Are you experiencing issues with your BMW 5 Series key fob, especially in cold weather? Does it sometimes fail to lock or unlock your car, or do your personalized settings reset after starting the engine? These can be common signs of a low battery in your key fob. Instead of rushing to a dealership and paying a premium, you can easily replace the battery yourself. This guide will walk you through the process of replacing your BMW 5 Series key fob battery, focusing on the correct battery type and providing step-by-step instructions.
Knowing the correct battery type is crucial for a successful DIY replacement. For most BMW 5 Series key fobs, the battery you’ll need is a VL2020 lithium-ion rechargeable battery. This 3V coin cell battery is specifically designed for key fobs and provides reliable power. You can typically find these batteries online from retailers like eBay or Amazon, ensuring you purchase a genuine VL2020 battery for optimal performance and longevity.
Before you begin, gather the necessary tools. You’ll need:
- A new VL2020 battery
- A sharp X-acto knife or similar precision cutting tool
- A non-metallic pry tool (a credit card or plastic spudger works well)
- A soldering iron and solder
Now, let’s get started with the battery replacement process:
Step 1: Purchase the Correct VL2020 Battery
Make sure you have the right replacement battery. Search online for “VL2020 battery” and ensure it matches the specifications mentioned earlier. Having the correct battery type is the first step to a successful repair.
Step 2: Carefully Open the Key Fob Casing
The BMW key fob is sealed and requires careful opening. Using your sharp X-acto knife, gently begin to cut along the seam of the key fob. Take your time and avoid applying too much pressure to prevent damage to the internal circuit board (PCB). Work your way around the entire perimeter of the fob, gradually separating the top and bottom halves of the casing.
Continue cutting along the seam until you can carefully pry the two halves apart. Be patient and methodical during this step to avoid cracking the plastic or damaging internal components.
Step 3: Desoldering the Old Battery
Once the key fob is open, you’ll see the PCB with the battery soldered in place. To remove the old battery, you’ll need to desolder it. Use your non-metallic pry tool (like a credit card) to gently apply a small amount of upward pressure to the battery. Then, using your soldering iron, heat the solder joint on one of the battery terminals (start with the corner terminal as suggested in the original guide). As the solder melts, the pry tool will help to slightly lift the terminal. Repeat this process for the other terminal until the old battery is free.
Step 4: Soldering the New VL2020 Battery
Now it’s time to install the new VL2020 battery. Place the new battery into the battery holes on the PCB, ensuring the polarity is correct (match the orientation of the old battery). Hold the PCB by the edges and gently press down on the new battery to seat it properly. Apply heat with your soldering iron to the battery terminals on the PCB. The existing solder will melt and secure the new battery in place. Start by soldering the middle terminal, followed by the corner terminal, ensuring a good connection.
Ensure both terminals are securely soldered for a reliable power supply to your key fob.
Step 5: Testing and Reassembly
Before sealing the key fob back up, it’s crucial to test if the new battery is working. Insert the PCB back into the key fob housing and test the key fob’s functions: locking, unlocking, and starting the car. Also, check if your personalized settings are now being retained. If everything works as expected, you’ve successfully replaced your BMW 5 Series key fob battery!
For reassembly, you have a couple of options. You can purchase a new key fob housing for a fresh look. Alternatively, you can simply glue the original housing back together. If you choose to glue it, use a gel-type cyanoacrylate glue sparingly to avoid it running and potentially damaging the PCB. Apply a small amount of glue to the edges of the housing and carefully press the two halves back together.
By following these steps, you can confidently replace your BMW 5 Series key fob battery and resolve common issues related to low battery power, saving time and money. Remember to always use the correct VL2020 battery type for optimal performance and longevity.
