A Step-By-Step Guide on How to Charge a Car Battery

a person working on a car engine
How to Charge a Car Battery Gannon Burgett - Car and Driver

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Car batteries are like avocados: they always seem to go bad at the worst possible times. So, what do you do if your car's battery runs out of juice? Well, you could use a portable jump starter or, worst case, finagle a jump-start from a neighbor, friend, or relative to get some energy back into it (try doing that with an avocado). But there's another important step to take even after that: give your battery a recharge.

This is especially important if you don't plan to regularly drive your car after jumping it. Say you're putting it away for the winter or planning to go on a long vacation in the next day or two.

Where do you get a battery charger, though? Well, most auto parts stores carry them, and they're readily available through online retailers such as Amazon.

Once you have the charger in hand, you'll want to put it to work ASAP. Fortunately doing so is super easy. Read on to see how to use a battery charger to recharge or maintain the charge of your car's battery in five simple steps—with accompanying video clips, no less!

A word of caution—if a battery charger fails to recharge your car's battery, then there are likely larger issues at play, such as a bad battery, parasitic draw, or other electrical issues. If this happens, your best bet is to jump-start the vehicle and take it down to your trusty local mechanic for a proper diagnosis.

What to Expect

  • Estimated time: About 5 minutes for setup, 1–6 hours for battery charging, overnight for a full recharge.

  • Experience level: Beginner.

  • If you can't find the battery terminals under the hood, then check the owner's manual—it will save you a lot of time.

What You'll Need

Along with a battery charger, there are a few things you might need when tackling this job. These ought to do the trick.

How to Recharge Your Car Battery: Step-By-Step

Step 1: Find your vehicle's battery and locate the positive and negative terminals.

Most cars have their battery under the hood. The positive terminal is marked with a "+," and the negative terminal is marked with a "-." Sometimes the terminals are protected by plastic covers that need to be flipped out of the way. Other vehicles have their batteries in the trunk. In these instances, you'll often find a positive terminal to connect to. Use the car's under hood sheetmetal as the negative terminal. If you're struggling to find the battery and/or it's associated terminals, consult that handy owner's manual.

Step 2: Verify your battery charger is unplugged and turned off.

Before attaching the battery charger, it's important to verify no current is flowing through the charger before connecting it to the terminals on your vehicle. Unplugging the charger prevents sparks—which can be dangerous if your battery is leaking. Read the instructions that come with the battery charger, as each charger operates a little differently.

Step 3: Attach the battery charger to your vehicle's battery terminals.

Always start by attaching the charger's red clamp to the battery's positive terminal and then attaching the black clamp to the negative terminal. Give the clamps a little wiggle to ensure that they have a good connection to the terminals. For the greatest safety, keep the charger as far away from the battery as the cables allow.

Step 4: Plug the charger in and turn it on.

Some chargers identify the battery automatically once connected. Others need this information inputted manually. Once that's figured out, simply select the charging amperage you want. As a rule of thumb, higher amperage equals faster charge times, while lower amperage is slower. The reason to go the latter route is that it's more gentle on your vehicle's battery, which ought to extend its life.

Some chargers shut off automatically once the job is complete. Others don't, and may instead have gauges that let you know the battery's state of charge and/or when it's fully charged. Many battery chargers deliver two to six amps of current. At these rates, it can take several hours (or more) to recharge a dead car battery. Be sure to double-check the instructions that come with the charger to ensure you're operating it correctly.

Step 5: Disconnect everything once the battery is charged.

When the battery is fully charged, shut off the charger and unplug it. Then remove the cables, unhooking the negative (black) clamp first.

Our Recommended Car Battery Chargers

NOCO Genius 1

The NOCO Genius 1 employs a lower 1.0-amp setting to begin a slow, steady charge. It's designed to work with the gamut of battery options—regular lead-acid, AGM, and lithium. Navigating the mode selection button provided a satisfying tactile feel when cycling through options. NOCO seems focused on delivering an effective, user-friendly charger, and to that end, the company nailed it with the Genius 1.

<p><a href="https://www.amazon.com/dp/B07W46BX31?tag=syn-yahoo-20&ascsubtag=%5Bartid%7C10048.a.26862050%5Bsrc%7Cyahoo-us" rel="nofollow noopener" target="_blank" data-ylk="slk:Shop Now;elm:context_link;itc:0;sec:content-canvas" class="link ">Shop Now</a></p><p>NOCO Genius 1</p><p>amazon.com</p><p>$29.95</p><span class="copyright">Gannon Burgett</span>

Battery Tender 3-Amp Battery Charger

For Battery Tender's 3.0-amp model, we struggled to find any flaws other than some users may find the LED lights a little dim. Otherwise, in terms of its operation, the Battery Tender uses a single button to toggle between 6- and 12-volt. Once a selection is made, you set it and forget it. It's that straightforward. We commend Battery Tender for adhering to the essentials, especially in a market where products can become overly complex.

<p><a href="https://www.amazon.com/dp/B016S7NHWQ?tag=syn-yahoo-20&ascsubtag=%5Bartid%7C10048.a.26862050%5Bsrc%7Cyahoo-us" rel="nofollow noopener" target="_blank" data-ylk="slk:Shop Now;elm:context_link;itc:0;sec:content-canvas" class="link ">Shop Now</a></p><p>Battery Tender 3-Amp Battery Charger</p><p>amazon.com</p><p>$69.95</p><span class="copyright">Gannon Burgett</span>

Sun Energise Solar Battery Charger & Maintainer

If your vehicle will be parked away from a conventional power source, consider harnessing the sun instead with the Sun Energise 10-watt solar panel. Designed to be used inside or outside your car, the Sun Energise features four suction cups for windshield application. Naturally, the prime limitation of Sun Energise is its reliance on sunlight. Because of this, we recommend using it as a reliable backup rather than your sole charging provider.

<p><a href="https://www.amazon.com/dp/B09C2FYZGW?tag=syn-yahoo-20&ascsubtag=%5Bartid%7C10048.a.26862050%5Bsrc%7Cyahoo-us" rel="nofollow noopener" target="_blank" data-ylk="slk:Shop Now;elm:context_link;itc:0;sec:content-canvas" class="link ">Shop Now</a></p><p>Sun Energise Solar Battery Charger & Maintainer</p><p>amazon.com</p><p>$55.95</p><span class="copyright">Gannon Burgett</span>


How long does it take to charge a car battery?

This really depends on the amount of amperage the battery charger outputs. On the low end, most range from one to three amps (often called a trickle charge) and top out between eight to twelve amps. Other battery chargers output higher amperage, but that amount can overwhelm your vehicle's battery and negatively impact its longevity.

A trickle charge typically recharges a depleted (or near-depleted) car battery overnight. Such low amperage is usually used for maintaining the battery (such as when storing your car away for winter), but it can also be used to recharge the battery if you can spare the additional time it takes. Higher output amperage will usually charge your vehicle's battery in anywhere from one to six hours, depending on the state of charge.

How long does it take to charge a dead car battery?

Expect to let the charger take its sweet time with this. For a completely dead battery, your best bet is to let it charge overnight at low amperage to prevent any additional stress to the battery's cells. You can rush it, but the risk of causing long-term damage to the battery is much higher.

How do I charge a battery at home?

All you need is a battery charger and an outlet. Locate your vehicle's battery terminals, verify your charger is unplugged and off, attach the charger to the battery, plug it in and turn it on, set the correct settings, and you're good to go!

How do I charge a car battery without a charger?

Ideally, your gas- or diesel-powered vehicle is supposed to do this on its own thanks to a handy part called an alternator. Simply put, the alternator is a magnetic coil that is powered by the vehicle's engine. It then generates current that gets routed back to the battery, recharging it as you drive. A faulty alternator is often the cause of a dead battery. In short, your battery always needs a charger of sorts to maintain a charge. It's a job the alternator does if everything's working right.

How to Tell If a Car Battery Is Dead

The terminology can be confusing, but a "dead" battery is typically just a battery with a low charge. Thanks to the robust engineering that goes into these magic boxes, a simple recharge might be all it needs. But how can you tell?

Now, there are a multitude of reasons your car won't start—but a dead battery is a good place to begin troubleshooting. If you hear a "tick-tick-tick"or your engine "chugs" slowly while attempting to start, then you may have a low battery. Most vehicles will even illuminate a red battery light within the instrument panel to warn you that there's an issue with the charging system.

If you jump-start a car and it starts, that's great. But it's important to figure out why you needed to jump-start it in the first place. Connecting the battery to a charger afterward is a good next step. From here, you can see if your battery takes or holds a charge. This can lead you to the next diagnostic phase, such as testing the alternator or checking for parasitic draw.

Another option is to swing by your trusty local mechanic for a battery test. This can give you an idea of the battery's condition and if you need to replace the battery. Remember, there's nothing wrong with having a professional check it out—it might cost more upfront, but it can save you from chasing around an electrical gremlin on a late Saturday night.

In the end, if your car doesn't start normally on its own, something is wrong. Just because it started when you jumped it, doesn't erase the fact that it needed to be jump-started. It's worth figuring out the problem—whether that be a low battery or something else—so you don't have to deal with it again.

Collin Morgan contributed to this story.

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