Is your Mini Cooper flashing a low key fob battery warning? Don’t rush to the dealership just yet. If you’re a bit handy, you can tackle a Mini Key Fob Battery replacement yourself and save a significant amount of money. While BMW/Mini might prefer you replace the entire key fob, the truth is, it’s often just a simple battery swap that’s needed. This guide will walk you through the process of replacing the battery in a sealed Mini key fob, even if you don’t have the comfort access package with the easily replaceable battery.
Just like the author of the original post, a low battery warning on your Mini’s dashboard, similar to the one pictured above, signals that your key fob battery is nearing its end. Many modern Mini key fobs, especially those without the comfort package, are designed to be sealed units. This means the battery is intended to be charged inductively when you insert the key fob into the designated slot on the dashboard. However, like all rechargeable batteries, these will eventually degrade and require replacement.
For those with the comfort package, replacing the mini key fob battery is straightforward, as these fobs are designed with user-replaceable batteries.
However, if your Mini, like many, doesn’t have this comfort package, you might be told that the battery isn’t replaceable, necessitating a costly new key fob from BMW/Mini. But fear not! With some careful work and a bit of DIY spirit, you can perform a mini key fob battery replacement yourself. This guide will show you how to open your sealed Mini key fob and replace the battery, just like the original author successfully did.
Understanding Your Mini Key Fob and Battery
Before we dive into the replacement process, let’s understand the key fob and its battery a bit better. Your Mini key fob, even the sealed type, is a sophisticated piece of technology. It’s more than just a key; it’s a remote control for your car, enabling features like remote locking/unlocking, and in some cases, push-button start.
Even with a depleted battery, most Mini key fobs have a mechanical key hidden inside. This key, as shown in the image below, can be removed and used to manually unlock and start your car in emergencies when the battery is completely dead.
The battery inside these sealed fobs is typically a rechargeable coin cell battery. In the case of the Mini key fob in the original article, it’s a Panasonic VL2020-1HFN. These batteries are designed to be recharged through inductive charging while the key is in the dashboard slot, but they have a limited lifespan.
Tools and Materials You’ll Need
To successfully perform a mini key fob battery replacement, you’ll need to gather the following tools and materials:
- Small, sharp knife or precision blade: For carefully separating the glued key fob casing. A utility knife or even a very sharp pocket knife will work.
- Small flat-head screwdriver or plastic pry tool: To gently pry open the key fob halves once you’ve cut through the glue. Plastic tools are less likely to scratch the casing.
- Soldering iron and solder: For desoldering the old battery and soldering in the new one. If you are not comfortable soldering, consider seeking help from someone who is experienced.
- Desoldering pump or braid (optional but helpful): To remove excess solder when removing the old battery.
- Replacement battery: Identify the correct battery for your key fob. In this case, it’s the Panasonic VL2020-1HFN rechargeable battery. Ensure you order one with the correct terminal configuration (clip angles).
- Multimeter (optional but recommended): To check the polarity of the battery and ensure correct orientation before soldering.
- Electro cleaner spray (optional): To clean the micro-switches inside the key fob.
- Plastic glue or epoxy: To re-seal the key fob casing.
- Clamps or rubber bands: To hold the key fob halves together while the glue dries.
- Dremel or small files (optional): For refining the edges of the key fob casing after reassembly, if needed.
- Safety glasses: To protect your eyes during disassembly and soldering.
- Anti-static wrist strap (optional but recommended for electronics work): To prevent electrostatic discharge damage to the circuit board.
Step-by-Step Mini Key Fob Battery Replacement Guide
Now, let’s get to the actual battery replacement process. Follow these steps carefully:
Step 1: Removing the Chrome Ring (Carefully!)
The first step is to remove the chrome ring that surrounds the key fob. As the original author discovered, this ring can be fragile.
Use a small, flat plastic tool or your sharp knife to gently pry under the edge of the chrome ring. Work your way around the ring slowly and patiently. Even with care, there’s a risk of breaking it, so proceed cautiously.
Step 2: Separating the Key Fob Casing
This is the trickiest part as the key fob is glued together. You’ll need your sharp knife.
Secure the key fob in a way that allows you to safely cut along the seam. The original author used a vice and wood blocks. Be extremely careful not to cut yourself. Carefully run the knife along the entire seam of the key fob, cutting through the glue. You may need to go around multiple times, applying gentle pressure.
Step 3: Opening the Key Fob Halves
Once you’ve cut through the glue around the entire circumference, you should be able to gently pry the two halves of the key fob apart.
Use your flat-head screwdriver or plastic pry tool to assist in separating them if needed. Be gentle and avoid forcing them apart, ensuring you’ve cut through all the glue.
Step 4: Accessing the Circuit Board
With the casing open, the internal circuit board should be easily accessible.
In most cases, it will simply lift out. Handle the circuit board by its edges to avoid touching the electronic components directly.
Step 5: Desoldering the Old Battery
Now you’ll see the battery soldered onto the circuit board.
Carefully use your soldering iron to heat the solder joints of the battery terminals on the circuit board. Once the solder is molten, use a desoldering pump or braid to remove the solder. Gently remove the old battery. Note the orientation of the battery (+ and – terminals) before removing it – this is crucial for installing the new one correctly.
Step 6: Identifying the Battery Type
Take a close look at the old battery to identify the exact type. As mentioned, the original author’s battery was a Panasonic VL2020-1HFN.
Make sure you order the exact replacement, paying attention to the terminal configuration (angle and size of the clips).
Step 7: Soldering the New Battery
Place the new battery in the correct orientation onto the circuit board, matching the polarity (+ and -) of the old battery.
Solder the battery terminals securely to the circuit board. Ensure good solder joints for a reliable connection. Double-check that you’ve soldered it on the correct side of the board, as the original author initially made a mistake!
Step 8: Reassembling the Key Fob
Carefully place the circuit board back into one half of the key fob casing. Ensure it sits correctly.
Test the mechanical key mechanism to ensure it’s working smoothly before closing the casing completely. Apply plastic glue or epoxy to the edges of the casing halves and carefully press them together. Use clamps or rubber bands to hold the halves firmly together while the glue dries completely (usually 24 hours).
Step 9: Refitting the Chrome Ring
Once the glue is dry, you can attempt to refit the chrome ring. This can be fiddly, especially if it was damaged during removal.
If necessary, use a Dremel or small files to carefully refine the edges of the plastic casing to ensure a better fit for the ring. Take your time and be patient.
Step 10: Testing the Key Fob
After reassembly, test your key fob to ensure it’s working correctly. Check if the remote locking/unlocking and other functions are operational. The low battery warning on your dashboard should now be gone after driving and allowing the key fob to charge in its slot.
Conclusion: DIY Key Fob Battery Replacement Success
Congratulations! You’ve successfully completed a mini key fob battery replacement and saved yourself the cost of a new key fob. While it requires some care and a bit of technical know-how, replacing the battery in your sealed Mini key fob is a rewarding DIY task. By following these steps, you can keep your Mini key fob functioning perfectly and avoid unnecessary expenses. Remember to always double-check battery compatibility and polarity, and if you’re unsure about any step, especially soldering, seek assistance from someone with electronics experience. Enjoy the satisfaction of a job well done and a key fob that’s ready for the road!
