Is your Mini Cooper displaying a “low key fob battery” warning? You’re not alone. Many Mini owners encounter this message, and if you have a model without the comfort access package, you might find yourself facing a sealed key fob. BMW and Mini often suggest professional replacement, which can be costly. However, changing the battery yourself is a viable and cost-effective option. This guide will walk you through the process of how to change your Mini key fob battery, step-by-step, empowering you to handle this common maintenance task at home.
Alt text: Mini Cooper dashboard displaying a low key fob battery warning light, indicating the need for a battery replacement.
What You’ll Need
Before you begin, gather the necessary tools. Having everything prepared will make the process smoother and more efficient. You will need:
- A small, sharp knife or precision blade (like an X-Acto knife)
- A small flat-head screwdriver or plastic pry tool
- Soldering iron and solder
- Desoldering wick or pump (optional, but helpful)
- Electro cleaner spray (optional, for micro-switches)
- Plastic glue or epoxy
- Clamps or rubber bands
- A replacement battery – Panasonic VL2020-1HFN rechargeable battery (ensure the clips are oriented correctly)
- Multimeter (for checking polarity – recommended)
- Protective eyewear
Step 1: Getting Started – Accessing the Key Fob
The first step in how to change your Mini key fob battery is to access the internal components. Begin by locating the chrome ring that surrounds the key fob. This ring needs to be carefully removed. While some videos may show this being done easily, be aware that it can be fragile.
Using a small flat-head screwdriver or a plastic pry tool, gently work around the edge of the chrome ring. Apply steady, even pressure to avoid cracking the plastic or the ring itself. Patience is key here. Slowly and carefully pry the ring upwards until it detaches from the main body of the key fob.
Alt text: Close-up of a Mini Cooper key fob with a broken chrome ring after attempting removal, highlighting the delicate nature of this part during disassembly.
Step 2: Opening the Sealed Key Fob
With the chrome ring removed, you’ll now need to open the sealed plastic casing. This is arguably the trickiest part of learning how to change your Mini key fob battery because these fobs are designed to be sealed.
Take your sharp knife or precision blade and carefully insert it into the seam that runs along the side of the key fob. Apply gentle but firm pressure to cut through the adhesive. Work your way around the entire circumference of the key fob, gradually deepening the cut. It’s crucial to maintain a firm grip and controlled movements to prevent injury. Using a vice with wood and rags to secure the fob can provide a safer working environment.
Alt text: Image showing a Mini key fob securely held in a vice with wood and rags, demonstrating a safe method for cutting open the sealed plastic casing to access internal components.
Once you’ve cut deep enough around the entire seam, gently try to separate the two halves of the key fob. You may need to run the knife along the seam again in stubborn areas. With care, the two halves should split apart, revealing the internal circuit board.
Alt text: Two halves of an opened Mini Cooper key fob are separated, displaying the internal circuit board and components after carefully cutting along the sealed seam.
Step 3: Accessing the Circuit Board and Battery
After opening the key fob, the circuit board should be easily accessible. In most cases, it will simply lift out of the casing. Carefully remove the circuit board to expose the battery.
Alt text: Mini Cooper key fob circuit board lifted out from the casing, showcasing the accessibility of internal components after opening the sealed fob.
Step 4: Desoldering the Old Battery
The old battery is soldered onto the circuit board. To remove it, you’ll need a soldering iron. Heat the solder joints connecting the battery terminals to the board. If you have desoldering wick or a pump, use it to remove the melted solder. Gently wiggle the battery as you heat the solder points until it comes free from the circuit board.
Alt text: Close-up of a soldering iron being used to desolder the old battery from the circuit board of a Mini Cooper key fob, a crucial step in the battery replacement process.
Step 5: Identifying and Ordering the Replacement Battery
Once the old battery is removed, you can identify the correct replacement. The battery in this Mini key fob is a Panasonic VL2020-1HFN rechargeable BMW-Mini battery. Take note of this part number when searching for a replacement.
When ordering a new battery online, pay close attention to the orientation and style of the connector clips. As noted in the original article, batteries of the same type can come with different clip angles (90, 120, or 180 degrees). Ensure you order a battery with clips that match the original battery in your key fob, particularly the 180-degree orientation of the + and – clips.
Alt text: Panasonic VL2020-1HFN rechargeable battery removed from a Mini Cooper key fob, clearly showing the battery type and connector clips for identification when ordering a replacement.
Step 6: Soldering the New Battery
With your new battery in hand, it’s time to solder it onto the circuit board. Before soldering, use a multimeter to double-check the polarity (+ and -) of both the old and new batteries to avoid any mistakes.
Position the new battery correctly on the circuit board, ensuring the terminals align with the solder pads. Heat the solder pads and apply solder to securely attach the new battery. Be careful not to use excessive solder and ensure a clean connection. Double-check that you’ve soldered the battery on the correct side of the circuit board, as mistakenly soldering it on the wrong side will require rework.
Alt text: Image showing the new replacement battery correctly soldered onto the circuit board of a Mini Cooper key fob, positioned at the proper height and orientation for optimal function.
Step 7: Reassembling the Key Fob
After successfully soldering the new battery, it’s time to reassemble the key fob. Carefully place the circuit board back into one half of the plastic casing. Before gluing the two halves together, test the mechanical key mechanism to ensure it’s functioning correctly. Make sure the key locks and unlocks smoothly.
Once you’re satisfied with the fit and key operation, apply plastic glue or epoxy to the edges of one half of the casing. Carefully align and press the two halves together. Use clamps or rubber bands to hold the key fob firmly together while the glue dries and hardens, ideally for 24 hours.
Alt text: Mini Cooper key fob halves being clamped together after gluing, allowing the adhesive to dry and securely reassemble the fob after battery replacement.
Refitting the chrome ring can be challenging, especially if it was damaged during removal. You may need to use a Dremel or hand files to carefully reshape the plastic edges of the key fob to ensure a snug fit for the chrome ring. Take your time and gently work the ring back into place.
Alt text: Reassembled Mini Cooper key fob with the chrome ring carefully refitted, showcasing the completed DIY battery replacement and restored fob appearance.
Step 8: Final Testing
Once the glue is fully cured and the key fob is completely reassembled, test its functionality. Try locking and unlocking your Mini Cooper remotely. Insert the key fob into the dashboard slot to check if the charging function is working and if the “low key fob battery” warning has disappeared.
Alt text: Completed and functional Mini Cooper key fob after successful DIY battery replacement, demonstrating the resolution of the low battery issue.
Congratulations! You’ve successfully completed the process of how to change your Mini key fob battery. By following these steps, you’ve saved yourself the cost of professional replacement and gained the satisfaction of DIY car maintenance. Enjoy the renewed life of your Mini key fob!
