This video provides a comprehensive, step-by-step DIY guide for replacing the 12-volt auxiliary battery in a 2017 BMW i3. The tutorial details the entire process from preparation, emphasizing the necessity of fully pre-charging the new battery, to the final software registration. Key steps include removing the front storage compartment, safely disconnecting the main high-voltage battery (a critical procedure for EVs), and removing the old 12V battery. The installation process is shown in detail, with a pro-tip on checking all terminal connections for tightness to prevent future electrical faults. The guide concludes by demonstrating how to register the new battery with the vehicle's computer using an iCar OBD-II adapter and the BimmerLink smartphone app, a vital step for ensuring proper charging and extending the battery's lifespan.
DIY Guide: Replacing the 12V Battery in a BMW i3
0:00:26 Preparation is Key: Before starting the installation, the new 12-volt battery must be fully charged. In this case, a Remy AUX 18L battery took 36 hours on a trickle charger to reach a full charge.
0:01:02 Accessing the Battery: The process begins by removing the front storage bucket ("frunk"). This requires removing six 4mm hex head bolts.
0:02:03 Critical Safety Step: Unlike gasoline cars, you must disconnect the high-voltage battery before working. The video shows the disconnect mechanism for both pre-2021 (orange lever) and 2021 (red clip) models. A pin or hex key should be inserted to prevent accidental reconnection.
0:03:01 Battery Removal: Using a 10mm socket with an extension, remove the metal bracket holding the 12V battery in place. Disconnect the negative terminal first, followed by the positive terminal.
0:05:20 Pro-Tip for Access: Temporarily removing the windshield washer fluid filler tube provides significantly more room to access and work on the battery terminals.
0:06:08 Vent Tube: BMWs use a vent tube to safely route battery gases outside the vehicle since the battery is in an enclosed space. This must be disconnected from the old battery and reconnected to the new one.
0:10:02 Check All Connections: Upon installation, ensure the new battery's brass terminal adapters are tight, along with the two 10mm nuts on the positive terminal assembly. A loose connection can cause random electrical faults.
0:14:14 Final Step - Battery Registration: After the physical installation is complete and the high-voltage system is reconnected, the new battery must be registered with the car's computer. This is crucial for optimizing charging cycles and ensuring the longevity of the new battery.
0:15:15 How to Register: The video demonstrates using an iCar OBD-II adapter plugged in under the dash, which connects to the BimmerLink smartphone app. The app has a simple function to "Register new battery."
0:16:43 Key Takeaway: A failing 12-volt battery in a BMW i3 can cause numerous strange electrical issues, such as the alarm going off randomly or other error messages. Properly replacing and registering the battery is a straightforward DIY fix for these problems.