How Far Do I Need to Drive to Charge My Car Battery?
- by Joe Weber - updated on 4/3/2024
Every night when you get home from work, you park the car in the driveway (or in the garage if you're lucky) and head inside. The next morning you jump in and turn the key, and the car starts like a champ. How does your car battery stay charged even though you just drove it home and let it sit? It's not magic, I promise. It's beautiful engineering.
What Makes Car Batteries Different?
Car batteries provide the massive jolt of electricity needed to start your vehicle's engine. At the turn of the key, a signal is sent to the battery to send a massive amount of energy to the vehicle's starter to spin the heavy flywheel to spin the crankshaft to begin the starting process. If all works as expected, your engine will start within seconds and you can go about your drive.
Once that's accomplished, your vehicle's alternator takes over the task of keeping the battery charged while you drive. One thing many people fail to realize is that recharging a car battery takes time. If you don't drive your vehicle long enough or often enough, your battery's charge will continue to get lower and lower each time you start the engine. Leading to the dreaded dead battery at the worst time. So, how long do you need to drive your car to recharge the battery? Does your driving speed affect how fast your battery recharges? Find out below.
How Many Volts Are in a Fully Charged Car Battery?
But first, let's learn a little about car batteries. Most modern vehicles have a 12-volt battery underneath the hood. A 12-volt car battery contains six individual cells, each of which will contain 2.1 volts of power when fully charged. So, in a perfect world, when the engine is off, a car battery is considered fully charged at 12.4 to 12.6 volts.
When your battery's voltage drops even a small amount it can make a big difference in its overall performance. For instance, a voltage of 12.1 volts means your battery is operating at only 50% of its total charge. Once it drops down to 11.6 volts, the battery is almost completely discharged, the dreaded dead battery. For more information on how car batteries operate, see "How Does a Car Battery Work?"
How Much Do I Need to Drive to Fully Charge a Battery?
The beauty of a car battery is that it will charge while you are out running errands, with a few caveats. To avoid having to plug your car battery into a charger at home, you need a minimum of 1000 revolutions per minute (RPM) from your engine to generate the power needed to charge your battery. Faster speeds generate more RPMs, so your battery will recharge faster at speeds of 55 MPH or higher.
It takes most vehicles about 30 minutes of driving at highway speeds to fully recharge the battery. Keep in mind that 30 minutes is an average. If your battery is severely discharged, recharging it may take even longer.
Do Car Batteries Charge While Idling?
While not ideal, a car with an idling engine will still recharge your battery, but at a much lower rate than if you were driving. The reason for this is that modern cars have a lot of additional electronics that use up power. Guess which component is responsible for generating the power for these additional systems. That's right, it's your alternator.
When you get your car started and just let it sit idle, the engine isn't working very hard and not rotating as fast as it would if you were driving, operating at lower RPMs, meaning it will take your battery much longer to recharge. How long? We're talking several hours if your battery was dead. Your best bet is to just take your car for a spin instead of leaving it idling in your driveway.
How Long Does a Car Battery Last Without Being Used?
Leaving your car sit unused for a short time doesn't mean the end of your battery. However, if you let it sit for a longer period, you could be asking for trouble. An idle battery can go from fully charged to completely dead in a little under two months. Your battery will die even faster if it's older than three years or wasn't fully charged the last time you drove it.
One thing that's not good for your battery is taking a lot of short driving trips in a row. There's nothing wrong with tackling a bunch of errands, but if you're constantly starting and stopping your engine with only a few minutes of driving in between, it will drain your battery pretty quickly and not be allowed to recharge. Try to take a 30-minute drive on the highway at least once a week to give your alternator the time it needs to fully recharge your battery. Find more tips on how to keep a car battery from dying when not in use.
What are the Different Types of Battery Chargers?
So what do you do if you have a car that you don't typically drive all that often? Your best bet is to pick up a battery charger that you can connect when you aren't using the vehicle. A battery charger will help keep your battery charged up and healthy so that it's ready to go. When shopping for a battery charger, you'll want to follow two basic rules.
Rule number one
The charger you select must be compatible with your battery's chemistry. So what do we mean by chemistry? For a lead acid battery, you'll need to find a lead acid charger. If you have an AGM battery in your vehicle, you'll need a charger that is AGM compatible. Many modern battery chargers have different settings that enable them to charge batteries with different chemistries.
Rule number two
The voltage of your charger must match the output voltage of your battery. Most cars and trucks use a 12-volt battery so you will need to get your hands on a 12-volt charger. In the rare event that you have a truck that uses a 24-volt battery, be sure that you get a 24-volt charger. You must follow both of these rules. Charging a battery with the wrong charger can permanently damage your vehicle's battery.
Bonus tip
There are three different types of battery chargers: standard chargers, trickle chargers and battery maintainers, each of which works a bit differently. Learn the difference between these three types of chargers in our blog entitled, "When Should You Use a Battery Maintainer?"
How Do You Know When Your Battery Needs to Be Replaced?
No matter how well you care for your battery, eventually, it will have to be replaced. Car batteries typically last between three and five years. Several symptoms will help tell you when your battery is dying. Aging car batteries often have a hard time holding a charge, so if your battery struggles to start up your engine, even after long drives, that's a good sign it might be going. If you find yourself having to jump-start your engine regularly, that's another good sign that your battery needs to be replaced.
Have Your Battery Tested for Free at Batteries Plus
Are you starting to see some of the telltale signs that your battery is going bad and are not sure if your battery still has life in it? Drive over to your nearest Batteries Plus for a free test. We'll test your battery's Cold Cranking Amps and voltage, as well as your vehicle's starter and alternator to make sure there aren't any underlying issues that can affect your battery.
If you need a new battery, we have plenty of replacement car batteries available from brands you know and trust like Duracell Ultra, Optima and our own premium brand X2Power. Plus, we offer expert installation on most makes and models at most of our locations. (fees may vary from location to location and the difficulty of the installation)
Looking for more car battery troubleshooting tips? Our blog entitled "6 Reasons Your Car Battery Isn't Working" has plenty of useful information to help you out.