How to Fix a Car Battery That Won't Hold a Charge

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When you get into your car and turn the key, you expect it to start. That is what happens for the majority of people going through this daily ritual. However, there are some people who say a little prayer before turning the key. Why? They have a bad battery, and it is often a guessing game on whether the engine will start when they turn their key. Fortunately, there are ways to fix this situation without replacing the battery. This can be done at home with just a small investment and a few tools.

Things You'll Need

  • Protective eye wear
  • Plastic funnel
  • Battery hydrometer
  • Battery post/terminal cleaner
  • Screwdriver
  • Voltmeter with probes
  • Battery load tester
  • Battery treatment (optional)
  • 6/12-volt battery charger/starter
  • Prepare the battery. Put on the safety glasses. Clean the battery posts by placing a battery post cleaner on each battery post and twisting it back and forth until the posts become clean and bright.

  • Perform a load test. Connect the load tester to the positive battery terminal first and then to the negative post. (The positive post will be the larger of the two and will be marked with a "+".) This will prevent sparking. Switch on the load tester and check to see that the load does not drop below 12 volts. If the meter does drop to the bottom of the scale and remains there, the battery cannot be saved and must be replaced.

  • 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.

  • Perform a hydrometer test. Using the hydrometer, squeeze the bulb and insert the tube into a battery cell. Squeeze the bulb a few times to stir up the battery solution. If the solution is a dark color, the cell is bad and you will need to replace the battery. Draw the fluid up into the scale portion of the hydrometer by squeezing the bulb and releasing it while the tube is in the solution. Note which color the fluid rises to. Green means the battery is good; white, fair; and red, it needs a charge. Also, make sure the battery fluid covers the lead in each cell by at least 1/8 inch. Repeat this test on all cells. Make a note of the readings with a pen and paper.

  • Test the cells. Place the positive probe from the voltmeter on the positive battery post and the negative probe in the first cell. If the cell does not read at least two volts on the meter, there is a problem with that cell. Next place the positive probe in the first cell and the negative probe in the second cell. Then place the positive probe in the second cell and the negative probe in the third cell. Continue this until you have tested all cells. Keep track of the readings. The final reading should be zero.

  • Add the treatment chemicals (optional). To recondition the battery and clean the cells, follow the chemical manufacturer's instructions and pour the chemicals into the cells. Replace the cell covers and place the battery on a slow or "trickle" charger for at least 24 hours.

Tips & Warnings

  • Using a trickle charger is the best way to fix a battery that will not hold a charge. A battery that has been run low repeatedly needs to be slow-charged for 24 hours.
  • Always hook the positive cable up first and remove it last. This will prevent dangerous sparking.

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References

  • Photo Credit dead battery image by Katrina Miller from Fotolia.com
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