Bosch has started manufacturing the electronic battery sensor (EBS) system to help avoid the most common cause of vehicle breakdowns - a discharged battery.

Using integrated evaluation electronics, the sensor measures the battery voltage, current and temperature, calculating from these all the information that establishes the condition of the battery.

The energy management system incorporated in newer cars uses these values to guarantee a sufficient and continuous level of battery energy, so that the vehicle can be started reliably even after a long stationary period.

In 2007, more vehicles equipped with the sensor will go into production but the supplier has not named them.

The battery sensor consists of a chip that contains the electronics, and a shunt for current measurement. These two components, along with the pole terminal, form a unit that can be connected directly to the car battery, fitting into the pole niche of standard automotive batteries. This yields a significant saving in both space and costs over previous methods.

Bosch has developed the software for battery state detection in collaboration with battery specialists Varta. The algorithms are fully integrated into the EBS chip and the sensor directly measures the battery temperature, voltage and current, using these to calculate the capacity, state of charge and the current performance expected from the battery.

It supplies this information via an LIN interface to the vehicle's energy management system, which can use this data to optimise the state of charge.

If, over a relatively long period of time, more electric charge is used than the alternator can provide, the level of charge in the battery will fall. The energy management system compensates for this before a critical battery state is reached by reducing the power consumption of comfort items such as seat heating, and may even switch them off altogether for short periods.

It can also increase the engine's idle speed, and therefore alternator speed, if the vehicle is stuck in a traffic jam for a longer period. Even if a large number of electrical consumers draw on the battery on the vehicle's previous journey, or if the vehicle has been left standing for a considerable period, the battery's state of charge is improved, which means that the period in which a vehicle can be re-started reliably is now much longer.

Apart from the present state of charge, the software can also forecast the future charging condition of the battery. In addition, it is possible to control power generation by the alternator more precisely, reducing fuel consumption and therefore emissions.

Accurate information about the battery is also needed in vehicles with stop-start systems. For example, the engine will only be switched off if there is sufficient power available to restart it subsequently without any difficulty.

Additional benefits offered by the sensor include greater diagnostic possibilities for repair technicians.

During the vehicle manufacturing process, a quiescent current test can be carried out, allowing any problems to be detected in advance.