It’s a familiar frustration for BMW owners: noticing that your key fob range is dwindling. This often signals a low battery within your key fob. BMW suggests a convenient method for wirelessly charging the key by leaving it in the car in position 1 for 24 hours. However, this isn’t always practical, especially for apartment dwellers without a personal garage. Many are looking for alternative ways to charge their key fob battery from a standard home outlet, and inductive charging is emerging as a promising DIY solution.
Exploring inductive charging sets, like those from Adafruit, opens up possibilities for home charging. A fully charged key fob offers optimal operating range, a feature noticeably diminished as the battery weakens over time, particularly with infrequent driving. While anecdotal evidence suggests some success using toothbrush chargers, a more systematic approach is needed to understand the best method.
Initial investigations into inductive charging reveal that the key fob’s receiver circuitry likely manages voltage regulation and protection. Stronger inductive coupling should lead to increased current draw from the transmitter, potentially resulting in faster charging times. Experimentation shows that placing the key fob with the BMW roundel facing the inductive charging loop maximizes current draw – approximately 75mA above the idle current. Understanding the coil positioning within the factory in-vehicle inductive charging system could offer valuable insights for optimizing DIY charging setups. Disassembling an old in-car charger might reveal these design secrets, satisfying this curiosity and potentially improving home-based charging solutions.
The BMW key fob typically utilizes a Panasonic VL-2020 battery, known for its 20mAh capacity and a standard charge current of just 1.5mA. Based on these specifications, a full charge should theoretically be achievable in well under 20 hours using a compatible inductive charging method. Further research and experimentation in this area promise convenient and effective ways to maintain a charged BMW key fob battery outside of the vehicle.
