Experiencing a low battery warning on your Mini Cooper’s dashboard can be more than just a minor inconvenience. For many Mini owners, especially those without the comfort access package, this warning signals a potential hurdle: the dreaded sealed key fob. Unlike key fobs with easily replaceable batteries, these sealed units are designed by BMW/Mini to discourage DIY battery changes, often leading owners to expensive dealership replacements.
But fear not! Replacing the battery in your sealed Mini key fob is absolutely achievable at home with some patience and the right guidance. This comprehensive guide will walk you through each step of opening your Mini key fob and replacing its battery, saving you a significant amount of money and extending the life of your key fob.
Before we dive in, it’s helpful to understand the different types of Mini key fobs. Some models come with a comfort package, which conveniently includes a key fob with a replaceable battery. These are straightforward to handle, as illustrated in the owner’s manual.
However, if your Mini, like many others, doesn’t have this comfort package, you’re likely dealing with a sealed key fob. This design implies no visible screws or easy access points for battery replacement. Faced with potentially high costs for a new key fob from BMW/Mini, many resourceful owners are choosing the DIY route.
This guide is for those who prefer to tackle this task themselves. We’ll show you how to carefully open your sealed Mini key fob, identify the battery, replace it, and reassemble everything. Let’s get started!
First, let’s familiarize ourselves with the standard Mini key fob. This is the type we’ll be working on in this guide.
Even with a dead battery, your Mini key fob has a backup plan. A mechanical key is hidden inside, allowing you to manually unlock and operate your vehicle. This is crucial if your battery completely dies before you get a chance to replace it.
Tools You’ll Need to Open Your Mini Key Fob
Before you begin, gather these tools:
- Sharp Knife or Precision Blade: A very sharp knife is essential for carefully cutting along the sealed edges of the key fob. The sharper, the cleaner the cut, and the easier it will be to open.
- Small Flathead Screwdriver or Pry Tool: This will be used to gently pry open the key fob casing once you’ve cut through the adhesive.
- Soldering Iron and Solder: For desoldering the old battery and soldering in the new one. If you’re not comfortable soldering, consider seeking help from someone experienced or a local electronics repair shop.
- New VL2020 Battery: This is the specific rechargeable battery type used in most sealed Mini key fobs. Ensure you order the correct type, paying attention to the orientation of the connector clips.
- Multimeter (Optional but Recommended): To check the polarity of the battery and ensure correct installation.
- Plastic Glue or Epoxy: To re-seal the key fob casing after battery replacement.
- Clamps or Rubber Bands: To hold the key fob casing together while the glue dries.
- Dremel or Small Files (Optional): For refining the edges of the key fob casing during reassembly, especially if the initial opening was not perfectly clean.
- Electro Cleaner (Optional): To clean the micro-switches inside the key fob for optimal performance.
Step-by-Step Guide to Opening and Battery Replacement
Now, let’s get to the actual process of opening your Mini key fob and replacing the battery.
Step 1: Removing the Chrome Ring (Caution Advised)
The first step is to remove the chrome ring that surrounds the key fob. Many online videos show this being done easily, but be warned: this ring is delicate and can break easily.
Using a small flathead screwdriver or pry tool, carefully try to lift the edge of the chrome ring. Work slowly and patiently around the circumference. Even with utmost care, as seen in the image, the ring can still be damaged. Proceed with caution, understanding this part might not survive the process intact.
Step 2: Carefully Separating the Key Fob Casing
This is the most crucial and delicate part. You need to cut through the glued seam that holds the two halves of the key fob together.
Secure the key fob in a way that allows for safe and controlled cutting. A vise with soft jaws or a block of wood can be helpful to stabilize the key fob. Using your sharp knife, carefully slice along the seam that runs around the entire perimeter of the key fob. Apply steady, even pressure and go slowly. Multiple passes with light pressure are better than trying to force it open in one go. The goal is to cut through the glue without damaging the plastic casing too much.
Once you have cut deep enough around the entire circumference, gently try to pry the two halves apart using your flathead screwdriver or pry tool. Work your way around the seam, gently increasing pressure until the two halves separate.
Step 3: Accessing the Circuit Board and Battery
With the casing open, the internal circuit board should be easily accessible. In most cases, it will simply lift out.
You’ll now see the battery attached to the circuit board. It’s typically soldered in place.
Step 4: Desoldering and Replacing the Battery (VL2020)
Carefully desolder the old battery from the circuit board. Take note of the battery’s orientation (+ and – terminals) before removal. A little heat from the soldering iron applied to the solder points should allow you to gently lift the battery and its clips away from the board.
The battery is a Panasonic VL2020-1HFN rechargeable battery, commonly used in Mini and BMW key fobs.
When ordering a replacement, make sure to check that the connector clips are in the same orientation as your original battery. Some VL2020 batteries come with clips at different angles (90, 120, or 180 degrees). The Mini key fob typically uses the 180-degree clip orientation.
Before soldering the new battery, take a moment to examine the circuit board. You’ll see micro-switches, which can sometimes wear out. Cleaning them with an electro cleaner at this stage can be a good preventative measure.
On the back of the circuit board, you’ll notice a coil, part of the induction charging system that charges the battery when the key fob is placed in the dash.
Solder the new VL2020 battery in place, ensuring correct polarity and secure connections. Double-check your soldering work to make sure the battery is firmly attached and in the correct orientation.
Important Note: While working with electronic components, electrostatic discharge (ESD) is a potential risk. For optimal protection, especially in sensitive environments, using an earthed workstation and wearing an anti-static wrist strap is recommended. However, for a simple battery replacement like this, taking reasonable care to ground yourself by touching a grounded metal object before handling the circuit board is often sufficient.
Step 5: Reassembling the Key Fob
With the new battery soldered in, it’s time to reassemble the key fob. Carefully align the two halves of the casing.
Before gluing, test the mechanical key mechanism to ensure it works correctly after reassembly. Make sure the key locks and unlocks smoothly.
Apply plastic glue or epoxy to the edges of the casing. Clamp or use rubber bands to hold the two halves firmly together while the glue dries completely, ideally for 24 hours.
Finally, if needed, use a Dremel or small files to refine the edges where you cut the casing to improve the fit and finish. Reattaching the chrome ring can be tricky, especially if it was damaged during removal. It might require some careful shaping and adjustment to fit properly again.
Tips for Success and Troubleshooting
- Sharp Knife is Key: Using a very sharp knife makes the opening process much cleaner and easier.
- Patience is a Virtue: Take your time during each step, especially when cutting and prying the casing. Rushing can lead to damage.
- Battery Orientation: Double-check the polarity and clip orientation of the new battery before soldering.
- Soldering Skills: If you are not comfortable soldering, seek assistance from someone with experience. Incorrect soldering can damage the circuit board.
- Test Before Gluing: Always test the key fob functionality (locking, unlocking, starting the car if possible) before permanently gluing the casing back together.
- Casing Alignment: Getting the casing perfectly aligned during reassembly can be challenging due to the nature of the initial cut. Take your time and use files or a Dremel to refine the edges for a better fit.
Conclusion: Save Money and Extend Your Key Fob Life
By following these steps, you can successfully open your sealed Mini key fob and replace its battery. This DIY approach not only saves you a considerable amount compared to dealership replacement costs but also provides a satisfying sense of accomplishment. You’ve extended the life of your key fob and avoided unnecessary expense. With a bit of care and patience, this is a manageable task for any Mini owner.
