How to charge a car battery? – practical tips and tricks

29 Jul 2023

A car battery is an extremely important component of a vehicle that provides the necessary energy to start the engine and power electronics. Nevertheless, batteries can run down due to various factors, such as prolonged car stops or accidents involving forgetting the lights. In such situations, it becomes necessary to charge the battery to restore it to full power. In this article, we will provide information on how to properly charge a car battery to ensure its long life.

Car repairman wearing a white uniform standing and holding a wrench that is an essential tool for a mechanic

How long do you charge the battery?

The charging time of a battery depends on several factors, such as how far the battery is discharged, its capacity and also the power of the charger. In general, it takes about 4-12 hours to charge a car battery.

How to connect the charger to the battery?

Connecting the charger to the battery requires caution to avoid possible damage. Follow the steps below:

  • Make sure the car engine is turned off.
  • Open the hood of the car and locate the battery.
  • Identify the battery clamps: the positive (+) usually marked in red, and the negative (-) in black.
  • Connect the red terminal of the charger to the positive (+) terminal of the battery, and the black terminal to the negative (-) terminal.
  • Ensure that the connections are secure and there is no play.
  • Connect the rectifier to a power source.
  • Start the charger according to the manufacturer’s instructions.

Charging the battery with an alternator

In some situations, you can use car battery charging through a car that is already on. In order to properly perform this operation, you need to:

  • Connect the red end of the wire to the positive (+) terminal of the battery and the black end to the negative (-) terminal.
  • Ensure that the connections are secure and there is no play.
  • Start the engine of a vehicle that has a full battery connected.
  • Leave the car running for a few minutes so that the running engine will recharge the weaker battery
  • Then turn off the engine and disconnect the wires starting with the black end and then the red end.
  • Start the car and then go on a long trip during which the alternator will be able to charge the battery.


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