I understand. Context was related to the vehicle. Even if the car was dead BLE module and the locking system could still function. Doesn’t take much. Would work with phone or FOB assuming the FOB was BLE as well. Even just phone is better than locked out.The 12V is in reference to the car battery, not the fob battery. With no 12V power, electronic door locks do not function.
Fob batteries are usually 3V CR2032.