The 2008 Mercedes-Benz R350 typically has a single 12-volt battery. There is no standard second battery in the stock configuration.
Understanding the standard battery setup
The R350 relies on one 12-volt lead-acid battery to power starting, lighting, and accessories. It does not come with a high-voltage traction battery, as the model is not a hybrid. Some owners or markets may use an auxiliary battery or aftermarket solutions for additional electronics, but these are not part of the original equipment.
Notes on placement and battery type
In many examples, the 12-volt battery is located in the engine bay. Depending on production date and market, some vehicles may place the battery in the luggage compartment or behind trim panels. The battery type may be a conventional lead-acid or an AGM variant, chosen by Mercedes for reliability and, in some cases, compatibility with start-stop technology. For precise configuration, consult the owner's manual or VIN-specific documentation.
How to verify for your car
To confirm how many batteries your exact R350 has, check the battery label under the hood for its type and capacity, inspect the trunk or rear area for any additional modular battery housing, or contact a Mercedes-Benz dealer with your VIN.
Summary
In short: expect one 12-volt battery in a 2008 R350, with possible variations by market or aftermarket modifications. Always verify using official documentation for your specific vehicle.