Performance of the energy recovery system of the BMW Series 1

The principle of energy recovery is based on fuel economy during engine start up and a reduction in polluting emissions from the exhaust gases. In this way, according to the driving profile, we can save up to 3% of CO2 and thus save energy.

This system is applied to the intelligent regulation control system of the alternator, also known as the IGR system by BMW.

Operating principles

Operating principles

The application of strategies in the battery charging regulation system which enables the battery to be charged only up to a defined measurement and depending on the different environmental conditions such as the outdoor temperature, the temperature inside the battery, the age of the battery, battery charge, etc.

In this way, the constant regulation of the system prevents energy being wasted while the engine is running without repercussions on the thermal efficiency of the latter.

Operating phases

Energy recovery is carried out during the vehicle's propulsion phases. At this time, the alternator is fully activated and generates the electrical energy that supplies the battery. Once the vehicle is launched, it does not consume fuel as the kinetic energy acts from the vehicle under propulsion to the alternator passing through the wheels and engine.

However, during the acceleration phases of the vehicle the alternator is not activated, therefore it does not use any power or fuel to produce electrical energy.

With Intelligent Alternator Control (IGR), energy recovery is achieved that translates into a reduction in fuel consumption.

The IGR function software is integrated into the engine control unit (DME). Communication between the engine control system, the intelligent battery sensor and the alternator is via the CAN-Bus data interface. The state of charge and aging of the battery is calculated by the Power Management system with the information received from the intelligent battery sensor.

The Power Management software carries out the calculations for energy management. It is integrated into the engine control unit (DME). In vehicles with intelligent alternator control, the Power Management system takes on the alternator control processes.

The intelligent alternator control (IGR) function comprises three vehicle speed levels:

IGR low

AGM Battery

The vehicle is in the propulsion phase, electrical energy is supplied to the battery.

The alternator voltage is raised during the vehicle's propulsion phases, it is only activated above 1000 rpm and 10 km/h. During these propulsion phases, the IGR system increases the alternator voltage which makes it possible to increase the battery charge. In this phase, the state of charge of the battery can reach 100%.

IGR high

IGR high

IGR mid

When the state of charge of the battery has reached a sufficiently high level, its discharging is prevented, and the alternator supplies the energy necessary for electrical consumption.

The battery does not charge actively now, and maintains a state of charge at a sufficient level between 70% and 80%, to discharge again in a controlled way. A partial or full discharge request is required of the alternator in case of a low power supply requirement of the onboard power supply with the automatic control in order to reduce fuel consumption.

The alternator intelligent control takes place when a set minimum battery charge is reached. When the charge is sufficient, the alternator voltage is regulated in such a way that the charge will remain constant outside the propulsion phases. In this state, the alternator will only supply voltage to the onboard power supply.

IGR high

When the vehicle accelerates, the battery supplies the energy to operate the electrical load. 

When the battery charge is high, the alternator voltage is regulated in such a way that the battery will discharge to an acceptable level. The battery will partially supply voltage to the onboard power supply, and the alternator will only have a stabiliser effect on the onboard power supply. The Power Management system limits the desired voltage level of the IGR system to an acceptable on-board power supply voltage.

IGR high

IGR high 

This recovery system applied to vehicles nowadays has a number of advantages and differences for the customer and environment:

IMPORTANT NOTE: The intelligent alternator regulation should be disabled when inspecting the alternator using the BMW diagnostics system.