The most common cause of why cars can’t start is a dead battery. If you want to start your engine at the first click, your battery must always be fully charged. In this article, I’ll discuss the topic: how long to leave a car battery running to charge the battery?
You need to spend 10 to 12 hours fully charging your battery using the typical 4 to 8 (charging) amperes. If you want to start the engine with a dead battery faster, boost its charge first. This charge boosting could take from 2 to 4 hours.
You can also resurrect a dead battery by jumpstarting the engine. This will enable the alternator to start charging the battery. You should drive your car around or allow it to idle for about 30 minutes. This will help the alternator to continue charging the battery.
Read on to learn how long it will take to charge your battery if you leave your car running and how they usually do this.
How Long to Leave a Car Running to Charge the Battery?
If you use the usual 4 to 8 amperes to charge your battery, it will take 10 to 12 hours to do it thoroughly. You will be able to start the engine faster if you will boost the battery charging first. This will take you about 2 to 4 hours only.
Still, the best way to do it is to charge the battery slowly. You can also bring back the life of a dead battery by jumpstarting the engine. Once the engine is running, the alternator will then do its work of charging the battery.
To get a reasonable battery charge, drive your car around or let the engine run idle for about 30 minutes or more. A dead battery needs at least half an hour with its engine running to get a sufficient charge.
You can also bring a dead battery back to life if you jumpstart the engine. However, after starting the engine, you should keep it running so the battery charge will be sufficient. You can resuscitate your failing battery if you do this for at least 30 minutes.
Revving the engine faster will also charge the battery faster. The reason is that the more you rev the engine, the faster the belt turns the alternator. When the alternator turns faster, it produces more electricity, charging the battery more quickly.
What Affects Battery Charging Time?
Several factors can influence the speed you can charge a flat battery. It is the electric gadgets that your car uses that consume the electricity that the alternator and the battery generate.
The more electric gadgets you use, the faster your electricity consumption will be. In addition, the quicker your battery will discharge if the alternator is not wholly efficient. If the alternator is not working efficiently, the battery is forced to take up the energy slack.
Alternator and Battery Condition
In this regard, you should be mindful of the health of the alternator and the battery. You should always check the operational efficiency of the battery and the alternator. They should always be in tip-top shape because they work together to ensure the best engine operation.
If the battery is completely dead, it will take about 2 hours of running the engine or driving the car around to get it to charge about 80 percent.
However, to charge the battery at its optimum level, the alternator should be able to provide about 14 volts on the terminals of the battery as it is being charged.
The battery also requires the current to be around 60 amps or more. This amperage level is good for the electrical components that draw energy from the battery while driving your car to get it fully charged.
What Can Drain a Car Battery?
Here are the things that can discharge a battery:
- Parking the car and forgetting to turn off the headlights and other lights inside and outside of the vehicle, especially if done overnight.
- Problems in the electrical system or circuits drain the juices of the battery.
- Corrosion in the electrical system.
- Old or malfunctioning battery.
- General wear and tear
How Does a Car Charge Its Battery?
When the engine is running, the thing that charges the battery is the alternator. The alternator is the car part that produces power or electricity that charges the battery. It is the battery that provides the initial power to start the engine.
This is how the battery and the alternator work in tandem to get your car engine running. As soon as the battery gets the engine running, it goes to its regular work, and the alternator takes over, sustaining the energy needs of the battery.
In other words, the alternator is responsible for charging the battery. Its function is to ensure that the battery is always fully charged.
This is how it works: When you turn on the ignition, the battery will spend around 100 to 300 amperes starting the engine. This is the amount of current that the battery must regain to restore it to where it was before it started the engine.
This is the function of the alternator. It restores the energy that the battery spent in starting the engine. Once there are around 14 to 15 volts of continuous power from the alternator, and while the engine is on, its serpentine belt can do its job.
The job of the serpentine belt is to drive several peripheral car components, such as the alternator, the water pump, the air conditioning, and the power steering pump. If the voltage the alternator delivers to the battery drops to just one level or 13 volts, you need to replace the alternator.
Again, how long to leave a car running to charge the battery? Drive around or let the engine run for around 30 minutes to charge the battery.
How Long Will It Take for the Alternator to Recharge the Battery?
The alternator cannot revive a completely dead battery. Its work is to sustain the battery’s life to provide electricity to the vehicle’s electrical components. The battery also provides the initial power to start the starter to start the engine.
After the engine has started, the alternator provides the energy that the battery needs to supply the energy needs of the vehicle.
To efficiently do its job, the alternator must produce 14 to 15 volts of electricity to keep your car running. You need to replace your alternator if the voltage drops to 13 volts or less.
The alternator can only recharge a battery to a certain level, especially if the battery is completely dead. In this case, you must use an amp charger and charge the battery in advance. This will take around 15 to 30 minutes and provide a charge of 40 amps to the battery.
If you want to give a sufficient charge to your battery, you should continue driving your vehicle for at least 30 minutes.
Is It Better to Trickle Charge or Jumpstart?
The answer is that recharging the battery is better than jumpstarting the engine. It is only during emergencies that jumpstarting is better. Jump starting the engine will only enable your engine to start – so that the alternator can recharge the battery.
So, when the engine is already running, your battery will recharge itself. You should give at least half an hour to this process before safely disconnecting the booster battery from your previously dead but now resuscitated battery.
Jumpstarting your engine needs another car with a good battery and jumper cables. These cables are available at dealers of car supplies:
- Start by connecting the jumper cable’s positive (red) clamp to the positive terminal of the good battery to your battery’s positive (red) terminal.
- Connect the jumper cable’s negative (black) clamp to a metal part of your vehicle. This part should not be painted.
- Start the engine of the car with a good battery.
- After a couple of minutes, try to start your engine. If your engine starts, its alternator will begin recharging your flat battery.
- Give it at least 15 to 30 minutes to give your battery enough charge so that you can run your engine on its battery.
Again, after jumpstarting your engine, you should drive your car or allow its engine to run for at least 30 minutes so that the alternator can charge the battery at a good enough level. This will ensure you won’t be saddled with a dead battery soon after.
Can You Charge a Completely Dead Battery?
If there is no problem with your engine, it is entirely possible to resuscitate your battery, even if it is completely dead. Jumpstarting your car or using a battery charger can do the job of reviving your discharged battery.
When your battery recharges, allow your engine to run at idle. Switch off all the electrical gadgets of your car and let the engine idle for around 30 minutes to give your battery sufficient charge.
How Do You Know If the Battery Is Charging?
You can know the status of battery charging by looking at your dashboard. Observe the movement of the voltmeter. It must indicate a level of around 12.6 volts. You can also check the voltage at the battery terminals.
Get a multimeter and set it to the 14 to 15 voltage range. Poke the positive and negative probes of the multimeter to the respective positive and negative terminals of your battery. Your battery is successfully charged if the voltage reading is about 14 to 15 volts.
You can spend around 10 to 12 hours charging your battery using 4 to 8 amperes to charge a completely dead battery. If you want to start the engine faster, you have to boost the charging of the battery. It will take about 2 to 4 hours to do this.
By jumpstarting the engine, you can also bring back the life of your battery. The alternator will do its work of charging the battery. To charge the battery sufficiently, drive your car around or allow it to idle for about 30 minutes or more.