Start-stop systems in the workshop
Article supplied by Bosch
Bosch start/stop technology can be found in more and more passenger cars, and by 2017, 90 percent of all new vehicles will be fitted with startstop systems. There will thus be a significant demand from workshops for the corresponding parts required for professional replacement.
The function of a start-stop system, i.e, a system that automatically starts and stops the engine, requires the collaboration of a number of different components.
The number of starting sequences that are carried out with the starter motor, i.e, its service life, has been considerably increased so that the starter motor is able to withstand the frequent starts made over the lifetime of the vehicle.
The following measures have thus been implemented: Strengthening of the bearings
which come under severe strain. Further improvement of the
planetary gear. Use of a stronger starter pinion
drive. Optimisation of the commutator for
longer service life. “Efficiency Line“generators for start-stop systems create more electrical energy for the on-board diagnostics, even at low speeds and directly after the vehicle has been started. Together with the highperformance battery, they increase the availability of the startstop function. Improved electrical design and
optimised materials. Particularly efficient at low speeds. High efficiency diode technology
(HED): Greater efficiency of up to 77
percent. Greater fuel savings of up to two
percent. Noise-optimised.
The electronic control unit is fitted with additional interfaces for starters and sensors (battery sensor, crank shaft sensor, wheel speed sensor, neutral gear sensor). The software is capable of analyzing relevant data transmitted by the sensors. The control unit signals when the engine can be switched off.
The sensors deliver information to the control unit for optimisation of the starting sequence Neutral gear sensor: shows whether
the vehicle is in gear. Wheel speed sensor: shows the direction in which the wheel is rotating and when it comes to a stop. Intelligent crank shaft sensor
reports on engine activity. The differential pressure sensor for the brake booster monitors the pressure in the brake booster during the stop phase to ensure booster performance after starting. When actuating the starter, the voltage level of the on-board diagnostics decreases at short notice. This can have an impact on the function of the electronic devices (e.g. the radio reception is briefly interrupted or the navigation system switches off). DC-DC converters for start-stop system stabilise the voltage for parts of the electronic on-board diagnostics when starting the engine so that there is no interference with the comfort functions.
The engine control unit with the integrated start-stop coordinator and the battery sensor are the most important components of the energy management system for vehicles with a start-stop system. Also included here are the cycle-proof battery with EFB or AGM technology and the DCDC converter.
The EBS electronic battery sensor is one of the main components of the electronic energy management: Built into the battery terminal. It records, accurately and dynamically, operating data such as electricity, voltage and temperature. With the measured values, it monitors the performance of the battery and determines energy consumption and emission. High-performance and cycle-proof batteries are required for start-stop systems. AGM (Absorbent Glass Mat) batteries or EFB (Enhanced Flooded Battery) batteries are thus used. For systems with recuperation (regenerative braking), AGM batteries are used.
AGM batteries
Best available technology. Up to four times higher deep-cycle resistance in comparison with standard starter batteries. Superb charge acceptance. Operational even at very low charge
states. Superb cold start performance. Acid is completely bound in
microfibre mats. Can be installed anywhere, secured 100 percent against leaks and tilting. Absolutely maintenance-free. Original equipment quality.
EFB batteries
Double deep-cycle resistance in comparison with conventional starter batteries. Improved charge acceptance. With additional polyester scrim
between plate and separator. Greater density of active mass for
better flow of current. Secured against leaks and tilting up
to 55 degrees. Absolutely maintenance-free. Original equipment quality. It is not recommended that motorists change the batteries themselves in vehicles with start-stop systems as many of these vehicles (e.g. Audi, BMW, Volvo) require a suitable control unit diagnostics tester. The following are then possible: Breaking in the new battery in
the vehicle. Programming of technical data, e.g. amp hour and product number. The vehicle manufacturers take different approaches to breaking in the battery. The ESI[tronic] workshop information software should thus be consulted on a case by case basis.
It is important to take note of which new batteries are fitted. Only those batteries approved by the manufacturer should be selected and, as a general rule, conventional lead acid batteries are not to be used.
An AGM battery may only be replaced by an AGM battery, however an EFB battery may be replaced by an EFB or an AGM battery. If the wrong type of battery is inserted, the start-stop system will not reach its full potential. The service life of the batteries will also be reduced.
A fully charged battery is all the more important during the colder periods for vehicles with start-stop systems. It is thus recommended that batteries are charged each time the vehicle is in the workshop.