BSG, belt starter generator

The BSG or Belt Starter Generator it is a device capable of performing two functions, generate current or driving torque. It replaces the classic alternator in some cars with combustion engines that adopt new hybridization solutions, the so-called “mild hybrid (MHEV)” which combine the internal combustion engine with an electric motor to improve efficiency and reduce emissions. Its dimensions are slightly larger than the classic alternator especially for 48V BSGs.
The one in the photo is mounted on the Stellantis thermal unit, the Puretech 1,200 3-cylinder turbo that we find on the Jeep Avenger, Renegade and Compass. Mild-hybrid cars equipped only with BSG are not capable of driving in all-electric mode for short distances. In the specific case of Avenger, Renegade And Compass this is made possible by a second electric motor more powerful 21 kW keyed to the gearbox and managed with a double clutch.

The electronics that manage the BSG are usually very advanced and are also able to ensure the “soaring” of the motor itself or reduce the load to zero, interrupting the generation of current when not necessary.

The functions of the BSG:

• Starting the engine: The BSG can start the petrol engine silently and quickly, without using the traditional starter motor which may no longer be present.
• Braking energy recovery: During braking, the BSG converts kinetic energy into electrical energy, which is stored in a 12 or 48V battery.
• Engine assistance: the BSG can provide an electric boost to the petrol engine during acceleration, improving performance and reducing consumption. It assists the engine during acceleration while traveling at a constant speed (for example on the motorway), reducing fuel consumption.
• Generator: when necessary, the BSG generates current through the torque provided by the combustion engine to power the car's 12V electrical system to which all the auxiliary systems are connected, such as air conditioning, electric power steering, electric parking brake, l multimedia system, lights, etc.

Benefits of BSG:

• Reduction in fuel consumption: BSG can reduce fuel consumption by 5-10%, depending on vehicle type and driving cycle.
• Reduction of emissions: slightly reduces emissions of CO2 and other pollutants.
• Better silence: starting the petrol engine through the BSG is quieter both during the first ignition and during Start&Stop when the thermal switch is turned off and on continuously in congested traffic situations and when stopping at traffic lights.
• Reduced engine wear: by supporting the engine in the acceleration and recovery phase, it also guarantees less wear on the components of the internal combustion engine itself.

BSG at 12 and 48Vare two types that differ in working voltage:

• 12V BSG less powerful and less widespread than 48V BSGs.
• BSG at 48V: they are more powerful and offer greater benefits in terms of consumption and emissions. In this case the starter-generator is combined with a DC/DC converter to connect and balance the 12V and 48V networks. Furthermore, a second 48V battery is added to store more energy with which to allow fully electric driving (but also all-wheel drive).