If the battery tests good but still fails to perform well, the following are some of the more common causes:
| • | A vehicle accessory was left on overnight. |
| • | The driving speeds have been slow with frequent stops (stop-and-go driving). |
| • | The electrical load has exceeded the generator output (particularly with the addition of aftermarket equipment). |
| • | Existing conditions in the charging system, including the following possibilities: |
| - | An electrical short |
| - | A slipping belt |
| - | A bad generator |
| • | The battery has not been properly maintained, including the following situations: |
| - | A failure to keep the terminals tight |
| - | A failure to keep the terminals clean |
| - | A loose battery hold-down |
| • | Power failure caused by an existing mechanical condition in the electrical system, such as a short or pinched wire. |
| • | The car is in storage for extended periods of time. |
| • | Extended cranking periods caused by spark plug fouling. |
| • | The hydrometer has been read incorrectly. |
| • | There has been an insufficient ampere-hour charge rate for a discharged battery. |
| • | There is a burned out charge indicator bulb causing a NO CHARGE condition. |
| • | There is a continuous current draw on the battery through excessive parasitic drain. |
| • | The battery is old. |