flashLight regeneration

Hi i need some help i would like to make the Flash light regeneration when the flashlight is off it should regeneration the light Here is a script i found for the flashlight to turn off it has audio source and BatteryLife!!! the battery life is only for flashlight how much battery it has till it dosent turn off

so basically could any one know how to add Regeneration in this script? when the flashlight is off the battery is charing

Sorry for bad eng :P

 #pragma strict
 
 var flashlightLightSource : Light;
 var lightOn : boolean = true;
 var lightDrain : float = 0.1;
 var batteryLife : float = 0.0;
 var maxBatteryLife : float = 2.0;
 
 var barDisplay : float = 0;
 var pos : Vector2 = new Vector2(20,40);
 var size : Vector2 = new Vector2(60,20);
 var progressBarEmpty : Texture2D;
 var progressBarFull : Texture2D;
 
 var soundTurnOn : AudioClip;
 var soundTurnOff : AudioClip;
 
 
 function Start()
 {
     batteryLife = maxBatteryLife;
     flashlightLightSource = GetComponent(Light);
 }
 
 function Update()
 {
 
 //BATTERY LIFE BRIGHTNESS//////////
     if(lightOn && batteryLife >= 0)
     {
         batteryLife -= Time.deltaTime * lightDrain;
     }
         if(lightOn && batteryLife <= 0.4)
     {
         flashlightLightSource.light.intensity = 0.4;
     }
         if(lightOn && batteryLife <= 0.3)
     {
         flashlightLightSource.light.intensity = 0.8;
     }
     if(lightOn && batteryLife <= 0.2)
     {
         flashlightLightSource.light.intensity = 0.4;
     }
         if(lightOn && batteryLife <= 0.1)
     {
         flashlightLightSource.light.intensity = 0.2;
     }
             if(lightOn && batteryLife <= 0)
     {
         flashlightLightSource.light.intensity = 0;
     }
     
 
     
     barDisplay = batteryLife;
     
     if(batteryLife <= 0)
     {
         batteryLife = 0;
         lightOn = false;
     }
     
     if(Input.GetKeyUp(KeyCode.F))
     {
         toggleFlashlight();
         toggleFlashlightSFX();
         
         if(lightOn)
         {
             lightOn = false;
         }
         else if (!lightOn && batteryLife >= 0)
         {
             lightOn = true;
         }
     }
 }
     
     /////// PIC  ///////////
 function OnGUI()
 {
  
     // draw the background:
     GUI.BeginGroup (new Rect (pos.x, pos.y, size.x, size.y));
         GUI.Box (Rect (0,0, size.x, size.y),progressBarEmpty);
  
         // draw the filled-in part:
         GUI.BeginGroup (new Rect (0, 0, size.x * barDisplay, size.y));
             GUI.Box (Rect (0,0, size.x, size.y),progressBarFull);
         GUI.EndGroup ();
  
     GUI.EndGroup ();
  
 } 
      
 function toggleFlashlight()
 {
     if(lightOn)
     {
         flashlightLightSource.enabled = false;
     }
     else
     {
         flashlightLightSource.enabled = true;
     }
 }
 function toggleFlashlightSFX()
 {
     if(flashlightLightSource.enabled)
     {
         audio.clip = soundTurnOn;
     }
     else
     {
         audio.clip = soundTurnOff;
     }
     audio.Play();
     
 }
 
     @script RequireComponent(AudioSource)