Changing light intensity over time via mathf.lerp

Hi guys,
sorry to bother. I really hope this is not too stupid, but I don’t manage to get it right.
So, what I want to do:
if [Event] change the intensity of a point light from 0.01 to 1.5 over x seconds under a certain condition.

My Code:

public class LightWall : MonoBehaviour {

//	public float timer = 10.0f;
	public Light lt;



	// Use this for initialization
	void Start () 
	{
		lt = GetComponent<Light>();
	}
	
	// Update is called once per frame
	void Update () 
	{
//		FIRST METHOD THAT DID NOT WORK
//		timer -= Time.deltaTime;
//		if (timer <= 0)
//			LightIntensity ();

//		ANOTHER TRY VIA PUBLIC STATIC BOOL
//		if (outer_fadein.fadeBegin == true)
			LightIntensity ();
	}

	void LightIntensity ()
	{
		lt.intensity = Mathf.Lerp (0.01f , 1.5f , Time.time/5);
		Debug.Log ("LightIntensity =" + lt.intensity + Time.time);
	}
}

The Problem:
If I simply call the function in Update, it will increase the light perfectly fine from 0.01 to 1.5. But I only want this to happen after 10 seconds, or better, after fadebegin is set to true. When I try it with one of the two conditions, the light intensity apruptly strikes in instead of beginning at 0.01.
Don’t know if it’s valuable info, but: outer_fadein.fadeBegin will be set to true after 10.00 seconds.

Thanks for the help, I really appreciate!

Cheers!

EDIT:
I think the problem is Time.time in

lt.intensity = Mathf.Lerp (0.01f , 1.5f , Time.time/5);

Since Time.time (which is in my understanding global time since app started) is not 0 when fadeBegin is set to true, intensity will not begin at 0.01f, correct?

How do I solve this? I definetly want this fade to be controlled over a time based value and not being dependant on framerates.

I think I might be a little too late to help but for anyone that still is looking at this for help like I was,
you were right about Time.time being wrong this would be how you fix it.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class LightFlicker : MonoBehaviour
{
	public float maxRange = 11;
	public float minRange = 6;
	public float flickerSpeed = 0.5f;

	private Light lightSource;

	public void Start()
	{
		lightSource = GetComponent<Light>();
	}

	public void Update()
	{
		lightSource.intensity = Mathf.Lerp(minRange, maxRange, Mathf.PingPong(Time.time, flickerSpeed));
	}
}

I used this for my campfire flicker script, for something like fire setting the maxRange to 11 and the minRange to 6 with a speed of 0.5 is pretty good.

EDITED in first Post