Is your BMW E90 key fob acting up, especially when the temperatures drop? You might be facing the common issue of a low or dead key fob battery. If you’re noticing symptoms like reduced range, inconsistent locking/unlocking, or your BMW forgetting personalized settings, a battery replacement is likely the solution. Don’t rush to the dealership and spend a fortune. You can easily tackle this yourself with a few tools and a bit of patience. This guide will walk you through replacing your Bmw E90 Key Fob Battery, saving you time and money.
Before we begin, it’s important to note that this process involves opening your key fob and performing some basic soldering. If you’re uncomfortable with these steps, it’s always best to consult a professional. However, for the DIY enthusiast, this is a straightforward task.
What You’ll Need for Your BMW E90 Key Fob Battery Replacement
To successfully replace your BMW E90 key fob battery, gather these essential items:
- Replacement Battery: You’ll need a VL2020 lithium-ion battery. Ensure you purchase the correct type. A quick search online for “VL2020 battery” will provide numerous options. Double-check the terminal orientation (approximately 90 degrees offset) to match your original battery. You can often find these on online marketplaces like eBay or Amazon.
- Precision Screwdriver Set: While not strictly screws, having a set with small flat-head screwdrivers can be helpful for prying.
- Sharp X-Acto Knife or Similar Precision Knife: This is crucial for carefully cutting open the glued key fob casing.
- Soldering Iron and Solder: A basic soldering iron and some solder are necessary to remove the old battery and attach the new one.
- Non-Metallic Pry Tool (Credit Card or Plastic Spudger): A credit card or a plastic spudger will help you gently pry the battery without damaging the circuit board.
- Cyanoacrylate Glue (Super Glue) or New Key Fob Housing (Optional): To reassemble the key fob, you’ll need glue or a replacement housing.
Step-by-Step Guide to BMW E90 Key Fob Battery Replacement
Now, let’s get to the step-by-step process of replacing your BMW E90 key fob battery.
Step 1: Purchase the Correct Replacement Battery
Before you start taking apart your key fob, make sure you have the correct replacement battery. For the BMW E90 key fob, you need a VL2020 lithium-ion rechargeable battery. It’s vital to verify the terminal placement on the new battery matches your old one before purchasing. Online retailers specializing in batteries or automotive parts are your best bet.
Step 2: Carefully Open the Key Fob Casing
The BMW E90 key fob is notoriously sealed with glue. This is the most delicate part of the process. Take your sharp X-Acto knife and carefully begin to cut along the seam of the key fob. Important: Apply gentle pressure and make multiple shallow passes rather than trying to force it open in one go. Cutting too deep can damage the internal circuit board (PCB), rendering your key fob useless. Work slowly and methodically around the entire perimeter of the fob until you can gently pry it open.
Step 3: Desoldering the Old Battery
Once the key fob is open, you’ll see the circuit board with the battery soldered in place. To remove the old battery, you’ll need your soldering iron.
- Apply Tension: Use your non-metallic pry tool (credit card or plastic spudger) to gently apply a small amount of upward pressure to the battery. This will create a slight gap and make it easier to desolder.
- Desolder Terminals: Start with the corner terminal of the battery. Apply heat from your soldering iron to the solder joint until the solder melts. Once molten, the battery terminal should release. Repeat this process for the other terminal. The corner terminal is recommended first because the middle terminal’s lead is longer and harder to access for prying initially.
Step 4: Soldering the New Battery
With the old battery removed, it’s time to install the new VL2020 battery.
- Position the New Battery: Place the new battery into the battery holes on the PCB, ensuring the correct orientation (terminals matching).
- Solder Terminals: Hold the PCB by its edges and apply slight downward pressure on the new battery to ensure good contact with the solder pads. Apply heat to the middle terminal first, then the corner terminal. The heat will melt the existing solder, and the battery terminals will push through and settle into place. Ensure a solid solder joint for each terminal.
Step 5: Test and Reassemble Your BMW E90 Key Fob
Before fully reassembling the key fob, it’s crucial to test if the new battery is working correctly.
- Dry Fit and Test: Carefully place the PCB back into the key fob housing halves without gluing them shut.
- Test Key Fob Functions: Go to your BMW E90 and test all key fob functions: locking, unlocking, and starting the car. Also, check if your personalized settings are now being retained.
- Troubleshooting (If Necessary): If the key fob still doesn’t work, double-check your solder connections, battery orientation, and battery type. If you’re unsure, seeking professional help might be necessary.
Step 6: Closing the Key Fob
If everything is working correctly, you can now permanently close the key fob. You have two options:
- Glue the Original Housing: If you choose to reuse the original housing, carefully apply a small amount of gel-type cyanoacrylate glue (super glue) to the seam. Gel glue is recommended as it’s less likely to run and get onto the PCB. Press the two halves of the key fob firmly together and allow the glue to dry completely.
- Replace the Housing: For a more aesthetically pleasing result, you can purchase a new replacement key fob housing online. Simply transfer the PCB into the new housing and snap it shut.
Conclusion
Replacing your BMW E90 key fob battery is a cost-effective DIY solution to common key fob issues, especially in cold climates. By following these steps carefully, you can restore your key fob’s functionality and avoid expensive dealership service. Remember to take your time, be patient, and double-check each step for a successful BMW E90 key fob battery replacement. Enjoy the satisfaction of fixing it yourself!
