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How long to leave a car running to charge battery

SOLVED! How long to leave a car running to charge battery?

Did you encounter the question of how long does it take to leave the car running to charge its battery?

Well, the answers to that are discovered if you continue to scan underneath. We’ve also gathered several important pieces of information related to the topic of car batteries.

Furthermore, determinants on when to replace a dead battery, its lifespan, and the essential time needed to wait before it fully recharges are further discussed below.

What charges a car battery?

The alternator is the source of electricity to keep the battery charged while driving. This contains electromagnets driven from the serpentine belt that is why you can charge while it’s moving.

The serpentine will do its job once there are about 14-15 volts of continuous electricity from the alternator and the engine is also turned on. Any amount of voltage put out by less than 13 indicates that your alternator needs replacement.

How long does it take to leave the car running to charge its battery?

Since there are various electrical circuits inside the car that absorb power from the alternator, factors should be considered before charging.

Aside from the situation of electrical systems, the health of the battery and voltage produced by the alternator should be assessed.

If you have not been driving for a while, going out for 30 minutes will likely charge it. Although this does not fully recharge, the method keeps the battery from being completely dead.

In flat batteries, it could reach 80 percent in about 2 hours only. But, to reach its optimum level, the alternator should cope with around 14 volts on the battery terminals while it is charged.

The battery also demands a high current of electricity for about 60 amps or more. It works best and is beneficial for the components that draw power from the car’s battery while driving to make it fully charged.

How long to leave a car running to charge battery

Does a car battery charge while idling?

Fortunately, you may charge the car battery while the car is not in motion but the engine is running. The car battery will be managed by the alternator that supplies electricity to continue charging.

Considering if the engine is running, the battery should be charged on the process since the alternator is intact and meant to produce electricity.

However, it is a recommendation to drive instead and get on the road to completely charge it.

How long does it take for an alternator to recharge a dead battery?

Talking about a dead battery, the alternator could not revive such a thing. It gives too much workload to charge and maintain the life of the battery at the same time while driving.

Hence, the alternator can only offer to recharge flat batteries depending on the level of battery charging.

In this situation, the battery should be charged ahead of time through an amp charger. It requires 15-30 minutes of charging which then provides a 40 amp charge.

Then the alternator will continue the process while on the road. To recharge the battery, you should drive for half an hour.

How to determine if the car battery is charging?

How to determine if the car battery is charging

From the driver’s dashboard, take a look at the voltmeter. There must be a display of about 12.6 volts.
Another indicator that the car battery is successfully charging is when the black lead must be lined with the negative edge of the battery. While the red edge is linked to the positive side.

In addition, try to run the car engine. Then assess the battery terminals for voltage. The alternator is working properly when the voltage reads around 14-15 volts.

Note that a car battery can live up to 5 years, depending on how you maintain the car. But once it reaches the limit it will need replacement.

How often does one need to use a car to avoid draining the battery?

A car can remain parked for about a month without draining its battery. But for advanced featured cars which require an increased supply of power, your battery could die easily.

Many experts say that the basic lifespan of a car’s battery is up to 5 years, but battery death is difficult to predict.

It merely depends on the factors such as the age of the battery, how often you take a drive, and the weather or climate that you live in.

The best option to apply is to charge the battery regularly like every two to three days interval. An important thing is being able to fully charge the battery while driving and not idle.

How to recognize the time for car battery replacement?

How to recognize the time for car battery replacement

A well-maintained battery at least survives 3 to 5 years of usage. But if it needs replacement, here are several signs that you could observe.

The first sign is the engine’s too slow to start because the internal parts of the battery have already worn out.
The second sign is when you experience electrical issues while driving. Take the dimmed front or backlights, faulty radio, and non-functioning dashboard as an example.

Thirdly, observe the connectors of the battery if it’s rusty or torn already. This damages the connection which makes it hard to start up the car. You can clean the wires with sandpaper, but wear gloves.

The last sign is the extreme weather condition. Living in multiple seasons or experiencing heavy weather could damage the battery.

Extra information, check the receipt and warranty of the battery to determine whether it is too old and needs replacement.


As a car owner, you should recognize problems like a draining or dead battery. The battery and alternator are both essential to keep your car alive, which then needs to be well-maintained.

Hopefully, you already understood how long it takes to leave the car running to charge its battery.

Keep the knowledge intact all the time, monitor the health of your battery, and keep safe while driving.

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