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Charging the Low-Voltage Battery of Your EV: A Step-by-Step Guide

Sep 13,2023 | TCcharger

Electric vehicles (EVs) are known for their high-voltage battery packs that power the electric motor, but they also have a low-voltage battery that plays a crucial role in running various vehicle systems. Just like conventional vehicles, these low-voltage batteries can sometimes require charging or jump-starting when they become depleted. In this blog post, we'll provide a step-by-step guide on how to charge the low-voltage battery of your EV.

  1. Safety First

Before attempting to charge the low-voltage battery of your EV, prioritize safety. Ensure that the vehicle is parked in a safe location, away from traffic, and on a level surface. Make sure the parking brake is engaged, and the vehicle is turned off. Additionally, always wear appropriate safety gear, including gloves and safety glasses, when working with batteries.

  1. Locate the Low-Voltage Battery

The low-voltage battery in an EV is usually a small 12-volt battery, similar to the battery in a traditional gasoline-powered car. It is typically located in the front of the vehicle, often under the hood or in the trunk. Consult your vehicle's manual or contact the manufacturer to determine the precise location.

  1. Gather the Necessary Equipment

To charge the low-voltage battery, you'll need the following equipment:

  • A 12-volt battery charger: Ensure it is compatible with lead-acid batteries, which are commonly used in low-voltage systems.
  • Safety gear: Gloves and safety glasses.
  • A well-ventilated workspace.
  1. Connect the Charger

Follow these steps to connect the charger to the low-voltage battery:

a. Open the hood or access the battery compartment as needed. b. Locate the positive (+) and negative (-) terminals on the low-voltage battery. c. Connect the red (positive) clamp from the battery charger to the positive terminal of the battery. d. Connect the black (negative) clamp from the battery charger to the negative terminal of the battery.

  1. Set the Charger

Configure the battery charger settings as follows:

  • Select the appropriate voltage setting (12 volts).
  • Choose the charging rate according to the manufacturer's recommendations. A slow or trickle charge is usually sufficient for low-voltage batteries.
  • If your charger has a timer, set it to charge for the recommended time (typically a few hours).
  1. Start Charging

After configuring the charger settings, plug it into a power source and turn it on. The charger will begin replenishing the low-voltage battery.

  1. Monitor the Charging Process

Keep an eye on the charging process and the charger's indicator lights. The charging time may vary depending on the state of the battery and the charger's specifications. Typically, it can take several hours to fully charge a depleted low-voltage battery.

  1. Disconnect and Test

Once the low-voltage battery is fully charged, disconnect the charger by turning it off and removing the clamps in the reverse order of how you connected them. Ensure the clamps do not touch each other or any metal surfaces.

  1. Test the Low-Voltage Battery

Before closing the hood or battery compartment, it's a good practice to test the low-voltage battery's voltage using a multimeter to confirm that it has reached an appropriate level (usually around 12.6 volts when fully charged).

  1. Reassemble and Start Your EV

Close the hood or battery compartment, and you're ready to start your EV. The low-voltage battery should now have enough power to run various vehicle systems and electronics.


Charging the low-voltage battery of your electric vehicle is a straightforward process that can help ensure your EV runs smoothly. Regular maintenance and monitoring of this battery are essential for maintaining the overall health and functionality of your electric car. By following this step-by-step guide, you can confidently charge your low-voltage battery when needed and continue to enjoy the benefits of electric mobility.