Replacement of modern batteries is now considerably more complex than it was 20 years ago with conventional wet batteries. Up to 28 different steps are now necessary. This is just one of the reasons why replacement should be carried out by a specialist workshop. We have summarized the most important points below.
The answer to this question used to be very simple: under the hood of course. Now things are completely different. If you open the hood of a modern car, you will often not find the battery. These days, only 58% of batteries are in the engine compartment. 40% are in the trunk and 2% are installed in the passenger compartment. For some models, seats may even need to be removed or carpets cut in order to access the battery. An extra airbag qualification is necessary to remove the seats, for which special training is required. This is another reason to have the replacement carried out by professionals.
In a car with Start-stop technology the battery must only be replaced with a type which has been approved by the car manufacturer and which meet all of the necessary requirements. Due to the more complex on-board network, replacing a start-stop battery takes longer than for a conventional starter battery in a simple vehicle.
Replacing a modern start-stop battery takes up to 28 steps – which greatly increases the time which is required.
A start-stop battery is a part of the on-board electronics and is linked to the vehicle electronics via the Battery Management System (BMS) and the battery sensor (EBS). The control unit detects the number of starts and the energy flow, monitors the state of charge and controls charging. When a start-stop battery is replaced, the energy management s system is programmed by the diagnostic device in the workshop.
Incorrect DIY replacement of a start-stop battery can cause malfunctions. A battery replacement which is not carried out correctly can cause restriction or even failure of the start-stop function, which can result in increased fuel consumption and restriction of the comfort functions. The experts in a workshop have been trained to handle current battery technology and are familiar with battery replacements. They also know that an AGM must always be replaced with an AGM and an EFB must at be replaced with an EFB or an AGM.
When an EFB or AGM is replaced, a specialist workshop takes a series of points into account, which guarantee that the battery functions properly later on. Because the car is temporarily without power during the battery replacement, important operating settings must be noted beforehand. Alternatively, a second battery can be connected to maintain the operating voltage.
After the new battery has been installed and connected, the automatic start-stop system may not function for several hours. In this case, the workshop will inform the driver of this and give them the appropriate instructions. Drivers should contact the workshop directly in case of any malfunctions or error messages which occur after a start-stop battery has been replaced. In most cases, these are temporary and are due to incomplete data processing. In some cases, the vehicle requires genuine driving data to complete the setup. Some vehicle control units have a self-learning function, so that some of the error messages disappear automatically. In the VARTA Partner Portal workshops can find details of the procedures for replacing the battery for an automatic start-stop system, as well as the time which is required and which batteries are available as replacements.
There are currently 4 systems on the market to "teach" the new start-stop battery.
As already mentioned, depending on the make of car and the functionality of the respective system (open or closed), modern vehicles with Battery Energy Management (BEM) may or may not require or recommend that the new battery be registered.
1. Self-learning system: The BEM has only a few pre-programmed battery options per car model stored in it, which are used as reference data. Following the replacement of a start-stop battery, the BEM compares the actual values of the new battery with the learning values stored in the BEM and learns which of the stored reference data matches the measured actual battery performance.
The following car manufacturers work with self-learning systems: e.g. Abarth, Alfa Romeo, BMW, Chevrolet-Daewoo, Citroen, Dacia, Fiat, Honda, Lancia, Mercedes, Mitsubishi, Peugeot, Renault, Subaru, Suzuki, Toyota and Volvo.
2. Closed system - New registration with a diagnostic tool: Registration of the new start-stop battery in BEM, using a diagnostic device, is recommended or partially required here.
The following car manufacturers recommend or require a new registration: e.g. Alpina, Audi, BMW, Jaguar, Jeep, Land Rover, Mazda, Mini, Seat, Skoda and Volkswagen.
In addition, some of the aforementioned car manufacturers require a special BEM code to register the new battery during the change process for all or a number of certain car models, e.g. the VW Group for Audi. BEM codes always have two lines and are manufacturer and battery specific. One line usually notes the OE spare part number, often an alphanumerical part number for the OEM and OES sales channel. The second line notes the coding of the battery manufacturer, the production date of the battery and a specific number.
OE = Original Equipment, (OEM = ... Manufacturer, OES = ... Supplier)
Such a BEM code is not available for replacement batteries from the free parts market!
Depending on the diagnostic tool being used, some require a BEM code when changing the battery. In this case, it may be necessary to enter both lines for the BEM code of the new start-stop battery.
Other diagnostic tools generate the required battery-specific information themselves. In this case, it may not be necessary to enter the BEM code. Usually, you only have to select the battery capacity, battery manufacturer and battery technology used from a drop-down menu. The Volkswagen Group is currently able to enter any 10-digit serial number. The VW serial number is used for tracking the battery and for warranty purposes.
3. System combining 1. and 2.: This combined approach is available at a third group of passenger car manufacturers, depending on the model.
Used by the following car manufacturers: Ford, Hyundai, Kia, Lexus, Nissan, Opel, Porsche, Smart and Vauxhall.
4. Special case Ford (DE and USA): On some Ford models, it is possible to perform a BEM battery reset entirely without a diagnostic device. All you need to do is “simply” press different button and switch combinations.
4.1 Car WITH rear fog light: the steps have to be completed within 10 seconds.
4.2. Car WITHOUT rear fog light: the steps have to be completed within 10 seconds.
The BEM calibrates itself once the car has been locked for 3 hours.