Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns.
How to perform a battery voltage test on a home standby generator with a multimeter
Using a multimeter to check the voltage on a 12V home standby generator is a straightforward process. This article will guide you through the steps necessary to safely and accurately perform this task.
Environment
This article applies to Generac air-cooled Guardian Series 10-26 kW generators.
What you will need
- A digital multimeter capable of measuring DC voltage up to at least 20V
- Safety goggles and gloves to protect against potential acid spills and electrical hazards.
Safety first
Before you begin, ensure that the generator is turned OFF and disconnected from any power sources to prevent any accidental startup. Wear safety goggles and gloves to protect yourself from battery acid and electrical hazards. See below for steps on how to safely disconnect a home standby generator battery.
Step-by-step guide
Prepare your multimeter
Set your multimeter to the DC voltage setting. This is often denoted by a "V" with a straight line above it. If your multimeter has multiple ranges, select a range that can measure up to 20 volts to accommodate the battery's full charge voltage, which is 12.6 volts or above.
Locate the Battery
Open the generator's battery compartment to access the battery. See How Do I Remove the Generator Side Panel? to get access to the battery compartment.
Inspect the Battery
Visually inspect the battery for any signs of damage, corrosion, or leakage. Clean any corrosion from the battery terminals with a brush before testing, as this can affect your reading.
Connect the multimeter
- Connect the red (positive) probe of the multimeter to the positive terminal of the battery, which is usually marked with a "+" and is red.
- Connect the black (negative) probe to the negative terminal of the battery, typically marked with a "-" and is black.
Read the voltage
With both probes securely in contact with the battery terminals, read the voltage display on the multimeter:
- A fully charged 12V battery will read 12.6 volts or greater.
- Reading between 12.4V - 12.6V indicates the battery is partially charged and may require recharging.
- Reading below 12.4V indicates a partially discharged state, and anything below 12 volts signifies a discharged battery needing recharging or possible replacement.
For more information on battery replacement see Selecting and Replacing a Battery for a Home Standby Generator.
To replace the battery, contact a Generac Authorized Service Dealer for help, or if comfortable with the process, do it yourself: How do I replace the battery on my home standby generator?
Understanding voltage reading
- 12.6V or higher - fully charged battery in good condition.
- 12.4V - 12.6V - The battery is partially charged and may require recharging.
- Below 12.4V battery is discharged and needs to be recharged. If it doesn't hold a charge, it may need to be replaced.
- Consistently Low Readings: If after charging, the battery consistently shows a reading below 12 volts, it may be failing and require replacement.
The charge cycle for a home standby generator is 18 hours. After the charge cycle has completed, if the battery has not reached 12.6V the generator should throw an alarm "Charger Warning".
To learn more about the charge cycle, see Understanding the Home Standby Generators Charging System for more information.
See Home Standby Generator Battery Alarms and What they Indicate for more information on battery alarms.
After checking
- Disconnect the multimeter probes, starting with the black (negative) probe, followed by the red (positive) probe.
- Ensure the battery terminals are clean, tight, and secure.
- Reinstall the side and front generator panels.
- Set the generator back to AUTO.
Additional troubleshooting
