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CarMax Expert Advice on Maintaining Your Car Battery


RICHMOND, Va.--Replacing a car battery can be a hassle. That’s why CarMax, Inc. , the nation’s largest retailer of used cars, wants you to know how to keep your car battery in top-notch condition.

“Car batteries supply electrical energy to retain the memory in the onboard computers as well as the energy needed to start the engine”

“Car batteries supply electrical energy to retain the memory in the onboard computers as well as the energy needed to start the engine,” said Tom Damon, ASE Master Technician for CarMax. "Proper maintenance is vital to keep your vehicle running year round, especially during the harsh winter months."

CarMax technicians offer a few do’s and don’ts to help you safely maintain your car battery for peak performance:


  • Wear proper eye, hand and clothing protection when working with batteries.
  • Check the terminals where cables connect to be sure they are tight and corrosion free. If corrosion is present, have terminals cleaned by a professional.
  • Lubricate terminals with a dab of petroleum jelly to keep cables clean and free from corrosion.
  • Make sure the battery is firmly secured to its mounting bracket. An unsecured battery can become damaged and cause short circuits.
  • Check the fluid level unless it’s a maintenance-free battery. If the fluid is low, add distilled water. If there is no fluid visible, then replace the battery.
  • Keep your battery case clean. Dirt conducts electricity and can discharge the battery. Use a solution of baking soda dissolved in warm water to clean the battery. Wet the case and agitate with a nylon bristle brush to scrub surface. Rinse well with plain water.
  • Batteries come in many different sizes. When replacing a car battery, make sure you choose the right size for your vehicle. When it comes to car batteries, bigger is not always better.
  • Prior to disconnecting the battery, check manufacturer specifications on what items may be disrupted when disconnecting the battery. For example, the radio may require a security code when the battery has been disconnected.
  • Always disconnect the negative cable first and reconnect it last.
  • Charge battery in a well-ventilated area.


  X   If your battery is frozen, do not charge it, as it may explode! One visual sign of a frozen battery is that the sides are bowed out. This condition is dangerous; the battery will need to be replaced.
X If you need to charge your battery yourself, switch the charger to a low-charge setting. Most chargers have this feature, but if not, have a professional charge the battery.
X Don’t charge a dead battery with a car’s alternator. An alternator is not designed to function as a charger, and it may be damaged or have a shortened life as a result.
X Never lean over a battery when charging, testing, or jump-starting the engine.
X Don’t disconnect battery cables while engine is running (your battery acts as a filter).
X Don't let the battery get totally discharged. Most car batteries get their power from lead cells submerged in electrolyte and these cells can be damaged when the battery is totally discharged.
X Don’t let the battery get hot while charging.

About CarMax

CarMax, a Fortune 500 company, and one of the Fortune 2009 “100 Best Companies to Work For,” is the nation’s largest retailer of used cars. Headquartered in Richmond, Va., we currently operate 100 used car superstores in 46 markets. The CarMax consumer offer is structured around four customer benefits: low, no-haggle prices; a broad selection; high quality vehicles; and customer-friendly service. During the twelve months ended February 28, 2009, the company retailed 345,465 used vehicles and sold 194,081 wholesale vehicles at our in-store auctions. For more information, access the CarMax website at