How to Recharge a Car Battery?

While recharging a dead car battery is a straightforward job, if you’re not confident, call a mechanic to do it for you. Here’s how they’ll recharge it:

1. Use a Jumper Cable 

They’ll jump-start the car using a jump starter or a jumper cable and a healthy battery from another vehicle (or a portable car battery pack). Then, they’ll recharge your battery by driving around. 

They’ll keep the engine running for at least 30 minutes to allow the alternator to recharge the battery.

2. Use a Car Battery Charger

They’ll test the battery voltage and check the positive terminal and the negative terminal for corrosion. 

Note: Depending on the battery chemistry, a lead acid battery, NiMH battery (nickel-metal hydride), or lithium-ion battery (li-ion) may have a distinct battery charge current or constant voltage specification. They’ll check the manufacturer’s manual for the best way to recharge the battery.

Next, they’ll hook up the rechargeable battery to a charger with a charging cable. They may charge while the battery is in the car or disconnected and removed. 

Remember, maintaining necessary safety precautions while using a car battery charger is critical to safety.

When Do You Need A Battery Recharge?

Here are a few signs indicating it’s time to recharge your car battery:

1. Dead Battery

If the car doesn’t start, your battery may be dead and needs recharging. A dead battery indicates that its battery voltage is below its functional battery capacity. 

For a car, the battery charge voltage is around 12.6 volts — that’s about 8 AAA batteries (the battery type used in flashlights), which add up to 12 V (1.5 V x 8).

Rechargeable batteries can die when:

• The headlights are left on for too long
• The battery has a charging system failure
• A battery terminal is corroded with sulfuric acid
• The car has been inactive for quite some time
• It loses power because of cold weather conditions

Note: If your car battery dies frequently, you may need a battery replacement.

2. Broken Alternator

Alternators are responsible for replenishing the battery power while the car is running. So, if you have a broken alternator, your vehicle won’t be able to recharge the battery automatically.

In this case, your car battery will need a manual recharge. But getting the alternator fixed should be your priority. A broken alternator can overcharge the battery and reduce its lifespan.

3. Check Engine Light Flashing

Sometimes, a lit check engine warning light can mean you need to recharge your battery. 

What should you do?
You could drive around to replenish battery power If you don’t notice any performance loss (or other symptoms like strange noises).

But if the dashboard light doesn’t switch off, pull over safely and call a mechanic for help. 

A professional mechanic will test the rechargeable battery and run diagnostics to identify the root issue behind the warning light.

4. The Car Hasn’t Been Driven for Long

Rechargeable batteries can drain if the car has been inactive for a long time. Most healthy car batteries can last at least two weeks without use but will discharge beyond that.

If the car doesn’t start due to inactivity, you’ll need professional help to check for corrosion or other energy storage issues.

Note: A lead acid battery has a faster self–discharge rate than an AGM (type of gel battery) or lithium-ion battery. So, it’ll drain faster when not in use.

5. Electrical Issues

Electrical malfunctions indicate battery problems. They can happen even when the car starts and runs fine.

So, if your car’s air conditioning suddenly turns off or the headlights and interior lights go dim, your battery may need recharging.

How Urgent Is A Battery Recharge?

The battery provides the car with power to start. Your car won’t turn on if the battery is dead. That’s why it’s best to charge the battery ASAP if you need to use the car in an emergency.

You should also get a battery test to see if any other issues could harm the charging cycle and battery lifespan.

How Much Does It Cost To Charge A Car Battery?

An auto repair shop may charge between $50-$60. 

But if the battery is faulty, you’ll need to buy a new one to replace it. Generally, a repair shop may charge a half hour to one hour of labor to install a common automotive battery (standard lead acid rechargeable batteries).

4 FAQs On Battery Recharge

Here are three frequent queries about the charging process of automotive batteries:

1. What Is a Battery Recharge?

A battery recharge is the replenishment of a discharged battery with electrical energy.

For cars, this isn’t as simple as charging rechargeable AA batteries or an AAA battery with a charger.

How does this happen for a car?
Typically, the alternator recharges the battery while the car is running. It turns mechanical energy from the car’s crankshaft into electrical energy to charge the battery.

But an alternator can’t recharge a battery without a running car. So, if the vehicle can’t start, you’ll need to find alternative solutions, like a charger or portable car battery pack, to get the battery recharged.

2. Can I Recharge a Dead Battery?

Yes, recharging a dead car battery is possible — provided it’s only discharged and doesn’t have other issues like battery swelling or leaking. 

Although you can do it yourself, it is always best to seek professional assistance for optimized battery charging and to fix any recharging issues. 

If your battery is still under warranty, you may consider replacing it. 

Note: Regular battery service will help avoid a dead car battery in the long run.

3. How Long Does it Take to Charge a Dead Battery?

A flat car battery can take around 10 to 24 hours for a full battery charge. But this battery charging time depends on the battery type and charging mode. 

Here are a few estimates for the charging process based on the battery chemistry:

• Lead acid batteries have an average charging time of 12 to 16 hours. A flooded lead acid battery charges five times slower than an AGM battery (gel battery).

• While a lithium battery takes between 30 minutes to 4.5 hours for a full recharge, a NiMH battery takes up to 15 hours.

• It can take up to 48 hours to trickle charge and replenish a car’s battery capacity using a trickle charger. The charging time depends on the type of trickle charger. 

Trickle charge is preferred for optimized battery charging. It helps maintain your battery performance and prevent potential battery issues. Fast charging (using a fast charger) may harm your car battery’s energy storage in the long run. 

So, it’s best to slowly recharge batteries using constant current (constant voltage) or a smart battery charger to preserve battery life. Also, regular battery service is imperative for your car battery’s longevity.