When to replace a car battery

Car batteries may need to be replaced several times during a vehicle's lifetime. How to know when to buy a replacement.

With proper care and maintenance, an average car should reach over 100,000 miles or more. But chances are the car's original battery will not be in place when the odometer turns over. This is because car batteries have definite shelf lives, and no amount of maintenance or care can reverse the effects of chemicals on metal. At some point in every car's lifetime, its battery must be replaced. Here are some tips on knowing when to exchange an old car battery with a new one:

1. Extreme weather conditions. The battery which served you so well in Miami Beach may suddenly fail you completely in Fargo. This is because most car batteries are rated by a measurement called 'cold amperage'. Under normal weather conditions, a battery with a low number of cold cranking amps will reliably start any car. But if that car remains in extremely cold climates for very long, the amount of energy needed to turn the frozen flywheel will exceed the amount of power available in the battery. If you've relocated from a warmer climate to an extremely cold one, you'll need to replace your old battery with one designed for winter weather. Consider a minimum rating of 600 cold cranking amps for most
areas with notoriously harsh winters. If practical, keep you car's battery warm through indoor storage or a judiciously-placed worklight in the engine compartment.

2. Excessive wear and tear. We've all left our headlights on or failed to deactivate a battery-draining alarm system. Ordinarily the battery should still have enough power to start the vehicle, allowing the alternator to restore power to the battery as it turns. But sometimes the battery's power has truly been reduced to zero. A power boost from jumper cables and a second battery connection may allow the car to start, but the battery itself can only take so much abuse. Think of a working car battery as a campfire. When it's fully charged, it has a tremendous amount of potential energy just waiting for a signal to go. After a few hours of non-essential use, it can still give off steady energy but it's beginning to weaken. Once it has been drained completely, it needs more 'firewood' added or else it will not have the strength to recover. Most of the time a long run with the alternator or a battery recharger will bring the battery back to service, but sometimes it's not enough. Extremely weak batteries which can no longer hold a charge must be replaced.

3. Damage to the battery casing. If a battery is severely damaged or otherwise compromised following an accident, it should be replaced immediately. Car battery cells used to be more accessible to owners, but modern batteries are often sealed shut at the factory. Any cracks in the body of the battery could cause dangerous leaks of sulphuric acid or other chemicals. If the battery was not fully clamped down and the car had a sudden shift in direction, the battery could have been damaged.

4. End of a warranty period. Most new car batteries come complete with a warranty covering any defects or damages to the battery itself. Once this protection has elapsed, however, it falls on the driver to provide for a replacement battery (which may be expensive) or repairs. If a battery shows signs of weakening and is not covered under any warranty, it may be better financially to invest in a new battery instead of worrying about a six year old battery which may fail soon.

5. No longer holding a charge. Many times the first hint of a battery problem shows up during the starting process. The starter is a small but powerful electric motor which depends on the car's battery for its energy. Once the key has been turned in the ignition, a circuit between the battery and the starter is completed through a solenoid switch. In an ideal world, the starter motor's shaft spins a small gear at the tip called a bendix, which in turn connects with the main engine's flywheel. If the bendix fails to meet the flywheel, the engine simply won't start. The result is a spinning shaft with nowhere to go.

If the car battery is too weak to provide a sufficient charge to the starter, the solenoid switch will not function correctly. It will make a distinctive clicking sound. This clicking should indicate to the driver that the battery is not fully charged. It will need to be recharged with professional equipment or jumpstarted. But a simple procedure called a load test can be performed to determine if the battery is ready to be replaced. A serviceman will attach a voltmeter to the battery's terminals while the car is running. A switch on the voltmeter will then change the power load from the alternator to the battery alone. Sometimes a weak alternator will be the culprit, but other times the test will reveal a weak battery not capable of holding a charge. This means the battery must be replaced.