how much resistance should a car battery have

Full Answer

What is the internal resistance of a car battery?

For your car battery to have optimum performance there should be a low resistance. Voltage is calculated by adding external resistance to internal resistance. The primary responsibility of internal resistance is to determine the runtime of a battery. The most urgent requirement of a car battery is for it to have low internal resistance.

How to calculate the voltage of a car battery?

Voltage is calculated by adding external resistance to internal resistance. The primary responsibility of internal resistance is to determine the runtime of a battery. The most urgent requirement of a car battery is for it to have low internal resistance.

What is the most urgent requirement of a car battery?

The most urgent requirement of a car battery is for it to have low internal resistance. If your battery internal resistance reads with high ohms, it means that your battery is low and might need a recharge. A car has energy requirements for it to run efficiently thus the internal resistance should be low.

How do you determine the internal resistance of a 12V battery?

How do you determine the internal resistance of a 12 v car battery? For your car battery to have optimum performance there should be a low resistance. Voltage is calculated by adding external resistance to internal resistance. The primary responsibility of internal resistance is to determine the runtime of a battery.

What is a good battery resistance?

Ideally, a battery should have 0Ω internal resistance. So during battery operation, all the voltage will be dropped across the element that the battery is powering instead of the battery dropping voltage across itself. According to voltage division, voltage drops across the element with the higher impedance.

What is the resistance of 12V?

The resistance “seen” by the 12-Volt battery is 500 ohms .

How many ohms should a car battery read?

The internal resistance of a 12-volts car battery is about 0.02 ohms.

What does high resistance in a car battery mean?

High resistance causes the battery to heat up and the voltage to drop under load, triggering an early shutdown. Figure 1 illustrates a battery with low internal resistance in the form of a free-flowing tap against a battery with elevated resistance in which the tap is restricted.

How do you check car battery resistance with a multimeter?

1:076:09How to Test a Car Battery with a Multimeter - YouTubeYouTubeStart of suggested clipEnd of suggested clipOn for about two minutes this will get rid of any surface charge the battery may have as we waitMoreOn for about two minutes this will get rid of any surface charge the battery may have as we wait what you want to do is you want to turn on your volt meter.

How do you check battery resistance with a multimeter?

2:497:47How to measure internal resistance of battery with digital multimeterYouTubeStart of suggested clipEnd of suggested clipWe have to measure the value of the resistor. And VL is the load voltage that will we will measureMoreWe have to measure the value of the resistor. And VL is the load voltage that will we will measure across the load resistance which is RL. So how we can get the internal resistance of the battery.

How do I know if my car battery is weak?

Watch for these five telltale signs of a bad battery so you aren't caught out in the cold!...5 Unmistakable Signs Your Car Battery is FailingDim headlights. ... Clicking sound when you turn the key. ... Slow crank. ... Needing to press on the gas pedal to start. ... Backfiring.

How do you know when car battery needs replacing?

6 Signs Your Car Battery Needs to Be ReplacedThe Engine Is Slow to Turn Over. ... The Dashboard Lights Flicker. ... The Windows Roll Slowly. ... The Headlights Go Dim When Idling. ... Corrosion is Present. ... Your Battery is Old. ... Conclusion.

How can you tell when your car battery is going bad?

Bad Battery Symptoms If the cranking of the engine is sluggish, like your vehicle is harder to start on cold mornings, it starts inconsistently, or there's no sound and interior lights when you try to start, suspect a failing battery, a loose or corroded connection or electrical draw.

What is too much resistance?

A high-resistance connection (HRC) is a hazard that results from loose or poor connections in traditional electrical accessories and switchgear which can cause heat to develop, capable of starting a fire. Glowing connections occur when relatively high current exists in a relatively large resistance object.

At what percentage should I replace my car battery?

Generally speaking, however, a car battery should be replaced when it reaches about 50% of its full capacity. This can vary depending on the make and model of the battery, so it's always best to consult your owner's manual or a reliable automotive technician for specific advice.

What is the internal resistance of a dead battery?

It gives a "Internal Resistance" of 100 milliohms for a charged battery and an "Impedance" of 35 milliohms for the same charged battery.

What resistor do I need for LED 12V?

Resistor = (Battery Voltage – LED voltage) / desired LED current. So assuming a 12-volt power source and a white LED with the desired current of 10 mA; The formula becomes Resistor = (12-3.4)/. 010 which is 860 ohms. Since this is not a standard value I would use an 820-ohm resistor.

How do you test a 12-volt resistor?

0:031:01Ballast Resistor - How to Test - YouTubeYouTubeStart of suggested clipEnd of suggested clipTake one lead from your voltmeter connect it to the side coming from the ignition switch. Take theMoreTake one lead from your voltmeter connect it to the side coming from the ignition switch. Take the other week when we voltmeter connect it to ground. Now reach in the car. And turn the key to the on.

How do I calculate resistance?

If you know the total current and the voltage across the whole circuit, you can find the total resistance using Ohm's Law: R = V / I. For example, a parallel circuit has a voltage of 9 volts and total current of 3 amps. The total resistance RT = 9 volts / 3 amps = 3 Ω.

How do you reduce a 12V to 5v with a resistor?

Connect 12 v to pin 1 ,pin 2 is the ground and pin3 gives 5v. Don't want to use IC or not getting it,use a voltage divider using 2 resistors and you are done with it. Connect 12 v across the series combination of 4.7k ohm and 6.8k ohm(readily available standard ) resistor and take the output across 4.7k ohm.

Homework Statement

An automobile battery has a terminal voltage of 12.8 V with no load. When the starting motor (which draws 90A) is running, the terminal voltage drops to 11.0 V. What is the internal resistance of the battery?

The Attempt at a Solution

I think I'm just completely over thinking the problem and maybe missing something. In order to find EMF:

Answers and Replies

Hi Reliquo, Welcome to Physics Forums! Your result looks okay. The no-load terminal voltage of the battery will be its EMF. The drop in terminal voltage due to a given current draw will be the drop across its internal resistance, so ΔV/I is the correct way to proceed, as you did.

What is the resistance of a battery?

Ideally, a battery should have 0Ω internal resistance. So during battery operation, all the voltage will be dropped across the element that the battery is powering instead of the battery dropping voltage across itself. According to voltage division, voltage drops across the element with the higher impedance. Ohm's law tells you this in V=IR, showing the higher the resistance, the greater the voltage drop. So if a battery has 0Ω of resistance and it will power a device that has at least some impedance, this ensures, according to ohm's law, that the device will get the voltage and not the battery. This is the ideal case but it doesn't occur in real life.

What is the internal resistance of an AA battery?

Internal resistance also increases as the battery discharges. Therefore, a typical alkaline AA battery may start out with an internal resistance of 0.15Ω but may increase to 0.75Ω when 90 percent discharged.

How much resistance does an alkaline battery have?

Batteries will always have some resistance. Though the internal resistance may be or appear low, around 0.1Ω for an AA alkaline battery, and about 1Ω to 2Ω for a 9-volt alkaline battery, it can cause a noticeable drop in output voltage if a low-resistance load is attached to it.

How does voltage work?

This is understood when you take into account how voltage division works. Taking into account ohm's law, voltage is equal to current * resistance (v=ir). The larger the resistance is, the more voltage gets allocated to that component. If a component has a very large impedance, that component will get most of the voltage, which comes from the battery. However, if the component has a small impedance, say, a few ohms, the voltage output from the battery will not necessarily be received fully by the component. Voltage may be lost, because the battery's internal resistance may compete with that element and the battery will drop voltage across itself instead of the component. This is for small load impedances. Remember, voltage gets allocated according to impedance values. So the impedance of the output device and the battery will always be divided up between each other.

Why is voltage lost in a battery?

Voltage may be lost, because the battery's internal resistance may compete with that element and the battery will drop voltage across itself instead of the component.

How to measure open circuit voltage?

Without any load, we can meaure the open-circuit voltage of the battery by placing a multimeter on the DC voltage setting to measure voltage. This voltage is essentially equal to the battery's rated nominal voltage- the voltmeter has such high input impedance that all of the voltage drops across it. Therefore, it's able to measure the voltage fully. Another way to consider it is that is has such high input impedance that it draws practically no current (v=ir), so there is no appreciable voltage drop.

What is the purpose of the internal resistance table?

This table is useful when selecting batteries. The lower the internal resistance, the more desirable the battery. The lower the internal resistance, the more current it can output. However, the batteries all have their different uses, and if high current output is not a necessity, other battery selections can be just as useful.

Car Battery Voltage: What You Need to Know

While most people know that car batteries are 12-volt DC batteries, there’s a lot more to the story than that, and a car battery voltage range test may be just what you need to find out all the necessary details about your battery’s overall condition.

The Basics of Taking a Voltage Reading

Knowing your battery’s voltage range is a good starting point, but it isn't enough. A healthy battery might have low voltage if it's discharged--it's not an indicator of the battery's internal health.

What Is a healthy Car battery voltage?

Measuring your car battery’s voltage can be a great way to determine how charged your battery might be. The ideal car battery voltage with the engine running is between 13.7 and 14.7V. With the engine off, you should get a reading of 12.6 volts.

Car Battery Load Tests

Measuring voltage tells you about the charge of the battery, but is not an accurate indicator of the health of the battery. In other words, a battery might have a low charge (and therefore a low voltage) but still be a healthy battery. Performing a load test is a reliable check of the battery's internal health.

Do You Have to Replace Your Battery?

So let’s say your battery measures less than 12V on a regular basis, and it failed the load test. Should you replace it? This isn’t a decision you can take lightly, especially if your car requires a more expensive battery. You can first start by using a charger or jump starting your vehicle.

How to find battery rating on car?

At the top you’ll be able to see where your car battery rating would fit in. Simply look at the sticker on your car battery and find where you’d be by using CCA (cold cranking amps), RC (reserve capacity), or the equivalent amp hours based on my extrapolations from a battery charger manufacturer’s data that I did from a previous article which you can check out here if you’d like to see how I got those calculations.

How to keep car battery in peak shape?

If you plan on disconnecting your car battery for any reason such as to go on vacation, or maybe you just don’t use a certain vehicle throughout the winter, the best a way to keep your battery 100% peak shape is to hook up a smart charger that has a float mode that will keep your battery in optimum health while not in use.

What happens when a battery is not connected to a float charger?

What this means is that the chemical reaction inside of the battery reverses itself from a full charge to a state of discharge slowly over time as the result of not being connected to a float charger which keeps the battery topped off at 100%.

How many amps does a car draw?

On newer cars the parasitic draw is slightly higher than on older cars due to the increase of electronic systems. A normal parasitic draw is about 50mA or 0.05 amps, but the range can be anywhere from about 0.03 to 0.085 amps (30-85mA).

How long does it take for a car battery to drain?

A typical car battery will drain in 2-3 weeks and be unable to start your car due to the parasitic draw from the car’s electronics. With the negative terminal disconnected, a healthy car battery will only self-discharge at 5% per month. Let’s get into the details!

Why does my car battery drain when I drive it?

The primary reason why your car battery drains when it’s connected to your car (even though you haven’t driven it) is due to the fact that all of the electronics on the car are connected back to the battery and they never truly turn off. Your satellite radio, GPS system, anti-theft system, and radio presets all slowly drain your battery even ...

How much does a lead acid battery lose?

Luckily, lead-acid batteries have a fairly slow self-discharge rate and you’ll lose about 4-5% of your overall charge on a monthly basis.

What is the resistance of a battery cable?

A battery cable should be 0 ohms resistance from one end to the other. Or very close to it.

Why is there always a draw on the battery in a car?

Because of the electronics on a car there is ALWAYS a draw on the battery due to keeping memories alive which cannot be turned off. Ohm measurement like you are talking about is never taken cause we just fix the darn things we aren't engineers.

Is 4 ohms a short to ground?

Thanks anyway. Clearly, it should be a lot greater than 4 ohms. Four ohms is like a short to ground. (There is such a thing as a short to voltage, but this is NOT that.) Imagine a battery seeing 4 ohms when the key is ON.

Why do you need resistance in an electric circuit?

You need the resistance of the load of an electric circuit in order for the circuit to function , but if you have unwanted resistance, the circuit will not function as intended .

What is resistance check?

Resistance checks are done on open circuits that are isolated from the rest of the circuit. When doing resistance checks, you must remove what you’re checking from the circuit first in order to do your resistance check; otherwise, you might damage the circuit or your meter.

What is the R in a circuit?

Resistance (R) in the Ohm’s law equation is what the electricity works against in an electrical circuit. Resistance is measured in ohms (Ω). Resistance can come in many forms, some good, some not so good. Every electrical circuit needs some form of resistance. If not, you have a short circuit, and we know what happens if we have one of those.

How does Ohm's law work?

Once you know the circuit, you know where the gas (voltage) is going and you can measure it at different points in the circuit to get a good idea of how the circuit is operating.

Why does heat increase resistance?

One is heat; the higher the temperature, the higher the resistance. The reason for this is that a heated substance has a lot of molecular movement, which affects electron flow. The harder it is for electrons to flow, the more resistance you have. That’s the layman’s definition of resistance. Distance can also affect resistance;

Can you use resistance testing on a coolant temp sensor?

On the other hand, if checking a coolant temp sensor, resistance testing is the way to go. Be sure to use resistance checks wisely when trying to find the effects of resistance in an auto electric system. Why not call Pop’s Auto Electric and solve auto electric system problem with the industry experts. There is a reason that other shops send electrical problems to Pop’s Auto Electric.

Does distance affect resistance?

Distance can also affect resistance ; the longer a wire is, the more resistance it has. Think back to our car with a tank of gas. We’re going to use more gas the farther we have to travel to get back to the negative battery post.

Effects

• Batteries will always have some resistance. Though the internal resistance may be or appear low, around 0.1Ω for an AA alkaline battery, and about 1Ω to 2Ω for a 9-volt alkaline battery, it can cause a noticeable drop in output voltage if a low-resistance load is attached to it.

See more on learningaboutelectronics.com

Example

Advantages

Performance

Variations

Applications