Replace Mini Key Replacement Cost Uk Key Fob Batteries If your key fob is equipped with batteries that need to be replaced, it's an affordable and simple fix. Be aware that it might require reprogramming or activated. This will ensure that your car's Driver Profile is linked to the new key fob, and all of its settings including mirror position as well as seat positioning. Battery Modern key fobs provide superior functionality and convenience over a traditional car remote or flip key. However, this innovation does not come with a cost: the battery inside the key fob will eventually degrade. If you wait until it's completely gone then you could be left with no means to unlock your car. Replace your car key fob's battery immediately the power starts to diminish. You can make use of a key fob'mini cooper s replacement key led light to test its battery's voltage. If the buttons on the key fob fail to activate after pressing them and the battery dies, it is dead or dead-to-nearly dead.