If the battery performs satisfactorily during testing but fails to operate properly for no apparent reason, the following are some of the more important factors that may be the cause of the problem:

1. The vehicle accessories have been left on overnight or for an extended period of time without the generator operating.
2. The vehicle has been driven at slow average driving speeds for short time periods.
3. The vehicle's electrical load is greater than the generator output, particularly with the addition of aftermarket electrical accessories.
4. Conditions exist in the charging system such as electrical shorts, slipping drive belt, faulty generator or voltage regulator. Refer to Symptoms - Engine Electrical .
5. The battery has been neglected and/or abused, such as a loose battery retainer bracket or failure to maintain clean and tight battery connections.
6. The vehicle has been stored for an extended period of time without proper battery protection. Refer to Battery Electrical Drain/Parasitic Load .
7. The vehicle has received new batteries without proper charge.
8. The engine has been cranked extensively due to poor engine mechanical conditions. Refer to Engine Mechanical.
9. The built-in hydrometer has been interpreted incorrectly. Refer to Battery Hydrometer Displays Dark or Yellow Dot .
10. The battery has endured continuous current draw through increased parasitic load. Refer to Battery Electrical Drain/Parasitic Load Test for parasitic load test procedures.
11. Mechanical conditions exist in the electrical system, such as shorted or pinched wires.