# Adjustment of Variable Resistance in an automobile battery

In summary: Great minds think alike, fools never differ.Great, thank you to Steve4Physics and Baluncore for the answers. One more question, the alternator and the battery are to be treated as two separate sources of emf or a single whole system of emf source?The alternator and the battery are to be treated as a single unit - a 'black box' which always supplies 12V; you don't care how the 12V got there!

TL;DR Summary
Adjustment of Variable Resistance in an automobile battery
How is the load (variable resistance) adjusted in an automobile battery? Mechanically (potentiometer, rheostat) or electronically

(digital potentiometer) or are both configurations possible.Can the load in a automobile battery be a three terminal divider (potentiometer) or is it almost always a rheostat?

Besides adjusting audio volume, what else is a potentiometer useful for specially in an automobile?

Please let me know if I should start a new thread for this. I included the questions here because of their relevance to the topics discussed in this thread.

Thanks,

Batteries don't have have a variable resistance in them. In normal operation, a battery simply provides a constant voltage (ignoring the effects of internal resistance).

The battery delivers current according to whatever the total load happens to be. E.g. if you turn the lights on, the battery delivers more current.

Maybe you are confusing this with a simple laboratory setup, where a battery and potentiometer or rheostat are used to perform experiments. That's not what happens in a automobile circuit.

Can the load in a automobile battery be a three terminal divider (potentiometer) or is it almost always a rheostat?
The 'load' just means whatever is connected to the battery, e.g. lights, starter motor, radio, wiper motor. It is never a rheostat,

Also, potentiometers and rheostats would be very wasteful because of the amount of heat they produce with large currents.

Besides adjusting audio volume, what else is a potentiometer useful for specially in an automobile?
Have you tried typing "automobile potentiometers" into a search engine? What did you find?

Edit - typo's corrected

russ_watters
An automobile battery does NOT have an adjustable variable resistance.
The battery voltage remains reasonably fixed, usually near 12 volts.
The load current drawn from the battery by electrical accessories is determined by the individual accessories.
The battery is charged by an alternator. The voltage and charging current are regulated by changing the alternator field current.

russ_watters
Baluncore said:
An automobile battery does NOT have an adjustable variable resistance.
The battery voltage remains reasonably fixed, usually near 12 volts.
The load current drawn from the battery by electrical accessories is determined by the individual accessories.
The battery is charged by an alternator. The voltage and charging current are regulated by changing the alternator field current.
Great minds think simultaneously!

russ_watters and berkeman
Steve4Physics said:
Great minds think simultaneously!
Great minds think alike, fools never differ.

russ_watters and Steve4Physics
Great, thank you to Steve4Physics and Baluncore for the answers. One more question, the alternator and the battery are to be treated as two separate sources of emf or a single whole system of emf source?

While the engine is running, the alternator supplies all the accessories, and charges the battery.
When the engine is not running, the battery must supply the accessories.
The battery terminals are common to all circuits.

jack action
... the alternator and the battery are to be treated as two separate sources of emf or a single whole system of emf source?
That depends on what you are trying to do. For example:

If you are designing a car’s charging-circuit, you would need to treat the battery and alternator as 2 separate sources of emf.

But if you are designing the car’s audio system, you would effectively treat the battery and alternator as a single unit – a ‘black box’ which always supplies 12V; you don't care how the 12V got there!

Also,did you find uses for potentiometers by doing a search?

TL;DR Summary: Adjustment of Variable Resistance in an automobile battery

How is the load (variable resistance) adjusted in an automobile battery? Mechanically (potentiometer, rheostat) or electronically

(digital potentiometer) or are both configurations possible.Can the load in a automobile battery be a three terminal divider (potentiometer) or is it almost always a rheostat?

Besides adjusting audio volume, what else is a potentiometer useful for specially in an automobile?

Please let me know if I should start a new thread for this. I included the questions here because of their relevance to the topics discussed in this thread.

Thanks,
If you are referring to the internal resistance. of a battery....
The internal resistance acts like a Thermistor....The resistance changes quickly with heat ..

## 1. How does adjusting the variable resistance affect the performance of an automobile battery?

Adjusting the variable resistance in an automobile battery can affect its performance in several ways. By increasing the resistance, the battery's output voltage will decrease, resulting in a slower and weaker start for the car. On the other hand, decreasing the resistance can lead to a higher output voltage, which can cause damage to the car's electrical components.

## 2. What is the purpose of the variable resistance in an automobile battery?

The variable resistance, also known as the load or external resistance, is used to regulate the flow of electricity in the battery. It helps to control the output voltage and current, ensuring that the battery does not overcharge or undercharge the car's electrical system.

## 3. How do I know when to adjust the variable resistance in my car battery?

There are a few signs that indicate the need to adjust the variable resistance in your car battery. These include difficulty starting the car, dimming headlights, and a low battery warning light on the dashboard. If you notice any of these symptoms, it may be time to adjust the variable resistance to optimize the battery's performance.

## 4. Can I adjust the variable resistance myself, or do I need a professional?

Adjusting the variable resistance in an automobile battery is a relatively simple process that can be done by anyone with basic knowledge of car maintenance. However, if you are unsure or uncomfortable doing it yourself, it is always best to consult a professional to ensure it is done correctly.

## 5. What are the potential risks of adjusting the variable resistance in a car battery?

Adjusting the variable resistance in a car battery can be risky if not done correctly. If the resistance is set too high, it can cause the battery to overcharge, leading to damage to the car's electrical components. If set too low, it can result in undercharging, which can cause the battery to die prematurely. It is essential to follow the manufacturer's guidelines and consult a professional if unsure.

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