Finding out that you have a dead or dying battery will always happen at the most inconvenient time when you just needed to get somewhere fast. You will have heard that you can start revving the engine to charge battery faster, but just how true is this?
Here’s the short answer first, followed by more detail regards what people say about the damage from revving an engine in park or neutral.
Does revving the engine charge the battery?Yes, revving the engine can charge your battery faster, but only when the battery is nearly dead and close to being depleted of power. Revving will accelerate the crankshaft’s rotation, so in theory speeds up the rate of energy conversion to the battery.
There’s more to it than that though, and some warnings below on how long you should rev the engine to charge your battery.
Revving your car’s engine to charge the battery
A car’s charging system ensures the battery always has a suitable power supply providing you keep the car on the road and drive it regularly. Because of that, revving your engine when you get into the car isn’t going to have an effect.
However, in cases where the battery is dead or nearly depleted, you might find you can charge it quicker by revving the engine. I’ve read a note from a mechanic who recommends you keep the revs between 1,500 and 2,500 RPM.
There is some theory behind this though. I saw this statement on a Reddit thread when someone asked whether revving the engine charge the battery faster:
“When a car is running, the engine crankshaft is in motion. A belt goes from the engine crankshaft to a pulley attached directly to the alternator, which converts the mechanical energy from the crankshaft spinning into electrical energy to recharge the car battery. Since revving your engine (even in neutral) accelerates the engine crankshaft’s rotation, this increases the rate of mechanical energy conversion into electrical energy and should in theory charge the battery faster.”
That makes a lot of sense to me.
Revolutions of the alternator are directly proportional to the engine’s revolutions, meaning the faster the engine turns, the more electricity the alternator produces. With a dead battery running the car at idle speed, it will take forever to charge it if the alternator manages to charge it at all.
Keep in mind that revving your engine to charge the battery while the car is not moving isn’t healthy for the engine, so make sure not to go over 2,500 RPM.
Handy Hint: I analyzed the top speeds of the modern Honda Civics to see which once can go the fastest 0 to 60 mph.
How long to rev engine to charge battery?
From what I can gather, it’s not recommended that you rev the engine to charge the batter any longer than for 5 minutes.
Once your car gets moving, it’s preferable that you drive for between 20 and 30 minutes to get the battery charged up quicker.
When to rev the engine to charge the battery
Here are the specific scenarios in which it’s beneficial to rev your engine to charge the battery.
The most common reason for a dead battery is when starting your car for the first time in the morning. This problem can arise when an old battery meets cold weather, or it just means that you forgot to turn something off the night before, such as the lights or the radio.
Here is what you can do to get your car going.
Does revving your engine help jump batteryor jump-start another car?
Suppose you turn your key to the on position and see no dashboard lights. In that case, it means your battery is almost at a 0% charge and trying to push start probably won’t work.
Jumper cables are your safest bet in a scenario like this. Once you connect your battery with another car, revving the donor car will significantly increase the charging rate of your dead battery.
Again, make sure you keep it under 2,500 RPM. After a couple of minutes, your car should be able to start depending on the size difference between the two vehicles. After you start your car, you should keep your car’s RPM above idle speed for about 5 minutes, and after you take it for a short drive, the battery could be back to enough power.
Push starting a car with a dead battery
In a case where your battery still has some charge but not enough to turn the engine over, you can try and push start it, but only if your manufacturer allows that.
Push starting a car might void the warranty in some vehicles and cause potential damage. Each car is different on this matter, so make sure to check that for your specific engine and model.
After you start your car this way, you can take it for a short drive right away, or you could rev the engine while the vehicle is standing still. Still, taking it for a short drive is much healthier since that won’t be a problem in this case.
Book an electrical diagnosis if you get regular dead batteries
Suppose you wake up to a dead battery regularly, every morning or a couple of times a week, and you are sure you turned all the auxiliaries off.
In that case, there is most probably a faulty electronic component that keeps draining your battery even when the car is off. A thorough electrical diagnosis will help you find the culprit.
On the other hand, a faulty alternator will be easy to notice since your car will lose electricity while driving and ultimately stop. It could also happen that your car works fine while connected to another running vehicle but dies after it’s disconnected.
If you find yourself in some scenarios where revving the engine is beneficial, ensure you keep to the mentioned instructions. Not adhering to them can cause many problems since a car isn’t designed to stand still while running for prolonged periods, especially not running above idle speed.
Issues that can arise are overheating, and an engine not getting sufficient lubrication, both of which can cause catastrophic damage.
Battery problems aren’t limited to not having enough electricity. A battery can also be overcharged, which is much more harmful than being depleted of power. Here are some symptoms to look out for if you suspect this might be a problem with your car.
- Burning wires, smell, or smoke.
- The smell of sulfuric acid.
- Interior lights are noticeably brighter than usual.
- Whining noises that increase with engine revs.
- Battery warning light.
The cause of overcharging is always the alternator, but it doesn’t mean you need to replace the whole unit. All alternators have an integrated voltage regulator that limits or increases the power going to the battery.
If you notice these symptoms, the voltage regulator is often the culprit. It will be a lot cheaper to repair than replace the alternator.
Does revving the engine help jump-start another car?
Revving the car that is trying to jump-start another does help. Make sure not to floor the throttle, but a light input keeping the car roughly 1,000 RPM above idle will do the trick just fine.
Does revving the engine make the car warm up faster?
Based on what we now know, revving the engine can help make the car warm up faster if the battery is low on power. The better solution is to get driving, as once the wheels start turning, after 20 minutes, your battery will be very well powered again.
How long should I idle my car to charge the battery?
Keeping your car at idle speed to charge the battery will take around 15 minutes on average, but I don’t recommend that. Slightly revving your car for a couple of minutes and taking it for a short drive after letting it idle is a much safer way to do it.
You can read all thepros and cons of battery charging by idling here.
Does revving the engine in park damage it?
It doesn’t have to if you keep the RPM not much above idle speed and don’t do it for longer than 5 minutes. Anything more than this can substantially damage your engine.
A dying battery will typically happens when you wake up one morning and just want to get going. Thankfully it might be relatively simple to solve if you can still rev the engine a little to get some charge into the battery.
More simple car guides…
- What to do if the battery dies as you’re driving
Image in header via https://pixabay.com/photos/car-driving-gas-brake-clutch-824074/
How long does it take to rev an engine to charge a battery? ›
Remember: After you've done a jump start, you'll need to keep the vehicle's engine running for around 30 minutes to allow the alternator time to charge the battery sufficiently.How far do you have to drive to charge a battery? ›
If you want to get a full charge from a drive, you will need to drive at least half an hour on highway speeds. This is about 30 to 40 miles. You can also idle your car to get power, but it will take a far longer time.Will idling car 20 minutes charge battery? ›
If you're not going to be driving the car, just idling the car will do your battery more harm than good. Starting a car draws 100 to 300 amps to start a car and idling a car for 15-20 minutes will only replace 3-4 amps, the car battery never gets fully charged.Will a battery charge while idling? ›
The simple answer to this question is yes, your car's battery will start to charge as long as your engine is running. As long as the electrical systems aren't draining the battery quicker than the alternator is charging it, it is technically possible to completely charge your battery using this method.Does revving the engine help jump start another car? ›
Increasing the engine speed on the donor vehicle makes sure enough amperage (current) flows to the weak battery. Yes, it is helpful to rev the engine and hold it around 1,200 rpm.Does a car battery recharge itself while driving? ›
Can a car battery recharge itself? Sometimes, yes. When you drive, your car battery is kept recharged, either by an alternator on modern cars, or by a dynamo on earlier cars. So if it's been flat and you've managed to jump start it, driving it will actually recharge the battery.Is 2 hours enough to charge a car battery? ›
A normal-sized car battery can be fully charged in 2 to 4 hours with a 20 Amp charger, and with a 4Amp charger, it takes around 12 to 24 hours. You can also jumpstart your car's battery using another vehicle.What can drain a car battery when the car is off? ›
What may drain a car battery when it's off are things such as interior lights, door lights, or even bad relays. While your engine runs, the alternator recharges the battery — which is why you typically don't have to worry about the battery dying while you're blasting the radio on your drive to work!Does revving charge battery faster? ›
The battery will charge faster if you rev the engine faster. Why? Because the faster the crankshaft turns, the faster it turns the belt that runs the alternator. And the faster the alternator turns, the more electricity it produces to run all the electrical stuff in the car — and recharge the battery.Is it better to idle or drive to charge battery? ›
A: One of the worst things you can do for your car is to start it and just let it idle. The oil will become contaminated and it really doesn't do much to keep the battery charged. You are much better off driving the car for 20 to 30 minutes every three weeks. This will help exercise all of the components in the car.
Can I leave my car idling for 30 minutes? ›
In a vacuum (and with infinite fuel), your engine would continue to run forever. But in reality, several things might occur if your car idles for too long. To avoid running your car for too long, you should only idle your vehicle for a few minutes at most before either moving your vehicle or turning the engine off.How long should I drive my car after a jump start? ›
How Long Does It Take To Charge A Car Battery? If you have jump-started your car, it is recommended to let your vehicle run for at least 30 minutes because it would typically require at least half an hour to charge a dead battery entirely or at least sufficiently.How long can you idle before battery dies? ›
Typically, your car can sit about four weeks to two months without driving before the battery dies. The reason your car can sit only for so long before it dies is the fact that your car battery is in use even when you're not behind the wheel.How long does dead car battery take to charge? ›
Charging a regular car battery with a typical charge amp of around 4-8 amperes will take about 10-24 hours to charge it fully. To boost your battery enough to be able to start the engine, it would take around 2-4 hours. The best way to maintain a long life for your car battery is by recharging it slowly.Is it OK to jump a car multiple times? ›
Jump-starting your car battery once is not a problem. However, if you have to jump-start your battery up to three times a week, it's time to get a replacement, as it is probably damaged. Also, when jumping-start a car, avoid cranking it more than three times if the car refuses to start.How long should a jump-start take? ›
How Long Does It Take to Jump a Car? If you're going to jump-start your car by yourself, you can expect the process to take about 10-15 minutes. If you have a professional jump-start your car, then it might take a little less time.How do you know when a car battery is fully charged? ›
To check the voltage you'll need a voltmeter, which can be purchased cheaply from most major automotive parts stores. Check the voltage of your battery using the voltmeter to help determine your next course of action. 12.6V volts or above - Your battery is healthy and fully charged. No further action is required.What RPM should I charge my car battery? ›
If your car was dead and you just received a boost the most acceptable answer for most vehicles is 2000 RPM. While you're driving and come to a red light, put the car in neutral and keep it around 1500 RPM. If you drive for at least 30 mins your car should be fine the next day when you start your car.Is 1 hour enough to charge a car battery? ›
NRMA's advice for a standard battery is “around 30 minutes.” This is because a car's alternator operates at between 50 and 100A, thus charges a battery relatively quickly. We don't recommend using jumper cables for starting most modern cars.Is 5 minutes enough to charge a car battery? ›
There is one big catch, however: While the batteries can technically be fully charged in just five minutes, electric car chargers currently in use today wouldn't be powerful enough to juice them up in that amount of time.
What kills your car battery the most? ›
- SELF DISCHARGE. ...
- CONTINUAL POWER DRAW, WHEN PARKED. ...
- OPENING THE DOORS / TRUNK. ...
- LEAVING YOUR KEY CLOSE TO YOUR CAR. ...
- YOU'RE TAKING TOO MANY SHORT DRIVES. ...
- PARASITIC DRAIN. ...
- ALTERNATOR FAULT. ...
- COLD WEATHER.
“Electrical devices or lights left running, a defective charging system or alternator, and extreme weather are some common reasons but maybe it's just time to get a new battery.”How do you tell if it's your battery or alternator? ›
Jumpstart your car. If you can turn the engine on, but it dies shortly thereafter, your car alternator likely isn't able to charge the battery. On the other hand, if you jumpstart the car and later on it fails to start on its own, it's likely a dead battery.At what RPM does a car alternator start charging? ›
For battery charging to occur, the alternator's voltage must exceed the battery's voltage. Alternator may not generate sufficient charging voltage until alternator speed is greater than about 2000 RPM.Is there a way to charge battery faster? ›
Get a heavy-duty fast charging cable
If you find your phone is charging too slowly even with the wall charger, consider a heavier-gauge cable. Some heavier-gauge cables are even branded as "fast chargers," which can help reduce charging times in both iPhone and Android phones.
Generally, if you can keep your engine RPM up, your alternator will charge your battery at a faster rate. If you are driving on a motorway, you should be able to charge your car battery in 30 minutes. If you are driving in the city, it may take an hour or more.How long does it take to charge a car battery with car idling? ›
Idling: it's far from ideal.
While idling older vehicles for 15-20 minutes may give them enough of a charge to restart, this approach is generally not recommended. Many modern cars are equipped with sophisticated battery management systems that are designed to help extend battery life.
Most car batteries will last between 500 and 1,000 charging cycles, which works out to a lifespan of between three and five years, depending on driving and weather conditions. While there's no way to make your car battery last forever, you can prolong its life as long as possible by caring for it properly.How much gas does AC use while parked? ›
How Much Gas Does a Car's Air Conditioner Use? Switching on your car's air conditioning system will use some gas. There are estimates that the air conditioning system will lower mileage by about 3 MPG.How much gas does idling with AC use? ›
Idling uses up to ½ gallon of fuel per hour (although it varies depending on the type and size of the engine). It may not seem like much, but idling for a few minutes everyday can cost you several dollars per week. MYTH: Engines need to warm up by idling, especially in cold weather.
Do you waste gas if your car is on and parked? ›
Wastes gas. Leaving your engine running consumes gasoline. As a matter of fact, allowing your car to idle for two minutes is equivalent of driving a mile. You can waste almost a gallon of gas if you leave your car idling for more than an hour.Does just running the engine charge the battery? ›
Lastly, you may have heard that idling your car for 15-20 minutes is a good alternative method to recharge your battery. While idling older vehicles for 15-20 minutes may give them enough of a charge to restart, this approach is generally not recommended.What tells the alternator to start charging? ›
These systems are controlled by the vehicle Engine Control Unit (ECU). As the vehicle demands more load the ECU sends a signal to the alternator requesting it to start charging. The alternator has to cope with varying electrical loads and adjust its charge rate accordingly.Does sitting with engine on drain battery? ›
If you do leave your car running for too long, you might experience a few unpleasant side effects: As mentioned, your car's engine continues to consume fuel so long as it's powered on. But it also consumes power from your car's battery because the engine and alternator both run slowly whenever your car idles.Will a car battery recharge itself overnight? ›
No. A dead car battery can't recharge itself. To get it charged and working, you could take it out and charge it or jumpstart it with another battery or another car. There's no type of car battery that can charge itself without external help.