Generac Generator Battery Chart by kW: Group, CCA and Part Number

Generac battery chart by kW

Find your generator line and kilowatt rating, then read across. Next Generation units (2025+) take a BTX30L AGM battery, 400 CCA minimum. Guardian and earlier Evolution units take a Group 26R wet cell (540 CCA) or a Group 35 AGM (650 CCA). PowerPact takes a Group U1, 300 CCA. Each row names its Generac document and page.

Three notes that change what you buy. The Group 35 AGM option needs an Evolution controller: Generac's compatibility chart marks it "Must have Evolution controller." A0010137451 and A0010137452 are for Next Generation units only: Generac's accessories table answers "No" in its "Also Compatible with Guardian" column for them. An older spec sheet says something else for the 14/18 kW Next Generation: revision B of that sheet (07/11/2025) printed "AGM Powersport Battery Group BTX20L 310CCA minimum" with accessory A0006487350, while revision D (08/13/2026) and the owner's manual (Rev. C, 04/24/2026) print BTX30L, 400 CCA, A0010137451 / A0010137452. The chart follows the newer documents.

Not in the chart, because no Generac document we could reach states the battery: 8, 12 and 17 kW units, Nexus-era units before 2013, Synergy and CorePower, and every liquid-cooled model. For liquid-cooled units Generac's own chart says "See spec sheets and owner manuals." Use the manual for your model number; the manuals page links the ones Generac hosts.

A0010137451 vs A0010137452: what is the difference?

Generac does not say. Every Generac document checked for this page lists the two numbers together, for the same battery and the same generators: all Next Generation units from 10 to 28 kW. None gives either number a different group, rating or model, so match the specification and buy whichever is in stock.

The specification is what to match if neither number is in stock: 12 V, AGM, Group BTX30L (Generac's support articles call it Group Size 30L), 400 CCA minimum. More on the part itself: Generac A0010137452 battery.

Which battery

Generac sizes the battery by generator line and controller, not by kilowatts within a line, which is why the chart has so few distinct answers. Match the group first: Generac's battery article says it "indicates where the terminals are and the battery dimensions. The battery must fit and orientate correctly within the unit." The CCA figure is a minimum.

What size battery for a 20, 22, 24 or 26 kW Generac?

The same one, on every air-cooled Guardian in that range — which is the answer people are usually surprised by. Generac does not vary the battery by kilowatt rating within the air-cooled line; it varies it by generation and controller, and the whole 10–26 kW Guardian range shares one specification. What changes the answer is whether your unit is a Guardian, a Next Generation, or a PowerPact: a 22 kW Guardian takes a Group 26R (0H3421S), and a 22 kW Next Generation takes a BTX30L AGM (A0010137451 / A0010137452).

Two things the chart is designed to stop. First, Group 35 AGM is not the Next Generation battery — it is an alternative on Evolution-controller Guardians, and conflating the two is the most common error in third-party battery guides. Second, the Next Generation spec sheets and owner's manual word the requirement as "12 volts, AGM Powersport Battery Group BTX30L 400CCA minimum" and Generac's support articles call it "Group Size 30L"; both list the same two part numbers, so they describe the same battery.

Which model numbers that specification actually covers

Kilowatt ratings are a shorthand. The number Generac writes its documentation against is the model number on the data label inside the lid, and the owner's manual publishes the 0H3421S requirement against a fixed set of kilowatt columns rather than against the whole air-cooled range. Cross-referencing those columns with the model numbers on Generac's own kit compatibility sheet gives the list below — these are the model numbers for which the Group 26R / Group 35 AGM specification is verified in writing. Not sure of your model? See how to find a Generac serial and model number.

Model numbers Generac lists at other unit sizes — the 6, 7, 8, 9, 11, 13, 15, 16 and 17 kW units, every kVA-rated model, and the Synergy, EcoGen, CorePower and PowerPact lines — are not covered by the 10–26 kW owner's manual, so this page does not extend the 26R specification to them. Their battery is whatever their own owner's manual states. The maintenance and parts compatibility finder returns the battery requirement per model number and leaves it blank rather than guessing for exactly this reason.

Test before you buy

A dead display, a click with no crank, or a 2750 Low Battery warning all say "battery" — but Generac's starting-issues article makes the distinction that saves a purchase: if the battery is low and the display shows 2780 CHARGER MISSING AC with the utility on, the charger has no AC and a new battery will run down the same way. Fix the charger feed (usually the T1 fuse in the transfer switch — dealer) and then judge the battery.

Reading voltage without a meter: on Evolution 2.0 controllers, ESC → DATE/TIME → ENTER → MAINT → ENTER → Battery → ENTER, which shows "Good" above 12.6 V; on Evolution 1.0, ESC → BAT → ENTER; on Nexus, STATUS → DISPLAY → BATTERY VOLTAGE. Next Generation units have no display and report through the Mobile Link app. With a meter across the posts, Generac's voltage-test thresholds: 12.6 V and above charged; 12.4–12.6 partially charged; below 12.4 discharged; consistently below 12 V, replace. The article recommends a load test as well — any auto-parts store does one free.

Also worth knowing from Generac's charging-system article: the built-in charger starts an 18-hour cycle whenever the battery drops below about 12.6–12.7 V, and it charges even with the controller OFF and the MLCB OFF as long as the utility is on. So a battery that reads 12.3 V at noon may read 12.7 V by tomorrow. Give it the 24 hours Generac's 2750 article asks for before condemning it — unless it's past the five-year mark, in which case the decision makes itself.

Replacement, step by step

On a Next Generation unit, Generac publishes a separate 17-step procedure: the same fuse pull and cable order, but the charger is disconnected at connector J6, both terminals get a torque figure, and there is no setup wizard at the end.

Next Generation units have no display, so confirm the state through Mobile Link rather than an LED sequence.

Generac's article doesn't include "turn off the charger breaker" as a separate step; the fuse pull, controller OFF and utility main OFF cover it. A new battery may need an 18-hour initial charge cycle before the controller reports "Good" — that's from Generac's starting-issues article, and it's normal. The charging voltage you'll see on a meter with the utility on is about 13.5–14.6 V on Evolution units (12.2–16.0 V on Power Zone 200), temperature-compensated.

Wear eye protection. The manual's battery warning is the standard one — explosive gases while charging, no sparks or flames — and it's real: a battery that has been on a charger for years in a sealed enclosure is the one that vents.

Battery warnings and reminders on the display

Four yellow codes describe the charging circuit, all on the 2780 page: 2750 Low Battery (under 12.1 V for 60 seconds), 2760 Battery Problem (over 16 V or still drawing 600 mA after 18 hours — a shorted cell or overcharging), 2770 Charger Warning (under 12.5 V after an 18-hour charge — the battery won't come up), 2780 Charger Missing AC (no 120 V on T1). The plain-text INSPECT BATTERY reminder is different — a countdown-timer reminder, not a measurement of the battery. Clear it on Evolution units with OFF → ENTER → ENTER → AUTO, or through MAIN MENU → MAINT → "Battery Maintained"; on Power Zone 200, hold OFF three seconds. On older systems Generac's article notes that Inspect Battery can also flag a T1 wiring problem, and adds that "the T1 circuit remains live at 120 V" — leave it alone.

Cold weather

Generac recommends its cold-weather kit where temperatures "routinely fall below 32 °F." The battery warmer is the part that matters for starting: G0071010 on Guardians, G0072110 on Next Generation, kit 6808-1 on the PowerPact; thermostats switch on at 40 °F and off at 55 °F. The snowstorm-prep article's list: battery fully charged at 12.6–12.8 V, warmer fitted (but "except for AGM-style batteries"), propane above 35 %, Cold Smart Start enabled, three feet of clearance. If you'll be away, it says: OFF and remove the 7.5 A fuse.

Parts and consumables

Do I need to reset my Generac after changing the battery?

Not a "hard reset" in the sense people mean, but yes — the controller loses the clock, and that has a consequence worth understanding. The owner's manual states it in one line: "Exercise timer and current date and time must be reset if battery is discharged or has been disconnected." On a Guardian the Install Wizard appears by itself on power-up and walks you through date and time in military format; on a Next Generation you press AUTO and the unit carries on.

The reason it matters is the exercise timer. A standby generator proves itself by running for a few minutes every week, and a controller with no date has no schedule. If you skip the wizard or set the clock wrong, the unit may not exercise at all, which is exactly the failure that shows up as a no-start six months later.

What Generac does not document is a hard reset as part of a battery swap. The OFF-hold and OFF-ENTER sequences you will find described online are Generac's procedures for clearing an alarm — hold OFF for at least three seconds on Power Zone 200, or press OFF then ENTER on Evolution 1 and Evolution 2 — and they exist to clear a fault code, not to complete a battery replacement. If your generator has an active alarm after the swap, clear it with those. If it does not, there is nothing to reset beyond the clock.

How long does a Generac generator battery last?

Three to five years, per Generac's own support documentation — and the service schedule asks you to check it long before that. The owner's manual for the 10–26 kW air-cooled range lists "Check battery condition" under Schedule A, every two years or 200 hours, and prints a "Battery Inspection and Charge Check" log beneath the schedule table for recording the dates you performed it. The PowerPact manual is more granular: corrosion removal, terminal cleaning and a charge-state check yearly, plus an electrolyte level check every six months on unsealed batteries.

In practice the useful rule is calendar-based rather than test-based. A standby battery sits on a float charger in an outdoor enclosure through temperature swings, and it fails the way that batteries in that duty always fail — it tests acceptable at rest and collapses under cranking load on the coldest morning of the year. A load test at an auto-parts store is free and is the only test that catches this; a voltmeter reading of 12.6 V does not.

Replace at five years whether or not it has failed. The battery costs a fraction of a service call, and the day it matters is the day nobody is available.

Repair or replace?

Replace, on schedule. Generac's own line is three to five years, and a standby generator's battery has one job on one day. A Group 26R from an auto-parts store that meets the CCA spec does the job; Generac's branded 0H3421S is the same class of battery. The expensive mistake is the other one — a five-year-old battery that tested "fine" in July and doesn't crank in January. If the display shows a charger warning after a new battery, the problem was never the battery; see 2780.

When to call a dealer

Related pages

If you would rather look the requirement up by the number on the data label than read it off a kilowatt row, the compatibility finder on the Generac maintenance kit page returns the battery specification alongside the maintenance kit, spark plug, oil filter and air filter for the same model number, and leaves any field Generac does not publish for that unit marked as not verified.

What to check when the unit won't crank at all: Generac won't start. The four charger codes in detail: 2780 and its siblings. A weak battery is also the first thing Generac's manual tells you to check for 1505 RPM sense loss when the unit will not start — the controller is not seeing the engine signal while cranking. The full code list with reset sequences: Generac error codes. The rest of the service schedule: maintenance kit and oil.