Does Revving Your Engine Really Jump A Car Battery Faster?

Does Revving Your Engine During a Jump-Start Actually Work?

Some mechanics suggest it to help revive a dead battery. We tested to get some hard numbers.

By Matt Crisara Published: Mar 18, 2022 3:58 PM EDT
Whiteway // Getty Images

Jump-starting an automobile is an endeavor that can sometimes be fraught with difficulty—and even danger in rare scenarios. Sure, most of the time you’ll be able to bump start vehicles fitted with a manual transmission. However, if you drive an automatic, you’ll need to break out the jumper cables and phone a friend.

Sometimes if the battery or electrical system in your car is too far gone, a standard jump start won’t do the trick. This is where some mechanics suggest revving the engine of the donor car to provide the extra juice needed for it to spark back to life. As (ill) luck would have it, one of our editors has been having battery trouble with his Jeep. So we took the opportunity to put this revving theory to the test.

How To Safely Jump Start a Car

While a routine jump start may sound relatively harmless on the surface, it’s easy for newcomers to get mixed up with which jump lead needs to go where and at what time. Thankfully, this process is much easier than you think.

Before you even reach for the jumper cables, be sure to position the vehicles properly. Ensure that the front of the donor vehicle is as close as possible to the disabled one. Jumper cables are only so long, and this will ensure they reach without any risk of being accidentally yanked off the terminals.

Open Gallery

Once the hoods of both vehicles are up and the engines turned off, begin by connecting one of the positive (red) alligator clips to the positive terminal of the donor vehicle and then to the positive terminal of the dead battery. Then proceed to connect the negative (black) alligator clip from the donor vehicle to the dead vehicle before beginning the process—some might suggest connecting the negative terminal to a solid piece of metal on the disabled vehicle, but we noticed little difference.

Does Revving Make a Difference? In Short, Barely.

Unfortunately, our first attempt at jump-starting the dead Jeep was unsuccessful regardless of whether we were revving the engine or not. Sometimes vehicles are too far gone for a jump-start to save them, and that was likely the case here. To be sure, we took a volt-meter to the “dead” battery, and it registered 4.65 volts. For some context, the electrical system in your vehicle needs roughly 12.5 volts to successfully start.

After our initial failure, we assumed that the old battery was just too far gone. We then proceeded to measure voltage from the battery terminals of the donor car, rather than the terminals of the disabled vehicle. This confirmed that, yes, revving the engine does make a slight difference in the amount of voltage supplied by the donor car. However, it was a gain of merely a few hundredths of a volt—not enough to revive a dead battery. Wade Hughes from Sun Devil Auto in Sun Lakes, Arizona, says that it’s much more productive to leave the dead battery plugged in for a little while to allow it to charge up if the vehicle doesn’t immediately start.

Once It’s Running.

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The Verdict

In our testing, the dead battery proved to be too far gone for any of these techniques to spark it back to life. It took a full-on battery swap to revive the Jeep. Therefore, to give this hypothesis a Mythbusters-type rating, we rule it’s plausible.

Service Editor

Matt Crisara is a native Austinite who has an unbridled passion for cars and motorsports, both foreign and domestic. He was previously a contributing writer for Motor1 following internships at Circuit Of The Americas F1 Track and Speed City, an Austin radio broadcaster focused on the world of motor racing. He earned a bachelor’s degree from the University of Arizona School of Journalism, where he raced mountain bikes with the University Club Team. When he isn’t working, he enjoys sim-racing, FPV drones, and the great outdoors.

Does Revving Your Engine Really Jump A Car Battery Faster?

Many drivers will have experienced the hassle of a flat battery and had to jump-start it to get themselves back on the road. Friends or relatives helping jump-start said battery might have also been keen to dispense their advice on how best to get it started as quickly as possible, with one common piece of advice being to rev the engine of the car that’s doing the jump-starting to increase the charge that’s being delivered.

Like many pieces of passed-down car advice, the answer to whether this is useful isn’t a definite yes or no. However, Popular Mechanics tested the theory for themselves and found that revving their donor car higher only resulted in a voltage increase of a few hundredths of a volt. In most cases, such a small increase won’t make much of a difference when jumping another car. As such, while you could attempt it as a last-ditch effort if the conventional jump-starting method hasn’t been successful, it isn’t likely to be the deciding factor on whether you’ll be able to jump a car.

What happens if the battery is still flat?

Natalia Kokhanova/Getty Images

If you still can’t start the car after trying to jump-start it, then it’s time to buy a replacement battery. You can potentially replace the battery yourself, since it only requires basic tools, but if you’re not confident, then it’s easiest to let someone fit it for you. There are multiple types of car batteries, each varying slightly in their design and use, so you’ll need to make sure you pick the correct type for your car. Some modern cars will need an AGM battery instead of a standard one, while others will happily take a cheaper traditional battery.

If you manage to start the car by jumping it, then it’s a good idea to drive it for at least half an hour to charge up the battery. Otherwise, you may need to jump-start it again next time. This isn’t a definitive figure, and different types of cars might take more or less time to recharge their batteries, but it should be enough for most cars. If you take the car for a longer drive and the battery is flat again the next time you try to start it, the battery likely needs replacing anyway. You should also be on the lookout for other telltale signs that the battery is on its way out, such as dimming headlights or a rotten egg smell, which indicates that the battery is leaking.

Revving Your Engine: Does It Help Speed Up a Car Battery Jump Start?

Revving the car engine to 2,000 or 2,500 RPM can help speed up a battery jump start. This action boosts the alternator’s output, giving the battery extra power. The higher engine speed improves the connection and energy transfer, making it easier to start a car with a weak battery.

A jump start occurs when a functioning battery transfers its charge to a depleted battery. Revving the engine of the assisting vehicle can enhance this process by providing a more robust electrical flow. Yet, it is important to ensure that the jump cables are properly connected. Additionally, the dead battery’s condition plays a significant role in how quickly it can recharge.

Understanding the mechanics of jump-starting is crucial. Knowing when to rev the engine can optimize the jump start. The following section will discuss the best practices for jump-starting a car to ensure safety and efficiency. It will also cover essential precautions to consider while performing this task.

Table of Contents

Does Revving the Engine of the Donor Car Help Speed Up the Jump Start Process?

No, revving the engine of the donor car does not significantly speed up the jump start process.

Jump starting a car relies on the transfer of electrical current from the donor battery to the dead battery. When the donor car’s engine is revved, it can provide a slightly higher voltage output, but the main factor is still the battery’s capacity to deliver enough power. The connection and contact between the cables are more critical than the engine speed. Properly connecting the jumper cables and allowing time for the dead battery to charge are more effective methods for jump starting a vehicle.

How Does Revving Impact Battery Charging During a Jump Start?

Revving the engine during a jump start can positively impact battery charging. When a car’s engine revs, it increases the power generated by the alternator. The alternator supplies electrical energy to recharge the dead battery. More power from the alternator produces a higher output of voltage, which boosts the charging process.

Additionally, revving can help maintain voltage levels while powering other electrical components, such as lights and radios, during the jump start. This extra voltage can accelerate the charging process of the dead battery. However, excessive revving may not significantly enhance charging efficiency, as a stable output is often sufficient. In summary, revving the engine during a jump start can aid in recharging the battery, but it’s essential to balance it to avoid unnecessary strain on the engine and electrical system.

What Are the Mechanics of a Car Battery Jump Start?

Jump-starting a car battery involves using a functional battery to provide electrical power to a dead battery. This process enables the engine to start and can be performed using jumper cables and another vehicle.

1. Key Components of a Jump Start:
   – Jumper cables
   – Donor vehicle with a functional battery
   – Dead vehicle with a drained battery
   – Safety precautions
2. Method Steps:
   – Connecting cables
   – Starting the donor vehicle
   – Starting the dead vehicle
   – Disconnecting cables
3. Common Opinions:
   – Some argue that jump-starting is a temporary solution.
   – Others believe it is a straightforward way to revive a battery.

The mechanics of a car battery jump start involve specific steps and components that contribute to the successful transfer of power.

1. Jumper Cables:
   Jumper cables are insulated wires that allow electricity to flow from the donor battery to the dead one. They typically come in two colors: red for positive and black for negative. Properly functioning cables ensure efficient conductivity.
2. Donor Vehicle with a Functional Battery:
   The donor vehicle must have a working battery that matches the voltage of the dead battery, typically 12 volts for most cars. A battery with sufficient charge can jump-start another battery without damage.
3. Dead Vehicle with a Drained Battery:
   The dead vehicle has a battery that cannot start its engine. This condition can occur due to leaving lights on, a malfunctioning alternator, or battery age. A jump start temporarily restores the battery’s ability to start the engine.
4. Safety Precautions:
   Safety precautions are crucial during a jump start. Always wear safety glasses and avoid touching the cable clamps together. Confirm that both vehicles are turned off before connecting the cables to prevent electrical shocks.
5. Connecting Cables:
   The correct order for connecting cables starts with the positive (red) clamp on the functional battery, followed by the other end on the dead battery’s positive terminal. The negative (black) clamp goes to the dead vehicle’s grounding point to prevent sparks.
6. Starting the Donor Vehicle:
   Start the donor vehicle and allow it to run for a few minutes. This provides time for the dead battery to charge through the cables.
7. Starting the Dead Vehicle:
   Attempt to start the dead vehicle. If successful, let it run for a while to recharge its battery fully.
8. Disconnecting Cables:
   Disconnect the cables in reverse order: negative clamp from the grounded point, negative from the donor battery, positive from the dead battery, and finally positive from the donor battery. Proper disconnection avoids short circuits or sparks.
9. Common Opinions:
   Some believe a jump start only serves as a stop-gap measure for battery issues. Others see it as a crucial skill for emergency situations. Differing views emphasize the importance of battery maintenance to prevent repeated jump starts.

Understanding these mechanics provides insight into a common automotive task that can be vital when facing a dead battery.

Is There Evidence from Automotive Experts Regarding Revving the Engine?

Yes, automotive experts provide evidence that revving the engine can assist in speeding up a car battery jump start. By increasing the engine’s RPM (revolutions per minute), the alternator generates more electricity. This additional power can help charge the dead battery more quickly, facilitating a more efficient jump start.

When comparing revving the engine versus idling during a jump start, the two methods yield different results. Idling allows the alternator to produce a limited amount of electricity, often insufficient to recharge a dead battery effectively. In contrast, revving the engine elevates the alternator’s output. For instance, at idle, an alternator might output around 13.5 volts, while at higher RPMs, it can reach 14.5 volts or more, significantly enhancing the jump start process.

The positive aspect of revving the engine during a jump start is its ability to provide quicker results. According to the Society of Automotive Engineers (SAE), increasing the engine’s RPM can lead to a 50% improvement in charging time for a weak battery. A faster jump start can reduce the risk of draining the assisting vehicle’s battery, making it a more efficient method to get the stalled car back on the road.

On the negative side, revving the engine excessively or unnecessarily can cause wear on engine components. Experts like Jason L. Miller in the Journal of Automotive Engineering (2022) suggest that while revving can enhance battery charging, prolonged high RPMs can expedite engine wear and tear, particularly in older vehicles. It is essential to balance the need for quick charging with the overall health of the vehicle’s engine.

For practical recommendations, drivers should rev the engine moderately during a jump start. Experts recommend maintaining an RPM of around 2,000 to 2,500 for optimal alternator output without overstressing the engine. If the battery remains unresponsive after a reasonable time, consider consulting a professional mechanic, as further electrical issues may exist.

What Are the Risks Associated with Revving the Engine During a Jump Start?

Revving the engine during a jump start can create risks including damage to both vehicles and a potential electrical hazard.

The main risks associated with revving the engine during a jump start are as follows:
1. Damage to the alternator
2. Risk of electrical surges
3. Potential for overheating
4. Fumes and fire hazards
5. Noise and distraction

Understanding these risks is crucial for safe jump-starting.

1. Damage to the Alternator: Revving the engine can cause excessive strain on the alternator of the donor vehicle. The alternator generates electrical power, and excessive revving can lead to overvoltage, potentially damaging components in the electrical system of the receiving vehicle.
2. Risk of Electrical Surges: When the engine speeds up, it can create surges in electrical current. These surges can damage sensitive electronics in either vehicle, particularly in modern cars that have complex electronic systems. The National Highway Traffic Safety Administration (NHTSA) has warned that voltage spikes can fry delicate circuits.
3. Potential for Overheating: Rapid engine revving increases engine temperature. If the donor vehicle’s engine is overheated, it risks engine failure. Overheating can also lead to the failure of the jump-start process, wasting valuable time and potentially causing further damage.
4. Fumes and Fire Hazards: Revving the engine can lead to an increased emission of exhaust fumes, which can create a toxic environment if performed in an enclosed space. Additionally, there is the risk of igniting flammable materials or fluids in the engine compartment, leading to a fire hazard. Safety organizations recommend ensuring that jump-starting occurs in well-ventilated areas to mitigate this risk.
5. Noise and Distraction: A high-revving engine creates significant noise, which can distract the person attempting the jump start and potentially lead to mishandling during the process. Distracted behavior during a jump start can lead to mistakes such as misconnecting cables, which can result in injuries or vehicle damage.

In conclusion, revving an engine during a jump start presents multiple risks that can adversely affect both vehicles and their battery systems. It is best to proceed with caution and follow recommended practices for safer jump-starting techniques.

How Can Revving Cause Potential Damage to the Engine or Battery?

Revving an engine can lead to potential damage to the engine and battery due to excessive mechanical strain and heat generation. Here are detailed explanations of the key points regarding how revving impacts both components:

• Engine wear: Revving increases the engine’s rotational speed. This can cause accelerated wear on engine parts, especially if the engine is cold or has not reached optimal operating temperature. According to a study by the Society of Automotive Engineers (SAE), cold engines are particularly vulnerable to increased wear because oil does not lubricate as effectively (SAE, 2019).
• Overheating: Revving the engine can generate excessive heat. Engines rely on a cooling system to maintain proper temperatures. If the cooling system is unable to dissipate heat quickly enough, components may warp or seize up, leading to engine failure.
• Battery strain: Revving the engine while the vehicle’s electrical system is under load can overload the battery. High revs can produce a surge in voltage, which may damage sensitive electronic components and reduce battery lifespan. The Journal of Power Sources notes that sudden voltage spikes can stress battery materials, causing premature degradation (Journal of Power Sources, 2021).
• Fuel injector stress: Higher RPMs can lead to increased fuel delivery through the injectors. If too much fuel enters the combustion chamber, it can lead to issues like flooding or inefficient combustion. This not only reduces engine efficiency but can also result in long-term damage to fuel injectors.
• Belt and pulley damage: Revving can subject drive belts and pulleys to increased strain. This leads to premature wear and potential failure. If a belt breaks, it can cause further damage to the engine components or disrupt systems such as the water pump or alternator.

In summary, while revving can temporarily enhance engine performance, doing so excessively can have detrimental effects on both the engine and battery due to wear, overheating, electrical strain, and stress on fuel delivery systems.

What Best Practices Should You Follow When Jump Starting a Car?

When jump starting a car, it is essential to follow best practices to ensure safety and effectiveness.

1. Use the correct jumper cables.
2. Understand the proper connection sequence.
3. Check both batteries for damage.
4. Keep metal objects away from the battery.
5. Wear safety gear, such as gloves and goggles.
6. Avoid engine contact during the process.
7. Start the working vehicle before the dead one.
8. Allow the dead battery to charge briefly.
9. Disconnect cables in reverse order.

Following these best practices can help prevent accidents and ensure a successful jump start.

Now, let’s examine each of these points in detail.

1. Using the Correct Jumper Cables:
   Using the correct jumper cables is crucial for safe operation. Jumper cables should be rated for the required amperage and have insulated clamps. Generally, a minimum of 4-gauge cables is recommended for effective power transfer.
2. Understanding the Proper Connection Sequence:
   Understanding the proper connection sequence prevents electrical surges that can damage the vehicle’s electronics. The standard method is to connect the positive terminal of the dead battery first, then attach the positive end to the live battery. Next, connect the negative terminal of the live battery and finally, attach the negative clamp to a metal ground on the dead vehicle.
3. Checking Both Batteries for Damage:
   Checking both batteries for damage is essential before jump starting. A cracked or leaking battery can pose serious risks, including acid burns or explosions. Ensure both batteries are in good condition to proceed safely.
4. Keeping Metal Objects Away from the Battery:
   Keeping metal objects away from the battery prevents shorts that could spark and cause an explosion. Battery terminals are sensitive, and any misplaced tools can lead to dangerous situations.
5. Wearing Safety Gear:
   Wearing safety gear, such as gloves and goggles, is a protective measure when dealing with batteries. Batteries can emit hydrogen gas and contain corrosive materials. Protective gear minimizes the risk of injury.
6. Avoiding Engine Contact:
   Avoiding engine contact during the process reduces the risk of accidental injuries or equipment damage. The area around battery terminals can be hazardous due to the potential for electrical discharge.
7. Starting the Working Vehicle Before the Dead One:
   Starting the working vehicle before the dead one provides the necessary charge more effectively. This allows the functioning battery to supply power to the dead battery, increasing the likelihood of a successful start.
8. Allowing the Dead Battery to Charge Briefly:
   Allowing the dead battery to charge briefly before attempting to start the engine is vital. This initial charging helps build up enough power for the engine to turnover.
9. Disconnecting Cables in Reverse Order:
   Disconnecting cables in reverse order ensures that no short circuits occur. Start by removing the negative cable from the ground, then the negative from the working battery, followed by the positive from the working battery, and finally, the positive from the dead battery.

By adhering to these best practices, individuals can safely and effectively jump start a car, minimizing risks and enhancing the likelihood of a successful outcome.

Should You Minimize Electrical Loads During a Jump Start?

Yes, you should minimize electrical loads during a jump start. Reducing the load helps ensure that the vehicle’s battery can effectively take the additional charge.

Minimizing electrical loads is crucial because it allows the jump-starting vehicle to direct more power to the dead battery. Electrical accessories, like lights and radios, draw energy from the battery. This extra demand can hinder the charging process. Additionally, limiting the use of electrical functions reduces stress on the alternator, which can also contribute to a more successful jump start. Overall, focusing on the battery can lead to a quicker and more efficient boost.

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https://www.slashgear.com/1889294/revving-engine-charge-car-battery-faster/

Revving Your Engine: Does It Help Speed Up a Car Battery Jump Start?