Generator batteries provide the current needed to power the starter and support control circuits during cranking. They must deliver that current instantly when utility power fails and the generator is called to start. As batteries age, cranking capacity drops even when voltage looks normal at rest.

• Cranking Power: Batteries must deliver hundreds of amps instantly to turn the starter motor and overcome engine compression during cold starts.

• Control Circuit Support: Beyond starting, batteries power the controller, fuel solenoids, and safety circuits that manage generator operation during power transfer.

Weak batteries lead to slow cranking, failed starts or intermittent starts, especially in colder weather. Repeated low voltage cranking also stresses the starter and the starter wiring.

How often should it be inspected?

Batteries are checked for age, terminal condition, connection tightness, and load performance every quarter during PM1 inspections—not just a quick voltage reading. Load testing reveals actual cranking capacity under realistic starting conditions.

Environmental Considerations: Battery life varies dramatically by climate. In hot environments like Texas and Florida, heat accelerates sulfation and electrolyte evaporation, shortening battery life. In colder climates, batteries last longer but require higher cranking amps, making load testing even more critical.

• Slow Cranking Speed: Engine turns over sluggishly, taking longer than normal to reach starting RPM.
• Clicking Sound During Start Attempt: Starter solenoid engages but lacks power to turn the engine over.
• Dimming Controller Display: Screen brightness drops or flickers during cranking as voltage sags.
• Failed Starts After Sitting Idle: Generator that previously started reliably now fails after periods of inactivity.
• Corroded or Swollen Battery Terminals: Visible sulfation or battery case distortion indicating internal failure.

“The batteries show 12.6V on my multimeter—are they good?”

Not necessarily. Resting voltage only shows battery charge level, not cranking capacity. A sulfated battery can show perfect voltage when not under load but collapse instantly when asked to deliver hundreds of amps during starting. This is why we perform load testing—applying actual cranking current for 15 seconds while monitoring voltage drop. Only this test reveals whether batteries can deliver power when your facility needs it most.