For 1990-2009 cars

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.

• | 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 faulty generator

- | A faulty generator voltage regulator

- | A loose generator B+ Nut

- | Open Generator B+ Link or Wire

• | 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 retainer

• | Power failure caused by any of the following conditions:

- | A shorted or pinched wire

- | Open or intermittent battery cable continuity

- | Inadequate ground circuit to the vehicle chassis

• | Extended vehicle storage

• | Extended cranking periods due to a possible fuel or ignition system problem.

• | Incorrect interpretation of the battery's built-in hydrometer.

• | There has been an insufficient ampere-hour charge rate for a discharged battery.

• | There is a continuous current draw on the battery through excessive parasitic drain.

• | The battery is old.

Self-discharge is always occurring as a result of internal chemical reactions, even when the battery is not connected. In hot weather this chemical reaction is increased dramatically. This is why the number of discharged batteries will increase in very hot weather.

### Electrolyte Freezing

The freezing point of the electrolyte depends on the specific gravity of the electrolyte. A fully charged battery will not freeze until the ambient temperature is below -54°C (-65°F). However, a battery with a low state of charge may freeze at temperatures as high as -7°C (20°F). Ensure that the battery maintains a nominal state of charge in order to prevent electrolyte freezing and permanent battery damage.