Skip to main content

How to Use a Portable Car Battery Charger

If your car battery is dead, your can safely connect it to a charger and get your car running again.


  • Step 1: Protect yourself Wear protective clothing and eye protection. Remove any jewelry, never put your face near the battery, and keep the charger as far away from the battery as the cables permit.
  • Step 2: Determine battery voltage Consult your owner's manual to determine your battery's voltage and make sure it matches the charger's DC output voltage.
  • Step 3: Identify the battery posts Identify the positive and negative terminals on your car's battery. The positive terminal with be marked with a plus sign, the letter P, or the abbreviation POS. The negative terminal will be marked with a minus sign, N, or NEG.
  • Step 4: Connect positive clip Make sure the charger is unplugged and turned off. If the car has a negative ground, as most do, connect the positive charger clip to the positive battery post. Consult your owner's manual to determine whether your car has a remote positive terminal located away from the battery -- if it does, use the remote terminal for charging.
  • TIP: The positive charger clip will be red and the negative charger clip will be black. Be sure to connect the positive clip first.
  • Step 5: Connect the negative clip Connect the negative charger clip to the car's frame or engine block as far away from battery as the clip's cable will allow. Always connect the negative clip to a heavy-gauge metal part of the frame or engine block -- never the carburetor, fuel lines, or sheet-metal body parts.
  • Step 6: Connect to a positive ground Connect the negative charger clip to the negative, ungrounded battery post in the unlikely event that your car has a positive ground. Then connect the positive clip to the car's frame or engine block as far away from the battery as the clip's cable will allow.
  • Step 7: Charge a battery outside of the car Charge a battery outside of a car by determining the post polarities. Attach a jumper cable or a 6-gauge, insulated battery cable that is at least 2 feet long to the negative battery post. Connect the positive clip to the positive post. Connect the negative clip to the free end of the cable.
  • TIP: Do not face the battery when you make the final connection.
  • Step 8: Turn the charger on Set the voltage switch to 6 or 12 volts, depending on the battery. Then set the rate switch to your desired charge rate, either 2, 6, 12, or 30 amps. If your charger is equipped with an automatic/manual charge mode switch, set it to accommodate your battery and set the timer. Then plug the cord into a grounded outlet and turn it on.
  • TIP: Do not touch the charger clips while the charger is turned on.
  • Step 9: Turn the charger off Turn the charger off when your battery's done charging by unplugging the AC cord, switching the unit off, and removing the charger clip connected to your car's frame. Then remove the clip connected to battery post, put the charger away, and start your car.
  • FACT: During his 2008 presidential campaign, Arizona Senator John McCain proposed offering a national prize of $300 million for anyone who could develop a better, more efficient car battery.

You Will Need

  • Protective clothing
  • Eye protection
  • Owner's manual
  • Car battery
  • Battery charger
  • Jumper cable or 6-gauge
  • insulated battery cable

Popular Categories