Charging a Car Battery While It Is Still Connected

Sometimes, people prefer charging a car battery while it is still connected and completely safe. All batteries are manufactured and designed to char while connected to the vehicle during the driving process. Using a car battery while charging is essential, especially when the battery is uncharged and you wish to drive your car in case of emergencies.

Despite charging a car battery while connected being essential, it may result in electric shock while the person is driving. Also, it may result in direct current flowing within the car system, thus causing the driver’s death. The information below states how to charge a car battery while connected.

How to charge a car battery while still connectedCharging A Car Battery While It Is Still Connected

Before charging the car battery while it is connected, there are several safety tips you need to follow to avoid the occurrence of electric shock or the production of electric sparks. The guidelines include;

  1. Ground yourself using an anti-static wristband to prevent electrical problems such as electric shock and electric sparks that can affect the driver.
  2. Inspect the water level present in the car battery before charging. If the water level is low, refill the battery with only distilled water and charge the battery.
  3. Wear protective clothing to protect the whole body from any injuries. Also, wear gloves to protect the hands from any cuttings. Finally, protect your eyes by covering them with an eye protection tool.
  4. Use the correct electricity voltage that suits the car battery to avoid damaging the battery.
  5. Avoid charging the car battery in direct sunlight to avoid increasing the battery temperature and affecting the charging process.
  6. Ensure you charge your car battery while connected in a well-ventilated area to protect the battery from any form of contamination.
  7. Clean all leakages present using a clean damp cloth after the car engine cools down.
  8. Check the battery continuously during the charging process to ensure it does not over-charge.
  9. Always connect the terminals with the positive terminal matching the red cable and the black cable with the negative terminal.
  10. Before charging the battery, examine it and detect any faults, such as the presence of battery leakages. Also, replace the battery if damaged before charging it while connected.

Car battery power testing

Car battery power testing

Sometimes, the car engine fails to function hence affecting the car starting the process. Check the battery and test it to see if it has a charge or is in good condition. To detect battery faults, use the tips below to get accurate results.

  • Using a multimeter, check the status of the car battery if it is functioning as required. If the multimeter fails to record measurements, approximately 12.7v, then the battery is distorted oy has no charge.
  • Inspect the condition of the car lights and see if they are turning on and off as required. If the lights emit limited brightness, the car alternator is damaged, and the battery requires some charging.
  • Check the terminal connection of the battery and the car to see if they are functioning normally. If the terminals are dirty, remove all dirt using a recommended tool such as a hard brush. After inspecting and testing the battery’s condition, proceed to charge the battery while it is connected.

Step by step guide on how to charge a car battery while it is connected

Step by step guide on how to charge a car battery while it is connected

Despite the charging of the car battery while connected, resulting in serious damages such as electric shock, there are safe steps to charge the battery while it is still connected. The most preferred way is by using an advanced microprocessor-controller charge. The microprocessor-controller charger functions by inspecting and regulating the current flowing to the battery to keep the battery in good condition.

When charging the car battery, consider the following safety tips or steps.

Step 1: Stop the car and switch it off

Before charging the car battery, stop the car and park it in the correct position away from direct sunlight and crowded areas to protect the car battery from overheating and becoming faulty. Turn the car off and leave it for a couple of minutes until it completely cools down.

Ensure the car keys are not in ignition mode. The reason for turning off the car before charging is to prevent the occurrence of injuries and electric shock. Also, it prevents serious damage to the car parts such as the car engine and the battery, among others.

Step 2: Connect the car battery to the power source

Before connecting the battery to the charger, inspect the condition of the wires and ensure they are functioning correctly. If worn out, consider replacing them before proceeding to the next step. Connect the red terminal to the positive terminal and the black wire to the negative terminal. Incorrect matching of the cable may blow out the wires, even the entire car battery.

First, connect the battery to the battery charger. Ensure the terminals are firmly tightened but not overtightened to get accurate results without bending or damaging the wires. Also, it is advisable to use the correct wires if the wires are blown out, but if you cannot connect the battery to the charger due to fear of the occurrence of electric shock, seek help from a nearby service center.

Step 3: Connect the battery charger to the power supply switch

After ensuring the car battery and the charge are connected well, connect the switch to the power supply switch and switch it on. Before connecting the charger to the power source, inspect the switch’s condition and ensure it is functioning correctly. If the switch is faulty, consider using another switch or port. Ensure you use the correct power voltage recommended by the manufacturer. Check the charging connection to see if the battery is charging correctly.

Step 4: Leave the battery to charge fully

While driving, leave the battery to charge fully for a couple of hours, depending on the recommended time stated by the manufacturer. When the battery is charging, avoid disconnecting and connecting the battery as this damages the battery or the charger.

Step 5: Switch off the power switch

After the battery is fully charged, disconnect the battery and the charger terminals to prevent overcharging of the car battery. If you fail to disconnect the terminals, electric sparks are produced and light any hydrogen gas present resulting in the ignition of the battery and the whole vehicle. Therefore, it is advisable to switch off the power switch immediately after the battery is full.

Also, when plugging the charger and battery terminals, observe the order of sequence to avoid blowing the wires. For instance, disconnect the black wire first, followed by the red wire. If you have a battery maintainer, you may consider leaving it connected until you decide to switch it off.

Reasons why car batteries fail to charge while it is connected

There are several reasons why the car battery may fail to charge, and they are as follows.

  1. Dead car battery prevents transmission of charge from the power source to the battery.
  2. A fault battery charger that fails to transmit power from the power source.
  3. Damaged power switch, etc.


Finding that the car battery is uncharged, especially during emergencies, can be stressful. Luckily the article shows the best ways of charging the car battery while it is connected. Follow the steps carefully to avoid damaging the car battery.

Finally, follow the safety tips above before charging the car battery, such as grounding yourself using an anti-static wristband to protect yourself from electric shock. Also, ensure you maintain the car and the car battery to improve its performance and prolong its lifespan.

How to Charge Your Car Battery. Part of the series: Car Maintenance Tips. Make sure when charging a car battery to identify the positive and negative posts before placing charging clamps on. Charge an auto battery with tips from an automotive service excellence (ASE)-certified master auto technician in this free video on automotive maintenance.

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