It is tough to know how long to leave your car running to charge the battery properly. You want to make sure that the battery starts the engine next time, too.
Knowing how long to leave jumper cables or a battery charger on can be difficult to tell - and difficult to finish especially when you are in a rush. So how long do you need to let your vehicle run?
Ideally, you should either drive the car or leave it running for about 20 to 30 minutes to gain some level of charge in your battery. Idling for the same amount of time does help your battery have a better chance of starting later too.
We’ll dig in and consider the differences between older and newer vehicles as well as older and newer batteries. Also, let’s explore the real difference between idling the vehicle to charge the battery and driving it around. Does it matter?
Our information is sourced from the personal experience of driving vehicles that had potential battery issues and trusted vehicle sources from the Internet.
Is it ok to leave the car running for a shorter time?
Yes, you just have a higher risk of the car not starting the next time you try. Bring a well charged jump pack with or park in a place where your vehicle is accessible to jumper cables.
How long should I leave my car running to charge the battery properly?
So you’ve got your vehicle running after using jumper cables or a separate battery pack. This is a good start and an indicator that the battery does work - and so does your car. The next step is to know how long to let the car run to allow the battery to charge. The best answer is to drive around for 20 to 30 minutes to get the vehicle the best chance to charge the battery without wasting too much time or idling too much. We hope your commute or trip is about 20-30 minutes to make the best of this!
Should I let my car idle while charging?
Let’s assume that you disconnect the battery pack or other vehicle battery from your vehicle and it remains running. There are a couple of scenarios that determine whether or not your vehicle’s battery continues to charge.
Your vehicle has a working alternator
Your vehicle’s alternator is a very important part of making your vehicle start and run properly. The alternator converts mechanical energy from your the vehicle’s drive belt into storable electrical energy that restores your battery. Without this, your battery can drain rapidly and quickly fail to work, especially in extreme weather like hot or cold.
Completely charging the vehicle while using the alternator should take around an hour, though completely charging the battery after jumping it isn’t totally necessary.
Is it ok to partially charge my vehicle’s battery?
Yes. If you don’t have to drive an hour to get to your destination and you have no particular motivation to keep driving, you’ll be OK to drive a shorter time period just to get enough juice in your battery to keep going.
Your vehicle’s alternator isn’t working well
If your vehicle’s alternator is not working well, the initial jump start or charge won’t matter much. The battery won’t maintain a charge without a proper working alternator.
There are symptoms of a poorly working alternator, and they likely led up to the moment when your battery needed a jump:
- Dim llights
- Slow working electrical accessories
- Hard to start, or rough idle
- Battery warning light
- Potential whining or growling sounds
- Smell of burning rubber
No amount of driving will help a vehicle’s alternator. You’ll want to get the vehicle into the shop. You should still be able to start the vehicle with a jump start, but it might not go very far.
Is there a difference between charging with jumper cables on and driving?
In terms of time, there isn’t likely a difference between driving around and using just jumper cables - but it does depend on your vehicle and what you are doing in your car.
You might wonder why! You would think that driving around would produce more electricity since you have a chance to get the engine up to speed. Not quite. Most modern vehicles have a regulator built in so that the alternator doesn’t produce any more electricity while driving or idling.
In some cases, vehicles don’t have this regulator. Even then, driving your car could potentially consume more electricity by using the radio, lights, and everything on the onboard computer - which you really can’t turn off. There is a chance that just driving around normally will result in the battery level not necessarily increasing.
The effects of idling
While technically, driving around doesn’t charge your battery faster, it does help your vehicle in some ways. Simply sitting in a parking space or your driveway while running isn’t great for a vehicle or the environment. Gas powered vehicles product harmful byproducts, and excessive idling burns gas unnecessarily and shouldn’t be repeated often, as it can also lead to premature engine wear. Your vehicle is meant to travel at speed and not sit around too much.
How do I tell if my battery is OK after charging?
Some vehicles have the ability to warn you if your battery voltage is low or your battery is experiencing issues. Others vehicles will deliver this surprise on an extra cold or hot day, and simply “click” but not actually start the engine.
How to tell if battery is OK on a battery charger
First, the answer to this question does vary a bit from charger to charger. Some jump packs and chargers don’t have a way of measuring current battery life.
The tool used to measure battery voltage should either give you a green light or show an average vehicle’s voltage and amperage range of 12.4 to 12.9 volts while off and 13.7 to 14.7 while the engine is running. Lower than that you and you run the risk of having a dead battery next time.
This is also a sign that your battery is getting old - or that your alternatore isn’t running well.
Knowing if battery is charging in the vehicle
Some vehicles have either a built in warning light for your battery, or a voltmeter present on the dashboard. The volt meter can often show a range from 0 to 16 with red behind any numbers that don’t fall in the approrpriate range. This “feature” is more common on older cars and more recent trucks that use battery power for accessories often.
What should I do with the results of a battery test?
Try it again later. If you do have an issue with your alternator, your battery charge will be low again - or your vehicle will just stop running because the battery is dead.
Once you’ve charged the battery up, it will drain as you run the vehicle. If the alternator fails to continue charging, you’ve got a problem for a mechanic.
What’s the best way to charge a car battery?
Do you feel like your car battery is old enough to need a charge, or do you live in a cold or hot area where your battery might need help?
You are better off using a trickle charger to slowly charge your vehicle overnight - whether it’s in a garage or in the driveway. The best part about using a trickle charger isn’t so much that it does a better job of charging your battery. Instead, it’s very easy to plan and just setup once. Plug the trickle charger into the wall, open your hood and get in the habit of leaving the battery on the charger once in a while.
What’s the best way of charging a car battery if I live in an apartment?
Some apartments have electrical outlets on poles on spots near the front. Others might require you find a long extension cable to plug in, which is still better than hauling a battery pack or jump starter around with you and finding another vehicle to help.
Keep in mind that most home garages aren’t designed around the idea of having a battery charger plugged in for a car. Homeowners will likely need an extension cord on some level too. People who own electric cars often have to install separate hardware just to get the right amount of electricity to their car faster, so you aren’t alone at all.
What can I do to best prepare for potential battery problems?
- Buy jumper cables or a jump pack. Keep a jump pack charged
- Park your vehicle in a way that makes the front easily accessible to another car for jumper connections
- Get your vehicle serviced regularly and the battery maintained
- Replace your battery every 5 years or sooner, depending on the climate
- Be on the lookout for alternator problems
- Check your vehicle’s battery dashboard if available - they are easy to ignore
About THE AUTHOR
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding