How to Recondition a Dead Car Battery

Updated July 20, 2017

With a focus on being green, more and more people are choosing to recondition their worn out automobile batteries. While it has been a practice to discard used batteries in the past, the push to recycle has finally begun to take hold in the battery business. People have been able to purchase reconditioned batteries for years, but the option of reconditioning a battery at home has not been available to the average consumer. Until now, that is.

Clean the battery posts. Put on the safety glasses. Place a battery post cleaner on each battery post and twist it back and forth until the posts become bright and shiny.

Check the battery voltage. Place one probe from the volt meter on the positive battery terminal and the other probe on the negative terminal. If the meter reads less than 12 volts, there is a problem with at least one battery cell.

Remove the cell covers. Place a screwdriver under the edge of the cell cover and gently pry it up. Remove the cover and set it aside.

Test the cells. Place a probe from the volt meter on the positive battery post and the other probe in the cell. If the cell does not read at least 2 volts on the meter, there is a problem with that cell.

Perform a load test. Connect the load tester to the positive battery terminal first and then to the negative post. This will prevent sparking. Switch on the load tester and check to see that the load does not drop below 10 volts.

Perform a hydrometer test. Squeeze the bulb of the hydrometer and insert the tube into a battery cell. Note which colour the fluid rises to. Green means the battery is good. White means the battery is fair. Red means the battery really needs a charge. Also, make sure the electrolyte fluid covers the lead in each cell by at least 1/8 inch. Repeat this test to all cells.

Add the battery treatment chemicals. Follow the chemical manufacturer's instructions on adding the chemicals. Replace the cell covers and place the battery on a charger for at least 24 hours.


When charging your battery, use a slow trickle charger. This type of charger works with the least amount of damage to the battery.


If you get battery liquid on your skin, wash it immediately with plenty of fresh water. Serious injury and burns can result.

Things You'll Need

  • Protective eye wear
  • Plastic funnel
  • Battery hydrometer
  • Battery post/terminal cleaner
  • Screwdriver
  • Volt meter with probes
  • Battery load tester
  • Battery treatment (optional)
  • 6/12-volt battery charger/starter
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