BMW i3 Rex 12V Battery Replacement Guide | Reliable Replacement & Expert Tips
Keeping your BMW i3 Rex’s 12V rex battery in top shape ensures reliable starting and smooth electrical performance—don’t overlook this small but vital component.
Understanding the BMW i3 Rex 12V Battery System
The BMW i3 Rex relies on a 12V lead-acid battery to power essential systems like lights, infotainment, and security features. Over time, corrosion, sulfation, or wear can degrade performance, making timely replacement crucial for maintaining vehicle reliability and avoiding unexpected breakdowns.
Signs Your i3 Rex 12V Battery Needs Replacement
Watch for symptoms such as slow engine cranking, flickering dashboard lights, malfunctioning power windows, or a dead battery despite recent charging. If the battery fails intermittently, replacement is often the most effective fix—especially before full system failure occurs.
Step-by-Step BMW i3 Rex 12V Battery Replacement Process
Begin by disconnecting the vehicle’s negative terminal to prevent electrical shorts. Remove the old battery from its tray, clean corrosion from terminals using a wire brush and baking soda solution, inspect the battery case for cracks, install the new 12V rex battery securely, reconnect terminals in reverse order, and test the system to confirm proper function.
Choosing the Right Battery & Maintenance Tips
Opt for an OEM or high-quality aftermarket 12V battery with your i3 Rex’s specifications. Regularly check terminals for cleanliness, ensure secure mounting, and schedule annual inspections to extend lifespan and prevent future issues.
Proper BMW i3 Rex 12V battery replacement is key to preserving your electric vehicle’s reliability and performance. Whether you’re replacing it yourself or consulting a professional, following the right steps ensures a smooth, long-lasting fix—keep your i3 Rex running smoothly every day.
I got the 12V battery change ahead of me and wanted to put together a writeup how to get it done correctly the first time. Watched every Youtube on that topic and read all threads here with "12v" in the title. 0.
Day before - Charge new 12V battery all the way up, make sure you don't have to go. In this video, we'll guide you through the steps to remove and install the 12-volt battery on a 2014-2021 BMW i3. The vehicle featured is a 2016 BMW i3 with a Range Extender (REx) engine.
BMW i3 Body Specifications The i3 is offered in a single five-door configuration with a passenger module made from high-strength, ultra-lightweight CFRP (carbon fiber reinforced polymer) mated to a lower aluminum module holding the chassis, battery, drive system and powertrain. The rear entry features two smaller clamshell rear. The AUX18L by East Penn / Deka is an AGM, auxiliary battery typically found in hybrid, electric and start.
I'm on my second BMW i3, bought it recently (2017 120AH REX). I saw a post on here when I got my first BMW i3 (2015 90AH REX) advising to replace the 12V battery, which I did at the time. I've replaced two i3 12v batteries myself and sourced oem batteries for cost, But I found a mobile certified mechanic who will replace the battery with the East Penn Deka OEM and register the battery for $350.
The BMW i3 is a unique electric vehicle that combines sustainability with performance. However, like any car, it has its maintenance needs, and one of the most crucial components is the 12V battery. This battery is responsible for powering essential systems such as lights, infotainment, and safety features.
Over time, the 12V battery can wear []. In this video we walk through the entire battery replacement process step by step; including how to register the new battery with the cars computer using the BimmerLink app. Hybrid Mobile Repair specializes in BMW i3 REx battery replacement and reconditioning.
We will repair or replace your i3 REx battery and get you back on the road fast for a price that is about half of what the dealership charges. It's a 2017 REx with an August 2016 build date and I replaced the (original) 12V in January 2022, so it lasted just under 5 and a half years. If the car is 5 years old and you don't know that the 12V has already been replaced, I would order the replacement battery now and change it when it's convenient rather than when the car decides it wants.