Bosch’s EBS integrates with a car battery’s pole for space savings (Photo: Bosch)

Feb. 23, 2007&#8212Bosch has begun manufacture of its Electronic Battery Sensor (EBS), which promises to help motorists avoid flat batteries, the most common cause of breakdowns. With its integrated evaluation electronics, the MEMS sensor determines the battery’s condition by measuring voltage, current, and temperature. The energy management system incorporated in modern cars uses these values to continuously guarantee sufficient 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 series production.

The Bosch battery sensor consists of a chip that contains all 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 solutions.

Bosch developed the associated software for battery-state detection in collaboration with Varta, and integrated the algorithms into the EBS chip. The sensor determines the battery’s capacity, state of charge, and expected performance, and sends this information via an LIN interface to the vehicle’s superordinate energy management system, which uses the data to optimize the state of charge.

If over a 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 the seat heating, and may even switch them off altogether for short periods. It can also increase the combustion engine’s idle speed, and thus the alternator speed, if the vehicle is stuck in a traffic jam for a longer period. This improves the battery’s state of charge, which means that the period in which a vehicle can be re-started reliably is now much longer, even if a large number of electrical consumers drew on the battery on the vehicle’s previous journey or if the vehicle has been left standing for a considerable period.

Besides the present state of charge, the software can also forecast the battery’s future charging condition. And, it will be possible to control power generation by the alternator more precisely. This promises to reduce fuel consumption, and thus also emissions of pollutants.

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. And even when the vehicle is being manufactured, a quiescent current test can be done, allowing any problems to be detected. The sensor opens up greater diagnostic possibilities for garages&#8212for example, when a customer is having recurring problems with a flat battery.