What Kind of Battery Does a 2008 BMW 335xi Take?

The 2008 BMW 335xi typically uses a Group 49/H8 AGM (Absorbent Glass Mat) 12‑volt battery, around 90–95 Ah and 850+ CCA, installed in the trunk and requiring electronic registration after replacement. While some cars came with a flooded lead‑acid battery, BMW and most experts now recommend an AGM unit that matches the original capacity and specifications.

Understanding the 2008 BMW 335xi Battery Specification

The 2008 BMW 335xi (E90 chassis, all‑wheel drive, 3.0L twin‑turbo N54 engine) is relatively demanding on its electrical system. Between the electric water pump, fuel system, extensive sensors, and comfort electronics, the battery must meet strict size, power, and technology requirements to function correctly with BMW’s intelligent charging system.

Battery Group Size and Physical Fitment

BMW uses standardized “group sizes” to ensure batteries fit securely in the vehicle’s designated compartment. For the 2008 335xi sedan, the most common and correct physical size is Group 49, which is also often labeled as H8 in European sizing.

The key fitment characteristics for the 2008 BMW 335xi battery are summarized below.

• BCI Group Size: Group 49 (commonly cross‑listed as H8)
• Location: Trunk, right side (under trim panel, near the wheel well)
• Polarity: Standard “left‑positive” layout (matches OEM cables)
• Dimensions: Approximately 15 x 7 x 7.5 inches (38 x 17.5 x 19 cm), varying slightly by brand
• Hold‑Down Style: Bottom‑flange mount compatible with BMW bracket

Using the correct group size ensures the battery sits firmly in the factory tray, the terminals line up correctly, and the venting system can be properly connected, which is important for both safety and longevity.

AGM vs. Conventional Lead‑Acid: What BMW Intended

Some 2008 BMW 3 Series models left the factory with conventional flooded lead‑acid batteries, while others were equipped with AGM units, especially on higher‑option cars and colder‑climate specs. However, BMW and most professional technicians now lean strongly toward AGM batteries on these E90‑generation cars because of their electrical demands and charging strategy.

The following list highlights the main differences and reasons why AGM is preferred in a 2008 335xi.

• AGM Technology: Designed to handle frequent charge/discharge cycles and higher electrical loads.
• Vibration Resistance: Better internal construction for rough roads and spirited driving.
• Spill‑Resistant: Sealed design with a vent, safer in the trunk and passenger compartment area.
• Cold‑Weather Performance: Typically higher CCA (cold cranking amps) and stronger starting in winter.
• Compatibility with BMW Charging: Matches the strategy used by BMW’s Intelligent Battery Sensor (IBS) and alternator control.

While a conventional flooded battery can physically fit and may be cheaper, an AGM unit better matches the car’s electrical architecture and is more likely to deliver stable performance and longer service life.

Key Electrical Specifications: Ah, CCA, and Type

Beyond physical size and chemistry, the 2008 BMW 335xi’s battery must meet certain power and capacity standards to work correctly with the engine and electronics. The factory specification is usually printed on the original battery label, but many OEM units have long since been replaced, so it is important to know the general requirements.

Typical OEM‑Equivalent Specs

Most reputable fitment guides and BMW‑focused shops recommend a battery with the following specifications for the 2008 335xi:

The list below outlines the typical electrical targets you should look for when buying a replacement battery.

• Voltage: 12 V (standard for passenger vehicles)
• Battery Type: AGM (Absorbent Glass Mat) strongly recommended
• Capacity (Ah): Typically 90–95 Ah for OEM‑equivalent fitment
• Cold Cranking Amps (CCA): Roughly 850–900+ CCA, depending on brand
• Reserve Capacity (RC): Generally in the 160–170 minute range (not always listed on BMW labels, but available on aftermarket spec sheets)

Staying close to the original amp‑hour rating is important because BMW’s charging system is calibrated to battery capacity. A big deviation—especially without proper re‑coding—can lead to under‑charging or over‑charging and premature battery failure.

Common Aftermarket Battery Options

Many mainstream brands sell Group 49/H8 AGM batteries that meet or exceed BMW’s needs. Exact product lines change over time, but major retailers and auto‑parts chains in North America and Europe routinely stock units specifically cataloged for the 2008 335xi.

The following bullet points describe the types of products you will typically see marketed for this car, rather than endorsing any specific brand.

• Premium AGM Lines: Labeled as “AGM,” “Platinum AGM,” or “Ultra AGM,” often with 90–95 Ah and 850+ CCA.
• OEM‑Label Batteries: Batteries sold through BMW dealers that are pre‑coded for BMW applications but still require registration.
• European‑Spec H8/95Ah Units: Often branded with 95 Ah capacity and high CCA, specifically matching German‑car specs.
• Batteries with IBS Compatibility: Not a special connector, but marketing language noting suitability for vehicles with intelligent battery sensors and start‑stop–like charging logic.

When purchasing, matching Group 49/H8, AGM type, and a capacity around 90–95 Ah will generally ensure proper compatibility, even if brand names and exact model numbers differ by region and retailer.

Location, Venting, and Safety Considerations

Because the 2008 BMW 335xi’s battery is mounted in the trunk rather than under the hood, there are additional installation and safety factors to consider, particularly regarding venting and secure mounting.

Battery Location and Access

The battery is located on the right side of the trunk, under the carpeting and trim. Accessing it usually requires removing a side panel, lifting a cover, and sometimes removing a plastic tray or bracket. The positive terminal under the hood is for jump‑starting or external charging; it is not where the battery itself sits.

The points below describe practical aspects of the 335xi battery location and what that means for replacement.

• Trunk‑Mounted: Keeps the battery away from engine heat, aiding longevity.
• Weight Distribution: Part of BMW’s effort to balance chassis weight front‑to‑rear.
• Interior Space: Requires removal of trunk trim panels to access the battery.
• Remote Jump Posts: Dedicated jump‑start terminals under the hood for convenience and safety.

Knowing that the battery is in the trunk helps owners avoid confusion when they see only terminals in the engine bay and may influence their decision to do a DIY replacement or seek professional help.

Venting Requirements

Even with AGM technology, batteries can release small amounts of gas during charging. BMW therefore uses a vent tube connected to the battery, directing any gases safely outside the car. Many generic batteries are sold with a vent port but not the correct fittings for BMW’s tube.

The list below covers key venting details to check when choosing and installing a battery.

• Vent Port: The replacement battery must have a vent port compatible with a side vent tube.
• Vent Tube Connection: The plastic tube in the BMW trunk must be firmly attached to the new battery’s port.
• Sealing Unused Ports: If the battery has two vent ports, the unused side must be plugged (often supplied with the battery).
• No Operation Without Vent: Do not run the vehicle for long periods with the vent tube disconnected or missing.

Correct venting is an important safety measure, reducing moisture and potential gas accumulation in the trunk and rear cabin area over time.

Battery Registration and Coding in a 2008 BMW 335xi

Unlike many older cars, the 2008 BMW 335xi requires an electronic “battery registration” process after installation of a new battery, and in some cases a change of battery type or capacity also calls for coding. This is a key detail many non‑BMW owners are unaware of.

Why Battery Registration Matters

BMW uses an Intelligent Battery Sensor (IBS) and an electronic control module to manage charging, adjust alternator output, and track battery age and condition. Installing a new battery without telling the system can cause suboptimal charging and reduced lifespan.

The following points summarize the role of registration and coding in a 2008 335xi.

• Resets Battery Age: Registration informs the car that a new battery is installed, resetting internal aging models.
• Adjusts Charging Strategy: Ensures charge voltage and current are matched to a fresh battery rather than an older one.
• Prevents Over‑ or Under‑Charging: Reduces the risk of premature failure of even a high‑quality AGM unit.
• Coding for Different Specs: If changing from flooded to AGM or changing Ah rating significantly, coding must be updated in the vehicle software.

Skipping registration does not usually cause an immediate failure, but it can noticeably shorten the life of a new battery and contribute to intermittent electrical issues.

How Registration Is Performed

Battery registration on an E90 like the 2008 335xi is done via specialized diagnostic software rather than through any button sequence in the cabin. Owners can either go to a dealer/independent BMW shop or use their own compatible tools.

The steps and options below give a high‑level view of how registration typically happens.

• Dealer Service: BMW dealers use factory tools (ISTA, etc.) to register and, if needed, code the battery.
• Independent BMW Shops: Many independent specialists have equivalent or aftermarket software that can handle registration.
• DIY Scan Tools: Certain consumer‑level scan tools and phone‑app dongles support BMW battery registration for E90 models.
• Information Needed: The technician needs to know battery type (AGM vs flooded) and Ah rating to code correctly if different from the original.

Because registration is typically quick, many shops bundle it with the battery replacement. DIY owners often choose AGM with the same capacity as the old battery to minimize the need for coding changes, though registration is still recommended.

How to Confirm the Correct Battery for Your Specific 335xi

The specifications above apply broadly to the 2008 BMW 335xi, but some variation exists based on market, trim level, and original equipment. Verifying what your individual car expects is a good way to avoid mismatches.

Steps to Double‑Check Compatibility

Before purchasing a replacement battery, you can take a few simple steps to confirm that Group 49/H8 AGM around 90–95 Ah is correct for your exact vehicle.

The checklist below outlines practical verification methods.

• Look at the Existing Battery Label: Identify group size, Ah rating, and whether it says AGM or similar wording.
• Check the Trunk Sticker: Some cars have a label near the battery with original spec information.
• Use VIN‑Based Parts Lookup: Online BMW parts catalogs or dealer systems can show the original battery spec by VIN.
• Consult Reputable Retailers: Use major auto‑parts stores’ online fitment tools, then cross‑check group size and AGM type.

By confirming the original configuration and matching it closely, you improve the chances of a trouble‑free installation and electrical performance that stays consistent with BMW’s design.

Summary

The 2008 BMW 335xi is engineered to use a trunk‑mounted, Group 49/H8 12‑volt battery, and the most appropriate modern replacement is an AGM unit with roughly 90–95 Ah capacity and around 850 or more cold cranking amps. While some cars originally carried flooded lead‑acid units, BMW’s charging strategy and the electrical demands of the E90 platform make AGM the sensible choice today. Ensuring proper fitment, connecting the vent tube, and performing electronic battery registration—and coding if the type or capacity changes—are all critical steps to keeping the 335xi’s electrical system healthy and its starting performance reliable.

What type of battery does the BMW ix use?

The BMW iX uses a lithium-ion battery with a Nickel-Manganese-Cobalt (NMC) chemistry. Different models have varying total and usable capacities, such as the iX M60 with a 111.5 kWh gross capacity (105.2 kWh usable). The iX features a 400-volt system and includes thermal management with a heat pump for efficient charging and operation.
 
This video discusses a prototype dual-chemistry battery for the BMW iX: 59sGlobal UpdateYouTube · Dec 11, 2023

• Battery type: Lithium-ion with Nickel-Manganese-Cobalt (NMC) chemistry. 
• Battery capacity: Varies by model, for example, the iX M60 has a gross capacity of 111.5 kWh and a usable capacity of 105.2 kWh. 
• Architecture: 400-volt system. 
• Thermal management: Includes a liquid cooling system and a heat pump for pre-conditioning, heating, and cooling. 
• Charging: Supports DC fast charging up to 150 kW for the xDrive40 and 200 kW for the xDrive50, and home charging via an 11 kW AC charger. 

What kind of battery does a BMW 335i take?

DieHard Platinum AGM – Battery: H6 Group Size, 4 Year Warranty, 760 CCA, 950 CA, 120 Minute Reserve Capacity (Part No. H6-AGM)

What kind of battery does a 2008 BMW 335i take?

H6 Battery
Duralast Group Size 48 H6 Battery H6-DL.

What size battery is in the 2008 BMW 535xi?

The 2008 BMW 535xi battery size is typically a Group 48 (H6) or 94R (H7), though some sources also mention Group 49 (H8) or 95R as potential fits. It is important to verify the correct size by checking the battery currently in your vehicle and ensuring the new battery has the appropriate cold cranking amps (CCA) and reserve capacity. 
Common battery sizes

• Group 48 (H6): A common and often correct fit for the 2008 535xi. 
• Group 94R (H7): Another frequently recommended size that is compatible with the vehicle. 
• Group 49 (H8): Some retailers list this as an option for the 2008 535xi. 
• Group 95R: Mentioned as another compatible size, though some sources suggest potential fitment issues or the need for a specific type. 

Important considerations

• Verify your current battery: The most reliable way to ensure the correct size is to check the label on the battery currently installed in your car. 
• Check CCA: Make sure the new battery meets or exceeds your vehicle’s original cold cranking amps (CCA) specifications. 
• Reset vehicle computer: Some modern BMWs require the vehicle’s computer to be reset by a service specialist after a battery replacement to ensure proper function.