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AGM, EFB, and BMS: What Matters When Replacing a Battery

Battery Replacement – With Modern Cars, the Right Technique Is Key.(Bild: Banner)

Just take out the old battery and put in a new one? With modern cars, changing the battery is more complicated. Start-stop technology, AGM and EFB batteries, and battery energy management require special attention. Following a few important rules ensures a reliable start and optimal power supply to the vehicle’s electrical system.

When replacing a battery, the first consideration is choosing the right technology. Banner recommends using a battery with the same case and a similar performance class whenever possible. This is particularly important for vehicles with a start-stop function: If an EFB or AGM battery was installed at the factory, it must under no circumstances be replaced with a conventional wet-cell battery.

Upgrading from EFB to AGM is also possible—but there are a few things to keep in mind. If the start-stop vehicle has a battery energy management system (BEM), the new battery must be programmed into the system. A battery sensor on the negative terminal may indicate a vehicle with a start-stop system and battery energy management.

Start-stop systems place particularly high demands on the car battery—so choosing the right technology is crucial.(Bild: Banner)

To preserve the settings
Replacing the battery can also affect the vehicle’s electronics. For example, some automakers disable the radio when the power supply is interrupted until the corresponding security code is entered. Banner therefore recommends an external power preservation solution, such as a Memory Saver connected via the OBD port. This ensures that vehicle settings and data are preserved during the replacement.

Important: While the external voltage is being maintained, avoid using additional power-consuming devices. Opening doors or the trunk, for example, can cause a significantly higher current flow and strain the auxiliary circuit’s fuse.

Negative First, Then Positive
Before removal, the engine and all electrical loads must be turned off. When disconnecting the terminals, follow a specific order: first disconnect the negative terminal, then the positive terminal. Next, loosen the battery mount and remove the old battery. Before installing the new battery, the mounting surface should also be cleaned.

Installation is done in exactly the reverse order: Securely mount the new battery, then connect the positive terminal first, followed by the negative terminal. The terminals and terminal clamps should be clean and can be lightly greased with acid-free grease. Take special care to ensure the terminal clamps are securely fastened.

Safety First
According to Banner, safety goggles and gloves are just as much a part of the recommended equipment as suitable tools. Short circuits caused by tools must be avoided at all costs. Anyone who does not have the necessary tools or equipment should refrain from attempting this and have the battery replacement performed by a specialist shop or a Banner sales partner.

Once everything is correctly installed, remove any external voltage maintenance device that may have been used. Next, perform a test start. If the engine starts without any problems and the electrical systems function as usual, the battery replacement is complete.

More information and detailed step-by-step instructions on how to properly replace a battery are available from Banner.