01
Group size is physical
A battery group number describes case dimensions and terminal arrangement as well as fit. A battery can have enough CCA and still be wrong for the tray, cable reach or terminal orientation.
Parts & compatibility
Which battery does my standby generator need?
Search by exact model or model family. We show group size, CCA, quantity and compatibility notes only where a manufacturer manual, specification sheet or accessory catalog supports the requirement.
Verified model database
Find your battery
If your exact model is not listed, do not assume another model uses the same battery. We add entries only when a manufacturer manual, specification sheet or accessory catalog supports the requirement.
Verified battery specification
Generac Guardian 10kW
Battery
Group 26R, 540 CCA minimum OR Group 35 AGM, 650 CCA minimum
Quantity / system
1 × 12V
Compatibility note
Verified on Generac's current 10/14/18 kW Guardian specification sheet and model page. Do not apply this automatically to PowerPact or newer cellular-series models.
Chemistry / format: Flooded Group 26R or AGM Group 35, as specified
View official source ↗Next step after checking fit
Need a battery replacement or generator service?
Use your exact generator model and serial number before ordering. If the generator still will not start, a qualified standby-generator service provider can check the battery, charging system and related faults rather than assuming a battery purchase will solve the problem.
Before you buy
Four battery details that are easy to confuse.
02
CCA is a minimum, not a model name
Cold-cranking amps matter for starting performance, especially in cold weather. Do not replace a required group/type with a physically different battery simply because its CCA number is higher.
03
Quantity changes the system voltage
Some Champion standby models use two 12V batteries wired in series for a 24V starting system. Replacing only one mismatched battery is not the same as replacing a single-battery 12V system.
04
Model revisions matter
Manufacturers change components over time. Use the generator model and serial number when the manufacturer provides serial-specific documentation or parts lookup. Manufacturer product pages can change, so confirm the battery specification for your exact serial number before purchasing; do not rely on a similar model or an older saved listing.
What the verified data shows
There is no universal “standby generator battery.”
Current manufacturer documentation shows meaningful differences even inside one brand. Older/currently documented Guardian 10/14/18 kW families can specify Group 26R 540 CCA minimum or Group 35 AGM 650 CCA minimum, while Generac model 7257 and the other listed newer Generac models specify BTX30L AGM with a 400 CCA minimum. That means even two Generac units with the same advertised kW can require different battery formats when they come from different generations. Cummins QuietConnect RS13A/RS17A/RS20A uses Group 51R 450 CCA, while larger Cummins models move into Group 26, Group 34 and model-specific cold-start configurations. Champion 14 kW and 22 kW aXis systems use two batteries in series rather than one.
Cold-weather note
More CCA is not the whole winter answer.
Manufacturers may specify heater kits, different battery options or model-specific cold-start configurations. Battery capacity is only one part of cold-weather reliability; oil, breather icing, fuel delivery, charger health and the exact generator's approved accessories also matter.
Open cold-weather guide →Source standard
How models enter the finder.
A model is added only when we can tie its battery requirement to manufacturer documentation. Preferred evidence is a current model manual or specification sheet, followed by an official manufacturer accessory catalog or support page. Retail listings and forum posts are not enough by themselves. When a manufacturer gives temperature-dependent alternatives, the finder describes the condition instead of flattening it into one universal recommendation.
Frequently asked battery questions
Can I use a battery with higher CCA than the manual minimum?
Higher CCA by itself does not prove compatibility. The battery still needs the correct group size, terminal layout, chemistry where specified, physical fit and system voltage. Use the manual requirement as the starting point.
Does every Generac air-cooled generator use Group 26R?
No. Generac model 7257 and the other listed newer Generac models specify BTX30L AGM with a 400 CCA minimum, while documented Guardian 10/14/18 kW families list Group 26R or Group 35 AGM options. The exact model and generation matter more than the kW label alone.
Why does my Champion standby generator need two batteries?
Selected Champion aXis models use two 12V starting batteries wired in series for a 24V starting system. The exact group and CCA differ by model, so replace batteries according to the model manual rather than a brand-wide rule.
What if my model is not listed?
Use the manufacturer's serial/model lookup or operator manual. The finder intentionally leaves gaps rather than borrowing specifications from a similar-looking generator.