Rudy - yes, they work inside the windshield.  Obviously must be connected to a 'constant on' connection to the battery (some cigarette lighter outlets are only powered with the ignition on, which draws more than the charger puts out). Better is to disconnect the battery from the car and wire directly.  If it's a modern car with computer-driven controls, there might be a 're-education' process once re-energized.  Or, do not disconnect if the risk of problems is too great. Good luck.  Jim