Your recent article about battery ratings struck a chord with me as I also replaced my battery after having trouble starting my car. The only difference is I have had one incident since of slow cranking and one where I needed to jump-start the engine. What else could be causing this problem? Could I have purchased a defective battery?

-Paula Ferris, Dublin, Calif.

A car’s failure to start or a poor starts might be caused by a failing battery, as well as a handful of other causes. Before replacing a battery, it’s wise to have a professional check for each possibility.

Let’s start by looking at the difference between a no-crank and a no-start condition. If the engine cranks normally, but fails to start, the problem most likely lies in either the ignition or fuel system. If it fails to crank or cranks slowly, we’re looking at a battery, starter, charging system or connection fault, or a parasitic battery drain.

A battery can last from three to seven years and usually gives some warning prior to failure. Signs of a geriatric battery include slow cranking after a long period of doors open (as when cleaning the car) or on a cold morning, or noticeable brightening of the headlights as you accelerate from a stop.

Loose or corroded battery terminals also can result in these symptoms as well as a no-crank condition. Cleaning the cable connections every two years is a good idea. A screwdriver tip firmly pressed into the gap between each battery post and terminal usually will prove-out and momentarily correct a terminal-caused no-crank condition. (This does not apply to side-terminal batteries).

A professional inspection should include a battery test, using a cell conductance tester and/or a load test and a cleaning or voltage-drop test of the cable connections. Proper starter operation is next checked by noting cranking speed/tone, and if warranted, a voltage-drop test of the circuit connections. This will determine if a cranking fault lies within the starter, or if the circuit is failing to provide the necessary current for proper starter operation.

The next test is of proper alternator belt tension and charging-system performance. A loose or contaminated belt, faulty electrical connection or alternator fault could result in poor charging of the battery and occasional starting difficulties. The alternator is tested by applying a large electrical load to the vehicle (similar to turning on all accessories at once) and checking to see if the alternator can meet it.

The final check is for a possible parasitic load. This is an unacceptable draining of the battery while the vehicle is parked. While a small drain of system memories is normal, a larger drain, such as a constantly on trunk light, will run the battery down over a period of time.

As you can see, there are several possibilities that can result in a poor or no-crank condition. A professional can perform these initial tests in about a half-hour and ensure the problem is fixed right the first time. More detailed testing and repairs will require additional time.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose.