DIY Mini Cooper Key Fob Battery Replacement: A Step-by-Step Guide

Is your Mini Cooper key fob displaying a low battery warning? Don’t rush to the dealership just yet. While BMW and Mini might prefer you replace the entire key fob, replacing the Mini Cooper Key Fob Battery yourself is a surprisingly straightforward DIY task. This guide will walk you through each step, saving you money and empowering you to handle this common car maintenance job.

The dreaded low battery warning on your Mini Cooper’s dashboard can be unsettling, especially when it concerns your key fob. Many Mini Cooper owners are unaware that the standard key fobs, particularly those without the comfort access package, are sealed units. This often leads to the misconception that battery replacement is impossible or requires professional (and costly) intervention. However, with a bit of patience and the right tools, you can easily replace your mini cooper key fob battery at home.

This guide is inspired by a DIY enthusiast’s successful attempt to replace their mini cooper key fob battery, proving that you don’t need to be an expert to tackle this task. We’ll break down the process into manageable steps, ensuring you can confidently restore your key fob’s power.

Identifying Your Mini Cooper Key Fob Type

Before you begin, it’s helpful to understand the type of key fob you have. Mini Cooper key fobs generally come in two main types:

Comfort Access Key Fobs: These fobs are designed with convenience in mind and usually have a removable battery compartment. Replacing the battery in these is typically very simple, often requiring just a small screwdriver to open the battery compartment.
Standard (Sealed) Key Fobs: If your Mini Cooper doesn’t have the comfort access package, you likely have a sealed key fob. These fobs lack an obvious battery compartment and are designed to be charged inductively in the car. While seemingly non-replaceable, the battery can be changed with a bit of careful disassembly, as we will detail in this guide.

If your key fob looks like the one pictured below, you probably have a sealed unit, and this guide is for you!

Tools You’ll Need for Mini Cooper Key Fob Battery Replacement

To successfully replace your mini cooper key fob battery, gather these tools:

Small, Sharp Knife or Precision Blade: Essential for carefully separating the glued halves of the key fob. A sharp craft knife or even a thin, sturdy kitchen knife will work.
Small Flat-Head Screwdriver or Pry Tool: Useful for gently prying apart the key fob halves once you’ve cut through the adhesive.
Soldering Iron and Solder: Required to remove the old battery and install the new one. If you’re not comfortable soldering, consider asking a friend or local electronics repair shop for assistance.
Desoldering Pump or Wick (Optional but Recommended): Makes removing the old solder much cleaner and easier.
Replacement Battery: Crucially, you’ll need the correct replacement battery. The original battery is often a Panasonic VL2020-1HFN rechargeable battery. We’ll discuss how to confirm this and find a replacement shortly.
Multimeter (Optional but Recommended): Helpful for verifying the polarity of the new battery and ensuring proper installation.
Plastic Glue or Epoxy: To re-seal the key fob halves after battery replacement.
Clamps or Rubber Bands: To hold the key fob halves together while the glue dries.
Dremel or Small Files (Optional): May be needed to refine the chrome ring after disassembly for re-fitting.
Electro Cleaner (Optional): For cleaning the micro-switches inside the key fob.
Safety Glasses: Protect your eyes during disassembly and soldering.
Work Gloves (Optional): To protect your hands.

Step-by-Step Mini Cooper Key Fob Battery Replacement Guide

Now, let’s get to the heart of the matter: replacing your mini cooper key fob battery. Follow these steps carefully:

Step 1: Prying off the Chrome Ring (Caution!)

The first step is to remove the chrome ring surrounding the key fob. This ring is often clipped or lightly glued in place.

Carefully insert a thin, flat tool (like a small flat-head screwdriver or plastic pry tool) between the chrome ring and the plastic body of the key fob.
Gently pry upwards to lift the ring. Work your way around the ring, applying gentle pressure.
Be extremely careful as this ring can be fragile. As the original author discovered, even with caution, this ring can break. Take your time and avoid excessive force.

Step 2: Carefully Opening the Key Fob

This is the trickiest part, as the key fob is glued shut.

Using your sharp knife or precision blade, carefully insert the tip into the seam running along the side of the key fob.
Begin to cut along the seam, working your way around the entire circumference of the key fob. Apply steady, even pressure. Multiple passes with a sharp blade are better than trying to force it open in one go.
Take your time and be patient. The glue can be quite strong.
Use a vise or clamps (with protective rags) to securely hold the key fob while cutting, ensuring your safety and providing stability.

Step 3: Accessing the Circuit Board and Battery

Once you’ve cut through the adhesive, you should be able to separate the two halves of the key fob.

Gently pry apart the two halves using your fingers or a small pry tool. They should separate relatively easily now that the glue is cut.
The circuit board should now be visible. In most cases, it will lift out easily.
Locate the battery on the circuit board. It’s usually a small, button-shaped rechargeable battery.

Step 4: Desoldering the Old Battery

The battery is soldered onto the circuit board with small metal clips.

Heat up your soldering iron.
Carefully apply the soldering iron to the solder joints connecting the battery clips to the circuit board.
Once the solder melts, use a desoldering pump or wick to remove the solder from the joints. This will free the battery clips.
Gently remove the old battery from the circuit board.

Step 5: Identifying and Ordering the Correct Replacement Battery

It’s crucial to get the correct replacement battery for your mini cooper key fob battery.

Note the markings on the old battery. As mentioned, the original battery is often a Panasonic VL2020-1HFN.
Search online for “Panasonic VL2020-1HFN battery” or “Mini Cooper key fob battery replacement.”
Pay close attention to the battery clips. As the original author noted, batteries with the same number can have different clip configurations (angles). Ensure the replacement battery’s clips match the orientation of the clips on your old battery (typically 180 degrees apart for the +/- terminals).
Order your replacement battery online from a reputable electronics supplier.

Step 6: Soldering the New Battery

Now, install the new mini cooper key fob battery.

Position the new battery onto the circuit board, ensuring the polarity (+ and -) is correct. Double-check with your multimeter if you are unsure.
Solder the battery clips to the circuit board at the same points where the old battery was connected. Ensure a good, solid solder joint.
Double-check your soldering and ensure the battery is securely attached and in the correct orientation.

Step 7: Reassembling the Key Fob

With the new battery soldered in, it’s time to reassemble the key fob.

Carefully place the circuit board back into one half of the key fob casing.
Apply a small amount of plastic glue or epoxy to the edges of one half of the key fob casing.
Carefully align and press the two halves of the key fob together.
Use clamps or rubber bands to hold the key fob halves firmly together while the glue dries completely (usually 24 hours is recommended for most plastic glues).

Step 8: Refitting the Chrome Ring and Testing Your Key Fob

The final steps are to refit the chrome ring and test your key fob.

Once the glue is fully dried, remove the clamps or rubber bands.
Carefully refit the chrome ring. This may require some gentle manipulation and possibly slight filing or sanding with a Dremel or small files if the plastic casing is slightly deformed from opening.
Test your key fob. Try locking and unlocking your Mini Cooper and starting the engine to ensure the new battery is working correctly.

Tips for Success and Troubleshooting

Work in a well-lit and clean workspace.
Take photos at each step as a reference during reassembly.
If you are not comfortable with soldering, seek help from someone who is experienced or a local electronics repair shop.
Double-check the battery polarity before soldering the new battery.
Be patient and gentle during disassembly and reassembly to avoid damaging the key fob components.
If the chrome ring is damaged during removal, you may need to source a replacement or carefully reshape it with files.
If your key fob still doesn’t work after battery replacement, double-check your soldering connections and battery polarity. It’s also possible the micro-switches inside the fob are worn out, although this is less common for battery issues.

Conclusion

Replacing your mini cooper key fob battery yourself is a rewarding DIY project that can save you a significant amount of money compared to dealership replacement. By following these steps carefully, you can restore your key fob’s functionality and avoid the inconvenience of a dead battery. While it requires some care and precision, especially with soldering, it’s a testament to DIY ingenuity and a practical solution for Mini Cooper owners facing a low key fob battery warning. Remember to always double-check battery compatibility and polarity for a successful mini cooper key fob battery replacement.