Charging system problems often come to you as a
"no-start" complaint. The battery will have discharged and the starter
won't crank the engine. The first step is to test the battery and charge it if
necessary (fig 1).
No-Load Test
Voltage
Percent Charge
12.60V to 12.72V
12.45V
12.30V
12.15V
100%
75%
50%
25%
Readings obtained at 80°F (27°C)
Fig 1.
Click on graphic to view larger image.
Fig 1 - Measuring System Voltage Bleed the surface charge
from the battery by turning on the headlights for a minute. Measure the
voltage across the battery terminals with the lights off (see chart).
When possible, individual cell specific gravity should be checked with a
hydrometer. A load test should be done to indicate battery performance
under load. Voltage tests only tell the state of charge, not the battery
condition.
