I"ve heard a story the a weak auto battery can ruin an alternator or reason an alternator to fail early.

Is this true, or is it mostly fiction?




You are watching: Can a bad battery ruin an alternator

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Your question is an overwhelming to answer there is no you learning the inner operations of one alternator.

The basics. If you move a magnetic field near a coil of cable the electrons in the wire get excited and electricity will certainly be made. The amount of electrical power made depends on the size of the magnetic field and its speed. The enlarge the field and also the much faster it"s moving the much more electricity is made. Likewise if you have actually a coil that wire and you happen a existing through that it will develop a magnetic field.

An alternator has actually 4 basic components; rotor, stator, voltage regulator and bridge rectifier.

The rotor is the component that spins. On the rotor there is a coil of wire. By sending a current down that wire a magnetic field is created. Then by spinning the rotor a moving magnetic field is created. Due to the fact that the rotor is spinning, gadgets known as slip ring are needed to send uninterrupted existing to the rotor. The slip rings room solid brass or copper ring that have stationary spring-loaded carbon brushes riding ~ above them. The voltage regulator controls the mechanism voltage. The voltage regulator sends current to the rotor with the carbon brushes and slip rings. They work-related in tandem. If the system voltage is short the voltage regulator will send much more current come the rotor. If the mechanism voltage is as well high the voltage regulator will send less present to the rotor. The stator is the stationary coil that wire that is excited through the spinning magnetic field of the rotor. In fact there room 3 separate coils of cable in the stator be separate by 120 degrees. The calculation of the stator is alternative current (AC).The leg rectifier then converts the AC into direct current (DC) that the car can use.

The entirety system is draft to carry out two things. First, refill the battery after the cranks the engine. Second, supply strength to the rest of the car. The method the totality thing works together is the the voltage regulator senses the voltage that the device and change the rotor current accordingly. When for instance the head lights room flipped ~ above this gift a higher load and lowers the system voltage. The voltage regulator senses this and change the rotor present accordingly. Then you go to happen someone on the highway and mash down the gas pedal. This accelerates the engine and also the device voltage will go up. The voltage regulator lowers the rotor present to carry the mechanism voltage down. This cat-and-mouse game constantly go on in the charging system.

When an alternator is rated because that a specific current output, lets say 100 amps, that rating is in ~ 2000 RPM. The alternator have the right to comfortably make 100A in ~ 2000 RPM. That is draft that way because usual cruise is approximately 2000 RPM. In ~ idle, the rotor is spinning slower and also the alternator is i can not qualify of making it"s full rated current. At idle, is when a charging system can obtain into trouble.

A battery is a pig. A battery will certainly take all the existing it wants and also no less. The present it desire is proportional come its state of charge. A discharged or weak battery is really hungry because that current.

To bring it all together, when a auto has a weak battery the battery will certainly want lots of current. The present demand of the battery lowers the device voltage for this reason the voltage regulator compensates through sending more current with the rotor. At idle, the alternator is i can not qualify of making the required current. Because of this the system voltage autumn even an ext and the voltage regulator sends out the maximum present through the rotor.

This maximum-load, minimum-speed condition is wherein the wear happens. At the minimum rate the minimum lot of cooling is available from the integrated fan. At the maximum pack the voltage regulator will press the maximum quantity of existing through the rotor and through the brushes and slip rings. The brushes and slip rings gain hot and with no extr cooling easily accessible from the pan they will wear faster.

If the RPM is raised to over 2000 the instance gets much better because an ext cooling is obtainable and the existing through the rotor decreases. This will certainly unfortunately move the wear point from the pen to the leg rectifier since now it has to rectify the preferably current.

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This is preferable, however, together the leg rectifier is a solid state component and is much much less subject come wear.