The battery is a 12-volt unit, and the common replacement size for a 2008 BMW 335i is Group 48 (H6) with about 90 amp-hours (Ah). Exact specs can vary by market and options, so check the battery label or the owner's manual to confirm.
Battery size and specifications
To understand what to buy, review the typical characteristics of the OEM battery used in most 2008 335i models.
- Battery group size: Group 48 (also labeled H6)
- Voltage: 12 volts
- Capacity: typically around 90 Ah (ranges can be 80–90 Ah depending on exact spec)
- Type: Flooded lead-acid is common; some cars with higher electrical demand or optional Start-Stop may use an AGM variant
- Cold-cranking amps (CCA): generally in the 700–800 A range for standard flooded batteries; AGM variants can be higher (roughly 750–900 A)
- Location: trunk-mounted battery (usually on the left side) with a harness feeding the engine bay
In practice, the baseline specification to look for is a Group 48/H6 battery around 90 Ah. Always verify the exact rating on the battery label or by checking the vehicle’s documentation.
Where is the battery located and how to replace
Knowing the location and steps helps ensure a safe and successful replacement if you’re doing it yourself.
- Prepare the vehicle: park on a level surface, engage the parking brake, and consider using a memory saver to protect radio and ECU settings.
- Open the trunk and remove the battery cover to access the battery mounting area.
- Disconnect the negative (ground) terminal first, then the positive terminal.
- Remove the battery hold-down clamp or strap and lift the battery out of the tray, taking care not to short the terminals.
- Clean the battery tray and terminals if needed; inspect the tray for corrosion and ensure a secure fit for the new battery.
- Install the new battery: place it in the tray, secure the hold-down, connect the positive terminal first, then the negative terminal.
- Reattach the trunk cover and reset any settings if you used a memory saver; start the car to verify proper operation and reset clocks or radio presets as needed.
If you have a vehicle with Start-Stop technology or other high-demand electrical systems, a premium AGM battery is often recommended to maintain performance and longevity. If you’re unsure about handling battery replacement, consider professional service to avoid electrical or memory issues.
Choosing the right replacement and maintenance tips
Guidance to help you select the correct battery and keep it in good condition.
- Match the group size: Group 48 (H6) for the 2008 335i, with a capacity around 90 Ah.
- Consider AGM if your car has Start-Stop or heavy electrical loads, as it handles frequent cycling better.
- Check the CCA rating to ensure it meets or exceeds OEM requirements; higher CCA is beneficial in cold climates.
- Buy from reputable brands (OE-equivalent or well-known aftermarket) and verify fitment using the exact vehicle year, model, and options.
- When installing, follow proper precautions to protect the vehicle’s electronics and avoid short circuits; store old battery safely for recycling.
Overall, the key is to replace with the correct Group 48/H6 12V battery (~90 Ah) and to choose AGM only if your specific vehicle requires or benefits from it due to Start-Stop or high electrical demand.
Summary
For a 2008 BMW 335i, the standard battery size is a 12-volt Group 48 (H6) unit, typically around 90 Ah. Verify the exact specification on the battery label or in the owner’s manual, and choose an AGM variant only if your car has Start-Stop or other high-electrical-demand features. The battery is usually located in the trunk, left side, and replacement involves careful disconnection and reconnection of terminals, proper mounting, and reassembly of the trunk area.