Car batteries are standardized by BCI (Battery Council International) group sizes that specify physical dimensions, terminal configuration, and mounting requirements. Choosing the correct battery group size ensures proper fitment, electrical compatibility, and reliable starting power. This comprehensive guide covers BCI group sizes, dimensions, CCA ratings, and vehicle-specific fitment information.
| Group Size | Dimensions (L×W×H) | Typical CCA Range | Common Vehicles | Terminal Type |
|---|---|---|---|---|
| 24 | 10.25" × 6.8" × 8.9" (260×173×225 mm) | 500-750 CCA | Honda Civic, Accord, Toyota Corolla, Mazda3 | Top post |
| 24F | 10.9" × 6.9" × 8.9" (277×175×225 mm) | 650-800 CCA | Honda Accord, Acura, Nissan Altima, Infiniti | Top post |
| 35 | 9.1" × 6.9" × 8.9" (230×175×225 mm) | 550-650 CCA | Nissan, Subaru, Toyota, Mazda (Japanese imports) | Top post |
| 51R | 9.4" × 5.1" × 8.9" (238×129×225 mm) | 430-550 CCA | Honda Civic, Mazda Miata, older Japanese cars | Top post |
| 65 | 12.1" × 7.5" × 7.6" (306×190×192 mm) | 750-850 CCA | Ford F-150, Mustang, Mercury, Lincoln | Top post |
| 75 | 9.1" × 7.1" × 7.5" (230×180×190 mm) | 650-750 CCA | GM mid-size cars, Buick, Oldsmobile | Side post |
| 34 | 10.2" × 6.9" × 7.9" (260×175×200 mm) | 650-800 CCA | Chrysler 300, Dodge Charger, Jeep Grand Cherokee | Dual post |
| 34/78 | 10.2" × 6.9" × 7.9" (260×175×200 mm) | 650-850 CCA | GM, Chrysler, Dodge vehicles (dual terminal) | Dual (top + side) |
| 48 | 11.8" × 6.9" × 7.6" (300×175×192 mm) | 700-800 CCA | Volkswagen, Audi, BMW, Mercedes-Benz, Porsche | Top post |
| 49 | 15" × 6.9" × 7.5" (381×175×190 mm) | 850-950 CCA | BMW, Audi, Mercedes-Benz (larger models) | Top post |
| 94R | 12.4" × 6.9" × 7.5" (315×175×190 mm) | 800-850 CCA | BMW, Mercedes-Benz, Volvo, Saab | Top post |
| H5 | 10.9" × 6.9" × 7.5" (277×175×190 mm) | 650-750 CCA | BMW 3-Series, Mercedes-Benz C-Class | Top post |
| H6 | 11.8" × 6.9" × 7.5" (300×175×190 mm) | 700-800 CCA | BMW 5-Series, Mercedes-Benz E-Class, Audi A6 | Top post |
| H7 | 12.8" × 6.9" × 7.5" (325×175×190 mm) | 800-900 CCA | BMW X5, Mercedes-Benz GL-Class, Audi Q7 | Top post |
| H8 | 13.9" × 6.9" × 7.5" (353×175×190 mm) | 900-950 CCA | BMW 7-Series, Mercedes-Benz S-Class, Range Rover | Top post |
| Make | Common Models | Typical Group Sizes | Notes |
|---|---|---|---|
| Honda | Civic, Accord, CR-V | 24, 24F, 51R | 24F most common on newer models |
| Toyota | Corolla, Camry, RAV4 | 24, 24F, 35 | 35 common on imports, 24/24F on US-built |
| Nissan | Altima, Sentra, Rogue | 35, 24F, 51R | 35 most common across lineup |
| Mazda | Mazda3, CX-5, CX-9 | 35, 24, 51R | 35 standard on most models |
| Subaru | Outback, Forester, Impreza | 35, 25 | 35 most common |
| Ford | F-150, Mustang, Explorer | 65, 26, 48 | 65 for trucks, 48 for smaller cars |
| Chevrolet | Silverado, Equinox, Malibu | 34/78, 48, 65 | 34/78 (dual post) very common |
| GMC | Sierra, Terrain, Acadia | 34/78, 48, 65 | Same as Chevrolet (GM vehicles) |
| Dodge | Ram, Charger, Durango | 34, 34/78, 65 | 34 series common on cars, 65 on trucks |
| Jeep | Wrangler, Cherokee, Grand Cherokee | 34, 34/78, 48 | 34/78 most common |
| BMW | 3-Series, 5-Series, X5 | H5, H6, H7, 94R | H-series standard; 94R on some models |
| Mercedes-Benz | C-Class, E-Class, GLE | H5, H6, H7, H8, 49 | Larger H-sizes on luxury models |
| Audi | A4, A6, Q5, Q7 | H5, H6, H7, 48 | H-series most common |
| Volkswagen | Jetta, Passat, Tiguan | 47, 48, H5 | 48 very common |
| Hyundai | Elantra, Sonata, Tucson | 24, 24F, 35, 48 | Varies by model year |
| Kia | Forte, Optima, Sorento | 24, 24F, 35, 48 | Similar to Hyundai (same parent company) |
| Group | Length | Width | Height | Terminal | Typical Use |
|---|---|---|---|---|---|
| 22F | 9.5" | 6.9" | 8.3" | Top | Older import vehicles |
| 24 | 10.25" | 6.8" | 8.9" | Top | Japanese vehicles (Honda, Toyota) |
| 24F | 10.9" | 6.9" | 8.9" | Top | Honda Accord, Nissan Altima |
| 25 | 9.1" | 6.9" | 8.9" | Top | Nissan, Infiniti, some Hyundai |
| 26 | 8.2" | 6.8" | 7.3" | Top | Compact cars, older Honda Civic |
| 26R | 8.2" | 6.8" | 7.3" | Top | Japanese compact cars (reverse terminal) |
| 27 | 12.1" | 6.8" | 8.9" | Top | Heavy-duty, commercial trucks |
| 27F | 12.4" | 6.8" | 8.9" | Top | Commercial vehicles, trucks |
| 31 | 13" | 6.8" | 9.4" | Top | Tractors, commercial equipment |
| 34 | 10.2" | 6.9" | 7.9" | Dual | Chrysler, Dodge, GM mid-size |
| 34/78 | 10.2" | 6.9" | 7.9" | Dual | GM, Chrysler (top + side posts) |
| 35 | 9.1" | 6.9" | 8.9" | Top | Nissan, Subaru, Toyota, Mazda |
| 40R | 10.9" | 6.9" | 7.1" | Top | Older domestic vehicles |
| 41 | 11.8" | 6.9" | 7.6" | Top | Older European vehicles |
| 42 | 9.7" | 6.9" | 6.9" | Top | Older BMW, European imports |
| 47 | 9.4" | 6.9" | 7.5" | Top | Volkswagen, Audi (H5 equivalent) |
| 48 | 11.8" | 6.9" | 7.6" | Top | VW, Audi, BMW, Mercedes-Benz |
| 49 | 15" | 6.9" | 7.5" | Top | BMW, Mercedes-Benz (large models) |
| 51 | 9.4" | 5.1" | 8.9" | Top | Japanese compact cars |
| 51R | 9.4" | 5.1" | 8.9" | Top | Honda Civic, Mazda Miata (narrow) |
| 58 | 9.4" | 7.3" | 7.6" | Top | Cadillac, older GM luxury |
| 65 | 12.1" | 7.5" | 7.6" | Top | Ford F-150, Mustang, trucks |
| 75 | 9.1" | 7.1" | 7.5" | Side | GM mid-size (side post terminals) |
| 78 | 10.2" | 6.9" | 7.9" | Side | GM vehicles (side post only) |
| 85 | 9.1" | 6.9" | 11.4" | Top | European vehicles (tall battery) |
| 86 | 10.9" | 6.9" | 7.5" | Top | Older European imports |
| 90 | 11.8" | 6.9" | 7.6" | Top | Older European vehicles |
| 91 | 13" | 6.8" | 7.6" | Top | Older European vehicles |
| 93 | 13.6" | 6.8" | 7.6" | Top | European luxury vehicles |
| 94R | 12.4" | 6.9" | 7.5" | Top | BMW, Mercedes-Benz, Volvo |
| 95R | 12.4" | 6.9" | 8.9" | Top | Volvo, Saab (tall European) |
| 96R | 9.4" | 6.9" | 7.5" | Top | Honda Insight, Fit (small hybrids) |
The Battery Council International (BCI) established standardized group sizes to ensure consistent battery dimensions, terminal placement, and hold-down configurations across manufacturers. The group size (e.g., "24F", "35", "65") specifies the battery's physical footprint and terminal arrangement, ensuring proper fitment in your vehicle's battery tray.
Number only (e.g., 24, 35, 65): Standard BCI size designation. Number + F (e.g., 24F, 27F): "F" indicates front terminal location (reversed terminal polarity from standard). Number + R (e.g., 51R, 94R): "R" indicates reverse terminal configuration (positive and negative terminals swapped compared to standard version). Number/Number (e.g., 34/78): Dual terminal configuration—both top posts and side posts for maximum compatibility. H + Number (e.g., H5, H6, H7, H8): "H" series designation for European vehicle batteries (DIN standard equivalent).
Top Post (SAE): Round posts on top of battery (11/16" positive, 5/8" negative). Most common in North America. Standard on Japanese and European vehicles. Easy to connect with standard clamps. Side Post (GM): Threaded terminals on side of battery (3/8"-16 thread). Common on GM vehicles (Chevrolet, GMC, Buick, Cadillac). Requires bolt-on connectors instead of clamps. Less prone to corrosion than top posts. Dual Post (Top + Side): Both top posts and side posts on same battery. Provides maximum compatibility. Common on Group 34/78 batteries for GM and Chrysler vehicles.
Look at the label on your existing battery. The group size is prominently displayed (e.g., "Group 24F", "35", "H6"). Also note the CCA (Cold Cranking Amps) rating to match or exceed it with your replacement.
Your vehicle's owner's manual lists the OEM battery group size in the specifications or maintenance section. This is the manufacturer's recommended size for optimal fit and performance.
Most battery retailers (AutoZone, O'Reilly, Advance Auto Parts, Interstate Batteries) offer online battery finders. Enter your vehicle's year, make, and model to find the correct group size and compatible batteries.
If replacing a dead battery and cannot read the label: Length: Measure left to right across battery tray. Width: Measure front to back. Height: Measure from tray bottom to underside of hood (allow clearance). Terminal type: Note if posts are on top, side, or both. Compare measurements to BCI group size chart to identify compatible group sizes.
Cold Cranking Amps (CCA) measures a battery's ability to start an engine in cold temperatures. Specifically, CCA is the number of amps a battery can deliver at 0°F (-18°C) for 30 seconds while maintaining at least 7.2 volts.
4-cylinder compact cars: 400-550 CCA (Honda Civic, Toyota Corolla). 4-cylinder mid-size cars: 500-650 CCA (Honda Accord, Toyota Camry). V6 mid-size cars: 650-750 CCA (Accord V6, Camry V6, Nissan Maxima). V6 SUVs/trucks: 700-800 CCA (Ford Explorer, Toyota Highlander). V8 full-size trucks: 750-850 CCA (Ford F-150, Chevy Silverado). V8 performance cars: 800-900+ CCA (Ford Mustang GT, Dodge Charger R/T). Diesel trucks: 850-1000+ CCA (diesel engines need more power to crank).
Definition: Number of minutes a fully charged battery can deliver 25 amps at 80°F (27°C) before voltage drops below 10.5 volts. Importance: Indicates how long vehicle can run on battery alone if alternator fails. Typical RC values: 60-120 minutes for passenger vehicles. Recommendation: Higher RC provides more emergency power for accessories, headlights, and getting to safety if alternator fails.
Construction: Liquid electrolyte (sulfuric acid and water) in unsealed or low-maintenance cells. Lifespan: 3-5 years. Advantages: Lowest cost ($80-$150), widely available, proven technology, easy recycling. Disadvantages: Requires maintenance (checking/adding water), can leak if tipped, off-gassing during charging. Best For: Budget-conscious buyers, vehicles with standard electrical demands, warm climates.
Construction: Improved flooded design with reinforced plates and acid circulation. Lifespan: 4-6 years. Advantages: Better cycling ability than standard flooded, 2-3× more charge/discharge cycles, supports start-stop systems, moderate cost ($120-$200). Disadvantages: More expensive than standard flooded, still requires some maintenance. Best For: Vehicles with basic start-stop systems, higher electrical demands than standard.
Construction: Electrolyte absorbed in fiberglass mat separators; sealed, valve-regulated design. Lifespan: 5-7 years. Advantages: Maintenance-free (sealed), spill-proof, excellent cycling ability (3-5× more cycles than flooded), faster recharge, better performance in extreme temperatures, supports advanced start-stop and high electrical loads, lower self-discharge (can sit longer without charging). Disadvantages: Higher cost ($180-$350+), sensitive to overcharging (needs proper charging system). Best For: Vehicles with start-stop systems, luxury cars with high electrical demands, performance vehicles, off-road vehicles, boats/RVs.
Construction: Lithium-ion technology with iron phosphate cathode. Lifespan: 8-10+ years (2000-5000 charge cycles). Advantages: Extremely lightweight (60-70% lighter than lead-acid), very long lifespan, fast charging, excellent cold-weather performance, extremely low self-discharge. Disadvantages: Very expensive ($400-$800+), requires specialized charger, not compatible with all vehicles (may trigger low-voltage warnings), limited availability. Best For: Performance enthusiasts (weight savings), off-grid/solar setups, racing, custom builds.
Vehicles with automatic engine start-stop systems require EFB (Enhanced Flooded Battery) or AGM batteries. These batteries withstand frequent cycling (100,000+ engine starts over lifespan vs. 30,000 for standard batteries). Standard flooded batteries will fail rapidly (1-2 years) in start-stop applications due to deep discharge cycling.
Many European vehicles (BMW, Mercedes-Benz, Audi, Porsche) require AGM batteries due to: complex battery management systems (BMS) that optimize charging; high electrical loads (heated seats, advanced infotainment, multiple computers); start-stop technology; battery registration requirement (vehicle computer must be reprogrammed when battery is replaced).
Hybrids have TWO batteries: High-voltage traction battery: Powers electric motor (200-400V), lithium-ion, separate from 12V system. 12-volt accessory battery: Powers lights, radio, computer systems—this is the standard automotive battery you replace. Use AGM battery for 12V system in most hybrids. Group 51R or 25 common for Toyota/Honda hybrids.
Wear safety glasses and gloves: Batteries contain sulfuric acid that can cause severe burns. Work in ventilated area: Batteries produce hydrogen gas (explosive) during charging. Remove jewelry: Rings and bracelets can short terminals and cause severe burns. Negative terminal first (removal): Always disconnect negative (-) terminal first, then positive (+). Positive terminal first (installation): Connect positive (+) first, then negative (-).
Battery registration/coding: Required for BMW, Mercedes-Benz, Audi, VW, Porsche. Use dealer scan tool or aftermarket tool (Carly, Bimmercode) to register new battery. Registers battery capacity, type, and manufacturing date. Allows proper charging calibration. Radio code: Some vehicles require radio security code after battery disconnect. Check owner's manual or dealer for code.
Keep terminals clean: Clean corrosion monthly with baking soda solution and wire brush. Check hold-down: Ensure battery is securely fastened—vibration shortens battery life. Test voltage: Use multimeter—12.6V or higher indicates full charge; below 12.4V needs charging. Load test annually: Have battery load-tested at auto parts store (free service). Check alternator: Measure voltage with engine running—13.5-14.5V indicates proper charging. Avoid short trips: Frequent short drives prevent full recharge, shortening battery life.
Slow cranking: Engine cranks slowly or struggles to start (especially cold mornings). Dim lights: Headlights dim when idling, brighten when accelerating. Warning lights: Battery or charging system warning light illuminated. Electrical issues: Power windows slow, radio resets, dashboard lights flicker. Swollen case: Battery case bulges (indicates internal failure or overcharging). Corroded terminals: Excessive white/blue/green corrosion around terminals. Age: Battery is 4+ years old (proactive replacement recommended).
Multimeter voltage test: Measure resting voltage (engine off, 12+ hours since driving). 12.6V+ = fully charged. 12.4-12.6V = 75% charged. 12.2-12.4V = 50% charged, needs charging. Below 12.2V = discharged, charge and retest. Load test (auto parts store): Battery loaded with high current draw for 15 seconds. Measures voltage drop under load. Determines actual capacity vs. rated capacity. Free at AutoZone, O'Reilly, Advance Auto Parts. Alternator output test: Measure voltage with engine running at 2000 RPM. 13.5-14.5V = proper charging. Below 13.5V = weak alternator. Above 15V = overcharging (voltage regulator failure).
General rule: Only substitute if dimensions fit battery tray, terminals align with cables, and hold-down bracket secures battery. Close substitutes (verify fitment): 24 ↔ 24F (similar size, reversed terminals). 35 ↔ 25 (nearly identical dimensions). 34 ↔ 34/78 (same size, dual terminal adds side posts). 48 ↔ H6 (European equivalents). 94R ↔ H7 (some overlap in European vehicles).
Installing a smaller group size (e.g., Group 35 instead of specified 24F) results in: insufficient CCA for engine (hard starting in cold weather); shorter reserve capacity; battery shifts in oversized tray (poor electrical connection, safety hazard); wasted space in battery tray.
Installing a larger group size than specified causes: physical fitment issues (battery too long, wide, or tall); terminal misalignment (cables too short or won't reach); hood clearance problems (battery too tall); hold-down bracket won't secure battery; electrical issues if terminals positioned incorrectly.
Most automotive batteries carry 2-5 year warranties with two periods: Free replacement period: Full warranty coverage (1-3 years). Battery replaced free if it fails. Prorated period: Partial refund based on remaining warranty (remaining 1-3 years). You pay percentage based on age. Example: "3-year free replacement + 2-year prorated" = 5-year total warranty. Free replacement if fails in first 3 years. Years 4-5: prorated refund toward new battery.
Never trash batteries: Illegal in all 50 states—batteries contain lead and sulfuric acid (hazardous waste). Core charge: $10-$20 deposit added to new battery purchase, refunded when old battery returned. Recycling locations: Auto parts stores (free), scrap metal yards (may pay for battery), household hazardous waste facilities, auto repair shops. Environmental impact: Lead-acid batteries are 98% recyclable—most recycled consumer product in America.
Yes, recommended. Higher CCA provides better cold-weather starting and longer cranking ability. No electrical system damage from higher CCA (voltage remains 12V). Match or exceed OEM CCA rating, especially in cold climates or for older vehicles.
Hard starting in cold weather. Insufficient power to crank engine, especially winter mornings. Premature starter motor wear. Battery works harder, shortens lifespan. Not recommended—always match or exceed OEM CCA specification.
Typical lifespan: 3-5 years for standard flooded batteries. 4-6 years for EFB batteries. 5-7 years for AGM batteries. Factors affecting lifespan: Climate (extreme heat shortens life more than cold). Driving habits (short trips prevent full recharge). Electrical loads (high accessory use). Maintenance (clean terminals extend life). Quality (premium batteries last longer).
Yes, recommended for storage longer than 2 weeks. Disconnect negative terminal or use battery disconnect switch. Alternatively, connect to battery tender/trickle charger. Prevents parasitic drain from vehicle electronics (clock, alarm, computer memory). Battery fully discharged after 3-6 months of sitting.
Yes. Group size doesn't affect jump-starting. All automotive batteries are 12-volt systems. Jump-starting provides temporary power to crank engine. Use proper jumper cables and procedure: Positive (+) to positive (+), negative (-) to ground (engine block), not dead battery negative terminal.