The C300’s battery setup depends on the drivetrain: a 12V auxiliary battery powers standard electronics, and newer models add a larger high‑voltage or 48V pack in mild-hybrid or plug-in variants. Exact capacities vary by model year and market.
Battery configurations by C-Class variant
12-volt auxiliary battery
Here are typical specs for the 12V battery used in standard C300 models that are not plug-in hybrids.
- Type: AGM (absorbent glass mat) lead‑acid battery
- Capacity: typically around 70–80 Ah
- Voltage: 12 V
- Location: mounted in the engine bay or a dedicated compartment, depending on year and market
- Replacement interval: generally about 3–5 years, depending on climate and use
- Notes: charged by the alternator and monitored by the vehicle’s battery management system
When replacing a 12V battery, it’s important to match the vehicle’s specifications to avoid electrical issues or fault codes.
48-volt mild-hybrid battery (MHEV)
For C300 models equipped with mild-hybrid technology, a compact 48V battery supports the integrated starter and electrical systems.
- Type: lithium‑ion, part of the 48V mild-hybrid system
- Capacity: roughly 0.5–1.0 kWh (500–1000 Wh)
- Voltage: 48 V
- Location: a compact pack typically located in a rear/underfloor area or near the drivetrain, integrated with the 48V system
- Purpose: assists with start/stop, torque augmentation, and energy recovery
- Service: usually not user-serviceable; module replacement by MB if needed
The 48V system helps improve efficiency and smooths engine off/on transitions, but the exact capacity can vary by model year and market.
Plug-in hybrid high‑voltage battery (C300e)
In the C300e plug‑in hybrid variant, there is a much larger high‑voltage pack used for electric driving.
- Capacity: around 15.6 kWh gross (roughly 13.5 kWh usable in many versions)
- Voltage: approximately 350–400 V (high‑voltage system)
- Location: typically the battery pack is mounted in the vehicle’s floor area, often spanning under the rear seating or trunk region
- Electric range: varies by year and testing cycle, generally tens of kilometers on electric power alone per charge
- Charging: supports external charging (AC), with performance depending on the onboard charger and market standards
- Notes: significantly larger than the 12V/48V packs and intended for extended electric driving
Exact specs for the C300e can differ by model year and market; always verify with the VIN or official Mercedes documentation for your car.
How to verify the exact battery for your car
To confirm the precise battery size for your specific C300, use these steps to cross-check documentation and labels.
- Check the owner’s manual or the maintenance booklet for battery specifications by drivetrain
- Inspect the battery label under the hood for capacity and type information
- Look up the VIN on Mercedes’ official service portal to retrieve the original equipment specifications
- Consult a Mercedes-Benz dealer or qualified technician for model-year-specific data
Knowing the exact battery type and capacity helps with replacements, charging expectations, and ensuring you use compatible equipment.
Summary
The Mercedes-Benz C300 uses a standard 12V auxiliary battery across most non-plug-in models (about 70–80 Ah), and, in modern variants, a 48V mild-hybrid pack (roughly 0.5–1 kWh). The plug-in hybrid C300e carries a much larger high‑voltage battery, typically around 15.6 kWh gross (about 13.5 kWh usable), enabling electric driving for longer ranges. Exact figures depend on model year, market, and drivetrain, so verify with official documentation or your dealership for precise specifications.