    When the battery is charged it is said to have a certain amount of electromotive force (EMF).  This force pushes back against the electromotive force of the alternator current.  When the battery needs charging, the battery EMF cannot withstand the EMF of the alternator and thus the battery accepts the current and charges itself.  When the forces are equal, charging stops.
     
    With this method, it is impossible, without a failure of the alternator, to overcharge the battery.  It’s a pretty slick method.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  2. Jim Foley on Dec 27, 2010

    In addition to Wesley’s post, As you know, the batteries in small aircraft are generally 12 or 24 volt systems.  The alternators are generally a few volts higher, such as 14 and 26.  The volatege needs to be higher to counter act the EMF mentioned above, but is not a large enough difference to couse damage, unless it malfunctions.  Due to the physical properties of the alternators, such malfunctions are virtually impossible.

    0 Votes Thumb up 0 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.