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 using 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.

Note: It is also possible to check battery voltage using Mobile Link, or the generator's control panel: How to view your home standby generator's battery voltage

Environment

This article applies to:

• Generac Next Generation Series 10-28 kW air-cooled standby generators
• Generac Guardian Series 10-26 kW air-cooled generators (2017 to present)

Battery health and testing considerations

• While a multimeter can be used to verify that voltage is present in the battery, and provide voltage readings, it is not the best method for accurately gauging a battery's performance while under load.
• To precisely gauge battery health, load testing with a carbon pile or digital load tester is recommended. This method evaluates the battery's performance while under load.
• Load testing is a service provided at most automotive stores, i.e., AutoZone.

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.

Checking the voltage

• Touch the red (positive) probe of the multimeter to the positive terminal of the battery, which is usually marked with a "+" and is red.
• Touch 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 corresponding battery terminals, read the voltage display on the multimeter:

• 12.6V or higher - The battery is charged.
• 12.4V - 12.6V - The battery is partially charged and may require recharging.
• Below 12.4V - The battery is discharged and needs to be recharged. If it doesn't hold a charge, it may need to be replaced: How do I replace the battery on my home standby generator?
• Consistently low readings - If after charging, the battery consistently shows a reading below 12 volts, it requires replacement.

Note: Depending on the ambient temperature, a battery with voltage ranging from 13.5 VDC to 14.6 VDC may indicate it is in the middle of a charge cycle: Understanding the Home Standby Generator's Charging System

See here for more information on battery replacement: 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?

Generally speaking, home standby generator batteries need to be replaced every 3–5 years.

After testing

• 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.

Determining battery health

• While the voltage of a home standby generator's battery can be gauged using Mobile Link, the generator's control panel, or with a multimeter, the most accurate way to determine the battery's health is with a battery tester.
• A battery tester (carbon pile or digital) accurately tests battery health by placing a load on it for several seconds.
• If generator owners have concerns about their battery, but do not have a carbon pile tester available, the battery can be taken into a battery specialty or auto parts store, who often have the tools necessary to test the battery.

Additional troubleshooting

• If you notice an alarm in Mobile Link or at the generator's control panel related to your battery, see here: Troubleshooting home standby battery alarms and error codes
• The charge cycle for a home standby generator is 18 hours. After the charge cycle has completed, and if the battery has not reached 12.6V, the generator should throw a "Charger Warning" alarm.
• My Generator was just installed and is giving a "Charger Warning" or "Charger Missing AC Warning"
• Diagnosing Starting issues: Battery or Charger
• How Do I Inspect the Battery On My Home Standby Generator?