battery light

Ok my battery light turned on and I changed my alternator and I checked my battery and I even recharged it.
I made sure the belt is tight and the light still comes on. I made sure every thing was connected and grounded right.
Is their something that I missed or did not check right?
Oh and my car never turns of on me and is been a month running with the light on.

What was the last thing you did to your car before the light came on?

I had took my chip off my ecu and installed it wrong. But the light turned on like 30min later of driving.

Ok so theirs something else going on.
When im driving, the car sometimes just stops giving power, I step on the gas and it won’t go any more but I hear the engine rev low.
Then the car just dies when it hits zero.
Please help.