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.
Selecting and replacing a battery for a home standby generator
Selecting the right battery for your generator and understanding how to replace it are crucial for maintaining its efficiency and longevity. This article guides battery selection and replacement.
Note: New home standby generators do not come with a battery, and it must be purchased separately.
Environment
This article applies to all Guardian air-cooled Home Standby Generators 10 kW -26 kW
Home standby generator selection
Specifications
Voltage
Home standby generators require a 12-volt DC battery to function correctly.
Type
There are two recommended types of batteries for the generator:
- Group 26R with a minimum Cold Cranking Amps (CCA) of 540.
- Group 35AGM with a minimum CCA of 650
Cold Cranking Amps (CCA)
CCA measures a battery’s ability to start an engine in cold temperatures. The higher the CCA, the better the battery will perform in colder climates.
Understanding your batteries Group Type and CCA
- The 12V Group 26R 540 CCA battery is commonly used in Generac home standby generators for its reliable starting power and performance in various temperatures.
- The "CCA" rating indicates the battery's ability to start an engine at 0 degrees F (-18 C) for 30 seconds while maintaining a voltage of at least 7.2 volts.
- The "Group 26" designation for the battery specifies a particular set of physical dimensions. For Group 26 the dimensions are approximately 8.2 inches in length, 6.8 inches in width, and 7.8" inches in height.
- The "R" in the 26R designation refers to the polarity and placement of the battery terminals. "R" stands for "Reverse", indicating that the polarity of the terminals is reversed from the standard orientation.
- The designation is crucial because it affects how the battery fits into and connects to the generator's electrical system. Using a battery with the incorrect terminal orientation can lead to cable length and routing issues, making it impossible to properly or safely install the battery.
Generac Home Standby Battery Part Number: 0H3421S Exide Group 26R 12V 540CCA
Always consult the Owner's Manual for battery specifications. For further assistance or battery recommendations for specific geographical areas, contact a local Independent Authorized Service Dealer (IASD).
See: How Can I Find a Generac Service Dealer in My Area?
Where to purchase
Replacement batteries can be purchased at automotive stores, specialized battery stores, or from authorized dealers that sell generator accessories and parts.
Battery replacement
Battery disposal
Dispose of batteries according to state and local regulations. It is essential to follow all guidelines to prevent environmental harm.
Additional battery and battery charger facts
- Home standby generators can use either flooded lead acid (require distilled water) or AGM.
- Battery charging on stationary (air and liquid-cooled) is by built in Automatic Float Charger. This type of charger will safely charge the battery to full charge, then reduce the charge rate to the minimal amount of power needed to keep the battery charged and support the power needed for the engine control board (will not overcharge the battery). To learn more about the charging system, see Understanding the Home Standby Generators Charging System.
Common questions
Marine batteries
Marine batteries are batteries that cost more but perform the same as automotive batteries. In some cases, they are designed for easy of connection in a boat application. There is no benefit in using “marine batteries” outside of some special marine and RV applications.
There is also a specialized marine battery called a “Deep Cycle Marine Battery”. Again, a more expensive battery. The primary use is for deep cycle marine batteries is electric trolling motors and is designed to better survive multiple charge and discharge cycles.
Wet cell vs. lead acid
A wet cell is a lead-acid battery. The most common type of automotive/generator battery is a “Wet Cell lead acid battery”. That simply means that the electrolyte (acid) is a liquid. There is a less common “gel cell lead acid battery”. The acid in this battery is in a gel state. Used in applications where the battery can tip over.
What is an electrolyte?
The electrolyte is the acid in a battery. It can be liquid or gelled. The electrolyte (acid) is put in the battery at time of battery activation and never added later. If a wet cell is low on electrolyte, only distilled water can be used to top off.
Note: Most of the batteries that we use are Sealed Lead Acid Batteries. This type of battery is considered a No Maintenance Battery and should never lose electrolytes.
Is the red terminal (cable) always positive?
This is not written in stone, however, red cables and terminals typically will be positive.
In what order do you disconnect and connect the battery cables?
When disconnecting, start with the negative cable first. When reconnecting, connect the positive first, then the negative.
