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Published 07:00 AM, Tue September 22, 2015

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Charging a dead car battery is more than simply hooking up a charger if you want to do this job safely. You should know which terminal to remove first if you have to remove the battery, which terminal to hook up first on the charger, how long to charge a dead car battery and more.

Getting Ready to Charge

Before we get into how to charge a car battery at home, you need to know how to prepare to charge the battery. It is very easy to get a good shock if the battery does have some juice. Before you even get started, if you have to remove the battery from the vehicle to charge it, be sure you have the tools for the job. Some batteries are easily accessible; however, some are under or in the fender and some may even be in the trunk or under the seat depending on the make and model of your vehicle.

How to Jump a Car Battery

Be sure all accessories are off and the lights, including the interior light, are off. If you have anything on, it could cause the battery to arc while you are working with it.

Once you get down to the battery, remove the negative or ground cable first. This is always the black cable unless someone replaced the cables with the wrong colors. If you look on the top of the battery, you can see which is which – the ground cable will have a negative (-) sign and the power or positive cable will have a plus (+) sign.

Clean the battery terminals with a terminal cleaning brush and a mixture of baking soda and water to neutralize the battery acid. If the battery terminals and posts have a lot of acid buildup, wear eye protection and a mask so the airborne corrosion does not contact your eyes, nose and mouth. Don't touch your face until after you've washed your hands.

If the battery has removable caps, carefully pry the caps off and check the level of the water. If any of the cells looks low, add distilled water only; and take care to not overfill the battery. Most batteries today are “maintenance-free” so you won't be able to open them to check the acid level.

Hooking up the Battery Charger

Follow the instructions for your particular charger. Basic instructions for most chargers include:

  • Make sure the charger is off.

  • Hook-up the positive cable on the charger to the positive terminal on the battery.

  • Hook up the negative cable on the charger to the negative terminal on the battery.

  • Set the charger to the slowest charge rate.

  • Turn on the charger and set the timer.

When removing the charger, turn it off first, then remove the positive then negative cable.

How Long Should You Charge a Car Battery?

If the battery voltage is below 11.85 and your charger is putting out a 5-amp charge rate, it will take about 12 hours to fully charge a battery with 400 to 500 cold cranking amps. The same battery will take about 6 hours to fully charge if the charge rate is 10 amps. The lower the open circuit voltage in the battery and the more cold cranking amps, the longer it will take to charge the battery.

If a cell is bad, the battery won't hold a charge. In this case, bring your battery or your vehicle with your battery to a local Meineke Car Care Center and we will change your vehicle's battery.

  • Jayant Sharma

    Nice information for charging a dead battery using jump starts.

    • O Henry

      No, it’s not “nice information” – it’s partial information, and wrong at that. Never connect the negative (black) jumper cable to the terminal of the battery being charged!

      • Anthony Hinrichs

        Why not? Where should the negative terminal of the charger be connected? If battery charger has 3 choices: Manual, Automatic, Deep Cell – which is the slowest rate? The above says”Set charger to slowest charge rate.”

        • O Henry

          When you charge a lead-acid battery, small amounts of hydrogen and oxygen are generated (especially if you overcharge the battery or use jumper cables). The hydrogen gas collects at the negative post and the oxygen collects at the positive post. Removing the charger clamp from the negative post can cause a small spark, which would ignite the hydrogen. IF there’s enough hydrogen there, it can explode, sending shrapnel flying. You don’t want that…

          If the car has a negative ground – and only a few old cars like a pre-1975 VW Beetle have positive ground – you don’t need to connect the charger to the battery, since connecting it to any place that’s grounded will complete the circuit. Clamp the charger onto a bolt on the engine or some place on the body that isn’t painted. Lots of cars have a specially marked post on the opposite side of the engine compartment for charging or jumping the battery.
          As to what setting to use, I have no idea. You might be able to find a copy of the owner’s manual online for your specific charger somewhere.

          • Frankie D

            Exactly! Well done.

  • joeflyde

    Great info!

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