BMW suggests a convenient way to wirelessly charge your key fob by leaving it in position 1 inside the car for 24 hours. However, this isn’t always practical, especially for apartment dwellers without a garage. If you’re looking for alternative ways to charge your BMW key fob at home, you’re not alone. Many owners experience a reduced operating range over time, signaling a need to recharge the key. Let’s explore how you might charge your key fob using readily available home outlets and inductive charging methods.
One approach involves experimenting with inductive charging, similar to how your BMW might charge the key fob wirelessly in the car. An Adafruit Induction Charging Set can be a useful tool for this exploration. By placing the key fob on the inductive charging loop with the BMW roundel facing down, you can observe an increase in current draw, indicating charging is taking place. In this setup, a current increase of approximately 75mA over the idle current was noted, suggesting effective inductive coupling when correctly positioned. Understanding the internal coil positioning within the car’s inductive charging system could offer further insights and potentially optimize home charging methods. It would be interesting to examine a disassembled in-car key fob charger to compare coil placements.
The BMW key fob typically utilizes a Panasonic VL-2020 battery, a rechargeable coin cell known for its 20mAh capacity and a standard charge current of just 1.5mA. This low charge current means that even with a basic inductive charging setup, achieving a full charge should be feasible within a reasonable timeframe, well under 20 hours. Some BMW owners have reported success using certain toothbrush chargers, hinting at the potential for repurposing existing inductive charging devices for key fobs. Further investigation into different inductive charging solutions and coil alignments could reveal more efficient and convenient methods for keeping your BMW key fob battery optimally charged and ensuring a reliable operating range.
