Is your BMW 3 Series key fob acting up, especially when the weather gets cold? You might be experiencing the common issue of a dying key fob battery. Symptoms like reduced range, inconsistent locking/unlocking, or loss of personalized car settings can point to a battery that needs replacing. Fortunately, changing the battery in your BMW 3 Series key fob is a straightforward DIY task that can save you a trip to the dealership and some money. This guide will walk you through each step to get your key fob working like new again.
What You’ll Need to Change Your BMW Key Fob Battery
Before you begin, gather these essential items to ensure a smooth battery replacement process:
- Replacement Battery: You’ll need a VL2020 lithium-ion rechargeable battery. This specific battery type is crucial for BMW 3 Series key fobs. You can find these online from reputable retailers. Ensure you note the terminal orientation of your old battery before purchasing to match the new one correctly.
- Sharp X-Acto Knife or Precision Blade: The BMW key fob is sealed and glued, so a sharp blade is necessary to carefully open the casing.
- Non-Metallic Pry Tool: A credit card or plastic pry tool will help gently lift the battery without damaging the circuit board.
- Soldering Iron and Solder: Basic soldering skills are required to remove the old battery and install the new one.
- Optional: New Key Fob Housing: If your current housing is damaged or you want a fresh look, you can purchase a replacement housing.
- Optional: Cyanoacrylate Glue (Gel Type): If you’re reusing your old housing, gel-type super glue is ideal for resealing the fob without it running into the internal components.
Step-by-Step Guide to BMW Key Fob Battery Replacement
Follow these detailed steps to replace your BMW 3 Series key fob battery successfully:
Step 1: Carefully Open the Key Fob Casing
The BMW key fob is tightly sealed. Using your sharp X-Acto knife, carefully begin to cut along the seam of the key fob casing. It’s crucial to apply gentle pressure and make multiple passes rather than trying to force it open in one go. Work slowly and methodically around the entire perimeter of the fob. Avoid cutting too deep to prevent damage to the internal circuit board (PCB). Take your time to gradually separate the top and bottom halves of the key fob.
Step 2: Desolder the Old Battery
Once the key fob is open, you’ll see the circuit board with the battery. To remove the old battery, you’ll need to desolder it. Using a non-metallic pry tool like a credit card, gently apply a small amount of pressure to lift the battery from the PCB. Focus on the corner terminal first. Apply heat with your soldering iron to the corner terminal solder joint while maintaining slight upward pressure with your pry tool. The corner terminal is easier to access initially. Once the corner terminal is free, repeat this process for the middle terminal to fully remove the old VL2020 battery.
Step 3: Solder the New Battery
Now it’s time to install the new VL2020 battery. Place the new battery into the battery holes on the PCB, ensuring correct terminal alignment (matching the orientation of the battery you removed). Hold the PCB gently by its edges and apply slight downward pressure onto the new battery to ensure it sits flush against the board. Apply heat with your soldering iron to the middle terminal pad on the PCB, allowing the solder to flow and secure the battery terminal. Repeat this soldering process for the corner terminal to firmly attach the new battery to the circuit board.
Step 4: Test and Reassemble Your Key Fob
Before permanently sealing the key fob, it’s essential to test if the new battery is working correctly. Dry fit the PCB back into the key fob housing and test all key functions – locking, unlocking, and starting your BMW 3 Series. If everything works as expected, congratulations! You’ve successfully replaced your BMW key fob battery.
For reassembly, you have two options. You can either purchase a new key fob housing for a fresh, seamless look and feel. Alternatively, if you’re happy with your existing housing, you can carefully apply a small amount of gel-type cyanoacrylate glue along the seam and press the two halves of the key fob together to reseal it. Use the glue sparingly to avoid any excess seeping into the internal components.
Conclusion
Changing your BMW 3 Series key fob battery is a manageable DIY project that can restore your key fob’s functionality and save you money. By following these steps and taking your time, you can easily replace the battery and get back to enjoying the convenience of a fully working key fob.
