How to Charge a Car Battery?

Charging a car battery can take 4-8 hours with a 12-volt battery charger. You can recharge your car battery at home, parked in a well-ventilated garage. Charging a battery can take most of the day or all night.

Even so, it’s a good idea to recharge your car battery every so often if it sits parked for a few days between drives. Parasitic draw, as in the amps your car’s electronics pulls from the battery when the engine is off, can drain a battery faster than you think.

Charging the battery will keep your car’s electronics responsive and reliable. On the other hand, discharged car batteries can become permanently damaged in just a few hours.

Let’s go through the essentials, including the steps to charge a battery, how many volts your battery should have. Let’s get started.

What Does a Car Battery Do?

The first purpose of an car battery is to provide power for starting your vehicle. It also acts as a surge protector for the car’s computer and provides power for short-term use of things like lights, stereo, GPS or wipers when the engine is off.

The car battery is part of the starting system. There are three main components in this system:

1. The ignition switch is either the starter button you press or where you insert your key.
2. The switch controls the starter relay (also called a solenoid). When you turn the ignition, it sends a small electrical current to the starter relay. This causes a pair of contacts to close.
3. When those contacts close, the battery sends voltage to the starter motor, which turns some gears to start the car.

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 sheet metal 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 gentler 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.

How long does it take to charge a car battery?

If the battery voltage is below 11.85 and your charger is putting out a 5-amp charge rate, it will take about 12 hours to fully charge a battery with 400 to 500 cold-cranking amps. The same battery will take about 6 hours to fully charge if the charge rate is 10 amps.

The lower the open-circuit voltage in the battery and the more cold-cranking amps, the longer it will take to charge the battery.

If a cell is bad, the battery won’t hold a charge. In this case, bring your battery or your vehicle with your battery to a local Car Care Center and they will change your vehicle’s battery.

Charge or Replace?

The lifespan of a car battery can depend on several factors, from the type of battery to your driving habits to the climate and conditions where you live. However, replacing a poorly functioning battery isn’t always necessary.

If your battery is less than three years old, charging it could prolong its life and save you money. Often, all a battery needs is a slight recharge to return to optimal performance.

When to Charge a Battery

• After sitting for an extended period. Batteries lose charge over time, even when not in use. If your car has been sitting unused for months, your battery is likely in need of a charge.
• Cold weather exposure. Cold weather diminishes battery capacity. If your car sits in frigid temps, it may require charging.
• Parasitic draw or user error. If you left the lights on in your car, or your battery is drawing more power while the car is off (parasitic draw) due to an abundance of electronics onboard, a charge can bring it back to full capacity.

When to Replace a Car Battery

• Old age. A conventional lead-acid car battery has a lifespan of three to five years. If yours is reaching the upper limit and dies suddenly, it may be time to replace it.
• Frequent dying. If your battery dies often, even after being fully charged, it will likely need to be replaced.
• Visible damage. If you pop the hood and see cracks, bulges or other visible signs of damage, do not attempt to recharge your battery. Take it to a qualified technician and replace the damaged battery.
• It smells bad. Batteries don’t typically have a scent, but when a car battery is damaged or dying, it may be releasing hydrogen sulfide gas or leaking sulfuric acid from inside the battery. Since gas and sulfuric acid are toxic, immediate, professional attention is required.
• Chronic electrical issues. If you notice persistent electrical issues like dimming lights, slow cranking or malfunctioning electrical components, your battery may be failing.

FAQs.