What Size Battery Is in a 2011 BMW 328i?

The 2011 BMW 328i typically uses a Group 94R (H7) 12-volt battery, most commonly around 80–90 amp-hours (Ah) with approximately 720–900 cold cranking amps (CCA), depending on options and whether it has start-stop or high-load electrical equipment. Below is a detailed breakdown of the correct size, specifications, and what to check before replacing it.

Understanding the 2011 BMW 328i Battery Specification

The 2011 BMW 328i is part of the E90/E91/E92/E93 3 Series generation and uses a large, European-style “DIN” battery mounted in the trunk. While exact specs can vary slightly by trim and market, BMW designed this model around the 94R/H7 form factor, which fits the battery tray and works correctly with the car’s electrical management system.

Typical Factory Battery Specs

The original equipment battery in a U.S.-spec 2011 BMW 328i is usually an AGM or flooded lead-acid unit with defined dimensions and capacity. Below are the most common factory-style specifications you’ll encounter.

The following list outlines the typical key specifications BMW targets for the 2011 328i battery so you can compare them with aftermarket options.

• BCI Group Size: 94R (also known as H7 in European sizing)
• Battery Type: AGM (Absorbent Glass Mat) preferred; some trims used flooded lead-acid from the factory
• Voltage: 12V
• Amp-Hour Rating (Ah): Commonly 80–90 Ah (e.g., 80Ah or 90Ah)
• Cold Cranking Amps (CCA): Typically in the 720–900 CCA range, depending on brand and exact model
• Physical Dimensions (approximate): 12.4 in (L) × 6.9 in (W) × 7.5 in (H) — 315 × 175 × 190 mm
• Polarity/Terminal Layout: Reversed (hence “94R”): positive on the right when terminals face you
• Location in Vehicle: Trunk, right side, under trim panel

Taken together, these parameters ensure the replacement battery not only physically fits the vehicle, but also provides the right power reserve and compatibility with BMW’s charging and monitoring systems.

AGM vs. Flooded Lead-Acid: What the 328i Can Use

The 2011 BMW 328i was engineered at a time when BMW was increasingly using AGM batteries, especially on models with higher electrical load or features like EfficientDynamics. In practice, both AGM and conventional flooded lead-acid batteries appear in this model, but AGM is now widely recommended as the safer, more robust choice.

Why AGM Is Generally Recommended

Because the battery sits inside the cabin/trunk area and the 3 Series has a sensitive electrical system, BMW and many independent specialists favor AGM batteries for durability and safety.

The following list highlights the main reasons AGM batteries are typically preferred for a 2011 BMW 328i.

• Better vibration resistance: More resistant to vibration and shock in a stiff-suspension sports sedan.
• Improved deep-cycle performance: Handles repeated short trips and accessory use better than many flooded batteries.
• Spill-proof design: Safer in the trunk; greatly reduces risk of acid leakage or fumes.
• Higher power density: Delivers strong cold cranking performance in a relatively compact footprint.
• Longer service life (typically): Often lasts longer under the electrical demands of modern BMWs.

While a properly vented flooded battery can function in the 328i, choosing an AGM Group 94R battery aligns better with BMW’s later updates and most current replacement recommendations.

How to Confirm the Correct Battery Size on Your Specific 328i

Although Group 94R is standard for the 2011 328i, differences in options and regional configurations mean it is wise to verify your car’s setup before buying a replacement. This avoids compatibility issues with the battery tray, hold-downs, and electrical programming.

Checking the Existing Battery Label

The easiest and most direct way to confirm your battery size is to inspect what’s currently installed in your vehicle, provided it was correctly fitted and registered by a previous owner or shop.

The following steps describe how to confirm the current battery’s specification from inside the vehicle.

1. Open the trunk: Lift the cargo floor or right-side trim panel to access the battery compartment.
2. Locate the label: Look for a printed label on top or on the side of the battery case.
3. Identify group size: Find markings such as “94R,” “H7,” or an exact part number that cross-references to Group 94R.
4. Check Ah and CCA: Note amp-hour rating (e.g., 80Ah, 90Ah) and CCA figure (e.g., 720A, 850A).
5. Confirm battery type: Look for “AGM,” “VRLA,” or wording such as “Absorbent Glass Mat,” vs. “flooded” or no AGM marking.
6. Note the vent connection: Confirm that a vent tube is connected, especially if it is a flooded battery.

If the existing battery’s markings match a 94R/H7 profile and show a capacity in the 80–90Ah range, you are generally safe purchasing an equivalent or slightly higher-quality AGM replacement with the same physical group size.

Using VIN or OEM Part Numbers

For a more authoritative confirmation, you can check BMW’s electronic parts catalog or dealer information using your VIN.

The bullet points below summarize the common ways to verify the official battery specification tied to your individual car.

• BMW dealer inquiry: Provide your VIN to a BMW dealer parts department to get the correct official battery part number and capacity.
• Online parts catalogs: Use your VIN with OEM catalog sites (e.g., RealOEM) to see the exact factory battery spec and any superseded part numbers.
• Service history: If available, check invoices to see what battery type and rating were used during the last replacement.

By cross-checking the battery label and official part references, you can be confident that your chosen 94R replacement precisely matches what BMW intended for your 2011 328i.

Battery Registration and Why Size Matters in a BMW

Beyond physical size, the 2011 BMW 328i’s charging system is programmed to expect a specific battery capacity and type. Simply dropping in a new battery without telling the car can reduce battery life and sometimes cause electrical anomalies.

What Is Battery Registration?

BMW’s Intelligent Battery Sensor (IBS) and engine control unit track battery age and condition. When you install a new battery, these systems need to be reset so charging and load management can be optimized for the new unit.

The list below outlines the key reasons battery registration is important after replacing the battery on a 2011 328i.

• Correct charging profile: Ensures the alternator output matches the specific Ah and type (AGM vs flooded) of the new battery.
• Avoid overcharging or undercharging: Prevents premature battery wear or sulfation caused by incorrect charging logic.
• Accurate battery aging data: Resets the system so it doesn’t treat a new battery as an old, degraded one.
• Electrical reliability: Reduces the likelihood of voltage-related errors, warning lights, or erratic behavior.
• Preservation of accessories: Helps maintain stable voltage for sensitive modules, including audio, comfort, and safety systems.

Skipping registration may not cause immediate failure, but it often shortens battery life and can lead to unpredictable electrical issues over time, especially in a vehicle as electronically complex as the E90 3 Series.

Matching Capacity When Registering

Because the system expects a certain amp-hour rating, replacing an 80Ah battery with a 90Ah unit—or switching between AGM and flooded—should be reflected in the coding or registration parameters if your shop has the right tools.

The following points outline how to manage capacity changes correctly during battery replacement.

• Same size swap (e.g., 80Ah AGM to 80Ah AGM): Register as a new battery with the same capacity and type.
• Capacity increase (e.g., 80Ah to 90Ah): Use BMW-compatible software (ISTA, Autologic, or capable aftermarket scan tools) to set the new capacity.
• Type change (flooded to AGM): Ensure the system is updated to AGM so charging voltage and strategy match the new technology.
• Professional assistance: If you lack coding tools, most BMW-specialist shops can perform registration in a short service visit.

Correctly registering the battery to match its actual capacity and type maximizes both performance and longevity, making your investment in a proper 94R AGM battery more worthwhile.

Practical Buying Tips for a Replacement Battery

With the size and technical needs understood, the remaining questions involve brand, specifications, and what to ask for at the parts counter or online.

What to Look for When Purchasing

Not every 12V battery that fits the general dimensions will be ideal for your BMW, so it pays to verify a few core details before you buy.

The following checklist outlines the main criteria you should confirm when choosing a replacement battery for a 2011 328i.

• Correct group size: Ensure it is explicitly labeled as Group 94R (or H7) to fit the tray and terminals.
• AGM designation: Prefer AGM technology; confirm “AGM” or equivalent on the packaging or spec sheet.
• Amp-hour rating: Aim for 80–90Ah, matching or slightly exceeding the factory rating without going to an extreme.
• Cold cranking amps: Look for at least ~720 CCA; more is fine as long as the Ah rating is in range.
• Warranty and brand reputation: Choose a reputable brand with a solid replacement warranty and BMW-compatible specs.
• Vent provisions: Verify the case has a vent port and that you can connect the existing vent tube in the trunk.

By checking these specifications, you reduce the risk of fitment problems or electrical incompatibility and improve the likelihood of a trouble-free ownership period after installation.

Summary

The 2011 BMW 328i is designed to use a Group 94R (H7) 12-volt battery, typically an 80–90Ah unit with roughly 720–900 CCA, mounted in the trunk on the right side. While some cars left the factory with conventional flooded batteries, an AGM 94R is now widely recommended for durability and safety. Confirm the existing battery’s label and cross-check with your VIN or OEM catalog to ensure you match both size and capacity. After installation, the new battery should be properly registered to the car’s electrical system so the charging profile and battery monitoring are correctly calibrated, helping to prevent premature failure and electrical issues.