Is your Mini Cooper flashing a low key battery warning? You’re not alone. Many Mini owners encounter this message, often leading them to believe a costly dealership visit is the only solution. If your Mini Cooper, like many, doesn’t have the comfort access package, your key fob is likely sealed, seemingly preventing a simple battery replacement. BMW/Mini often suggests replacing the entire key fob, which can be an expensive proposition. However, don’t worry, you can tackle this yourself! This guide will walk you through replacing the battery in your sealed Mini Cooper key fob, saving you money and empowering you with a bit of DIY car maintenance.
You might be wondering about the origins of the term “key fob.” Interestingly, it’s believed to come from “watch fobs,” decorative ornaments attached to pocket watch chains as far back as 1888. The term evolved, perhaps from Middle English or German words relating to pockets or sneak-proofing, to describe the convenient remote key we use today.
While some Mini Cooper key fobs with the comfort package have easily replaceable batteries, many are sealed units. The good news is, “sealed” doesn’t mean impossible to open. With a bit of patience and the right tools, you can access and replace the battery. Let’s dive into how to do it.
First, you’ll likely notice a warning light on your Mini Cooper’s dashboard indicating a low key fob battery.
This warning is your signal that the rechargeable battery inside your key fob is nearing the end of its life. These key fobs cleverly use inductive charging when placed in the designated slot on your dashboard, eliminating the need for external charging ports.
Even with a depleted battery, your Mini Cooper key fob still has a trick up its sleeve. A hidden mechanical key is tucked inside, allowing you to manually unlock and operate your vehicle if the battery completely dies.
However, for the convenience of remote locking and unlocking, replacing the battery is the ideal solution. Here’s how to do it step-by-step:
Step-by-Step Mini Cooper Key Fob Battery Replacement
Before you begin, gather the necessary tools:
- A very sharp knife (like a craft knife or utility knife)
- Small flat-head screwdriver or plastic pry tool
- Soldering iron and solder
- Replacement battery (Panasonic VL2020-1HFN rechargeable battery)
- Electro cleaner spray (optional, for micro-switches)
- Plastic glue
- Clamps (optional, for gluing)
- Dremel or small files (optional, for refining the key fob casing after opening)
Step 1: Removing the Chrome Ring
The first step is to carefully remove the chrome ring surrounding the key fob. While videos might make this look easy, it’s a delicate part.
Using a small flat-head screwdriver or plastic pry tool, gently work your way around the ring, prying it upwards. Be extremely cautious as this ring can break easily. Slow and steady pressure is key.
Step 2: Opening the Key Fob Casing
This is the trickiest part. The key fob casing is glued together and needs to be carefully cut open. A sharp knife is essential for this step.
Secure the key fob firmly but gently. Using a vice with soft jaws or wrapping the fob in rags and clamping it to a workbench can help. Carefully score along the seam of the key fob casing with your sharp knife. Multiple passes with light pressure are better than trying to force it open in one go. Work your way around the entire circumference of the fob.
Once you’ve cut deep enough, you should be able to gently pry the two halves of the key fob casing apart.
Step 3: Accessing the Circuit Board and Battery
With the casing open, the internal circuit board should be easily accessible.
Carefully remove the circuit board from the casing. You’ll see the battery soldered onto the board.
Step 4: Desoldering the Old Battery
Now it’s time to remove the old battery. Using a soldering iron, carefully desolder the battery terminals from the circuit board. Take note of the battery’s orientation (+ and -) before removing it.
The battery is a Panasonic VL2020-1HFN rechargeable battery, specifically designed for BMW/Mini key fobs.
Step 5: Inspecting the Circuit Board
Take a moment to examine the circuit board. You’ll notice micro-switches that correspond to the buttons on your key fob. These can sometimes wear out and be replaced individually. Using electro cleaner spray on these switches can help improve their responsiveness.
On the back of the board, you’ll see the induction coil used for wireless charging.
Important Note: When working with electronic components, electrostatic discharge (ESD) is a concern. While specialized ESD workstations are ideal, for a simple battery replacement, being mindful and avoiding static build-up is usually sufficient for robust key fobs like these.
Step 6: Soldering the New Battery
When ordering a replacement VL2020-1HFN battery, pay close attention to the orientation and type of clips attached. Some batteries come with clips at different angles (90, 120, or 180 degrees). Ensure you order one with the correct clip configuration to match your original battery.
Solder the new battery onto the circuit board, ensuring correct polarity (+ and -). Double-check the orientation before soldering!
Common Mistake: Avoid soldering the battery on the wrong side of the circuit board!
If you make this mistake, carefully desolder and resolder it on the correct side. Also, ensure the battery sits at the correct height above the board for proper fitment in the casing.
Step 7: Reassembling the Key Fob
Carefully place the circuit board back into the key fob casing halves.
Check the mechanical key locking mechanism to ensure it functions correctly. Test fit the two halves of the casing to make sure they align properly.
Apply plastic glue to the seam of the casing and carefully press the two halves together. Use clamps or weights to hold the casing firmly together while the glue dries for about 24 hours.
Step 8: Refitting the Chrome Ring
Refitting the chrome ring can be fiddly, especially if it was damaged during removal.
Using a Dremel or small files, carefully refine the edges of the key fob casing if needed to ensure the chrome ring fits snugly. This step might require patience to get a good fit due to the slight imperfections from cutting the casing open.
Step 9: Testing and Enjoy!
Once everything is reassembled, test your Mini Cooper key fob. It should now be working perfectly, and the low battery warning should be gone! You’ve successfully replaced your Mini Cooper key fob battery and saved yourself a potentially expensive trip to the dealership.
Replacing your Mini Cooper key fob battery is a rewarding DIY task that can save you money and give you a sense of accomplishment. While it requires careful steps and some basic soldering skills, it’s definitely achievable for the average DIY enthusiast. Enjoy the renewed life of your key fob!
