How To Charge a Car Battery

How to charge a car battery
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A car battery is a key component in any vehicle. It needs to be in perfect shape to start your car, especially in winter conditions. 

If you don’t take good care of it, you might find yourself on the side of the road in the dead of winter with a dead battery sooner than you might think. By simply charging your car battery every now and then or connecting it to a trickle charger routinely, your battery will always be topped up, reliable and ready to go. It will live much longer too.

In this article, we’ll explain 5 different methods you can use to charge a car battery, depending on your circumstances and needs. 

Different Car Battery Charging Methods

1. With a Trickle Charger

A trickle charger is a low-amperage charger that keeps your car battery topped up. It is made for preventative maintenance purposes mainly. A trickle charger is your car battery’s best friend. 

An electronic trickle charger is designed to prolong the life of your car battery by intelligently “training” your battery for optimal performance.

By continuously diagnosing and evaluating your battery’s condition and by running a bespoke cycle of pulses and charges/discharges, your car battery will remain fully charged, it will perform better and live longer.

A trickle charger needs to be plugged into a mains power outlet. Because it is low-amp, it is generally not your best option to charge a completely drained battery because it would take up to several days depending on your battery amperage and the state it is in. 

2. With a Fast Charger

A fast charger is a high-amperage mains-powered car battery charger that is capable of completely charging a dead car battery in under an hour depending on the battery type, amperage and the state it is in. Most have a low-amp setting for maintenance charging too. Some have a boost-setting that even enables instant jump-starting. 

However, depending on the amperage and technology used, fast-charging is the most aggressive way to charge a drained battery. It can result in battery performance loss and shortened battery life. That’s why fast charging should only be used as a last option.

3. With a Portable Jump Starter 

A portable jump starter is a small lithium battery powered device that can deliver a high-amperage boost to start a car with a drained battery. The boost passes through the car battery to start the engine but doesn’t charge it. It’s your car engine’s alternator that will start charging your car battery. Once you’ve started your car, you’ll need to drive your car or let it idle to charge your car battery.

4. By Jump-Starting With Another Car

By connecting your drained battery to the battery of another car with a running engine, you should be able to start your engine. In turn, your engine’s alternator will charge your car battery. Once you’ve started your car, you’ll need to drive your car or let it idle to charge your car battery.

5. By Push-Starting

If your car is equipped with a manual gearbox, you can push-start it. When the engine starts, the alternator will charge your car battery. Once you’ve started your car, you’ll need to drive your car or let it idle to charge your car battery.

If your car has an automatic gearbox, it can NOT be push-started.

Here is a step-by-step guide for charging a car battery using the different methods:

1. With a Trickle Charger

Everything you need to charge your battery with a trickle charger:

 

  1. Locate your car’s battery and check what type of battery it is (lead-acid / AGM / EFB…). Consult your car owners manual when in doubt.
  2. Plug the trickle-charger’s power cord into an outlet and turn it on (some are always on and have no on/off switch). Make sure that the trickle charger is set to 12V (some pre-1960s classic cars may require 6V) and select the right type of battery (lead-acid / AGM / EFB…).
  3. Connect the trickle-charger’s alligator clamps to the car battery terminals:
    red (+) on red (+), black (-) on black (-).
  4. Double check the trickle-charger’s settings and make sure there are no fault indications. Consult your trickle-charger’s manual when in doubt.
  5. The trickle-charger displays the charging status and will switch to maintenance regime when fully charged. Depending on the charger, battery amperage and the state the battery is in, charging a completely drained car battery can take up to 48 hours

If your car battery won’t charge or is dead again within days, you might want to replace it. Check out our Best Car Batteries. To test your battery’s condition, take a look at our Best Car Battery Testers.

2. With a Fast Charger

Everything you need to charge your car battery with a fast charger:

 

  1. Locate your car’s battery and check what type of battery it is (lead-acid / AGM / EFB…). Consult your car owners manual when in doubt.
  2. Plug the fast charger’s power cord into an outlet and turn it on (some are always on and have no on/off switch). Make sure that the fast charger is set to 12V (some pre-1960s classic cars may require 6V) and select the right type of battery (lead-acid / AGM / EFB…).
  3. Connect the fast charger’s alligator clamps to the car battery terminals:
    red (+) on red (+), black (-) on black (-).
  4. Double check the fast charger’s settings and make sure there are no fault indications. Consult your fast charger’s manual when in doubt.
  5. The fast charger displays the charging status and will switch to maintenance regime when fully charged. Depending on the charger, battery amperage and the state the battery is in, charging a completely drained car battery can take up to one hour. Some have a boost-setting that even enables instant jump-starting. 

If your car battery won’t charge or is dead again within days, you might want to replace it. Check out our Best Car Batteries. To test your battery’s condition, take a look at our Best Car Battery Testers.

3. With a Portable Jump Starter 

Everything you need to charge your car battery with a portable jump starter:

 

  1. Locate your car’s battery. Consult your car owners manual when in doubt.
  2. Connect the portable jump starter’s alligator clamps to the car battery terminals:
    red (+) on red (+), black (-) on black (-).
  3. Double check the portable jump starter’s settings and make sure there are no fault indications. Consult your portable jump starter’s manual when in doubt.
  4. Start your car.
  5. With the engine running, remove the portable jump starter but stay clear of any moving parts like the fan blades, pulleys and belts to avoid serious injury. Do not turn the engine off before the alternator has had time to recharge your battery.
  6. Depending on your type of battery and alternator and the state they are in, it will take about 30 minutes of continuous daylight driving with all electronic accessories turned off to recharge your car battery to an acceptable level. At night with the lights turned on, it may take up to an hour of continuous driving. If you let your car idle to charge the battery, it may take up to 2 hours.

If your car battery won’t charge or is dead again within days, you might want to replace it. Check out our Best Car Batteries. To test your battery’s condition, take a look at our Best Car Battery Testers.

4. By Jump-Starting With Another Car

Check out our comprehensive guide on How To Jump-Start a Car.

5. By Push-Starting (manual gearbox only)

Everything you need to charge your car battery by push-starting:

 

  • one or two helpful people to push your car

     

  1. Switch your ignition key to the “ON” position.
  2. Put your gearbox in second gear and keep your clutch pedal pushed all the way to the floor. Stay in the driver’s seat with your hands and feet in normal driving position.
  3. On level terrain, have two strong people push your car as hard as they can when traffic allows. On a strong slope with your car facing downhill, it may be possible to release your handbrake when traffic allows and let gravity do the work without involving other people. Always use caution and common sense and be aware of your surroundings!
  4. When your car has reached walking speed, abruptly release your clutch pedal and your engine should start. Be careful not to stall it because you’ll have to do it all over again. Remember: your battery isn’t charged yet! Do not turn the engine off before the alternator has had time to recharge your battery.
  5. Depending on your type of battery and alternator and the state they are in, it will take about 30 minutes of continuous daylight driving with all electronic accessories turned off to recharge your car battery to an acceptable level. At night with the lights turned on, it may take up to an hour of continuous driving. If you let your car idle to charge the battery, it may take up to 2 hours.

If your car battery won’t charge or is dead again within days, you might want to replace it. Check out our Best Car Batteries. To test your battery’s condition, take a look at our Best Car Battery Testers.

FAQ’s

How Do You Charge a Car Battery Without a Charger?

If you are still able to start your car, you can charge a car battery without a charger by simply driving your car or by letting it idle. 

Depending on your type of battery and alternator and the state they are in, it will take about 30 minutes of continuous daylight driving with all electronic accessories turned off to recharge your car battery to an acceptable level. At night with the lights turned on, it may take up to an hour of continuous driving. If you let your car idle to charge the battery, it may take up to 2 hours.

If your battery is too weak to start your engine, you can jump-start or push-start your car and let the alternator charge your battery by letting your engine idle or by driving your car. 

How Do You Charge a Dead Car Battery?

You can charge a dead car battery using a trickle charger or a fast charger. If you don’t have a charger, you can charge a dead car battery by jump-starting or push-starting your car and driving it for at least 30 minutes continuously with all lights and electronic accessories turned off. Your alternator should have had time to recharge it to an acceptable level by then.

How Much is a Car Battery Charger?

A good car battery charger doesn’t have to be expensive. However, prices vary widely depending on the type of charger. Check out our comprehensive guide on the Best Car Battery Chargers.

What Can Go Wrong when Charging a Car Battery?

Nothing can go wrong if you use a quality car battery charger. It is 100% safe to use because it has multiple safety features built in. They are not as expensive as you’d expect either. 

You don’t want  to buy a cheap one and run the risk of overcharging, sparks, electrocution, explosions, fire or damage to your car’s electrical components. That cheap charger could turn out to be very expensive.

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