My battery light stays on while driving, electrics are being erratic, then car died, what could be the problem ?

The "battery light" is the warning light telling you the battery is not being charged....NOT that you have a bad battery! You have a bad alternator! The motor quits working because when you drive you use up all the power in the battery. All the lights come on because the motor quit. It's just like when you turn the key to the on position before cranking the motor over.

Your alternator has failed.

Sounds like your alternator then.

The alternator is out! Did you BUY a new battery? Bad move!
You need an alternator replacement.

Possibly the alternator had died. That is a device that generates electricity while the engine is running. That electricity is used to drive the car's electrics and recharge the battery. If the alternator is dead then you'll be drawing all power from the battery which will eventually make it go flat. That could explain the symptoms.

Everybody overcomplicates everything when misunderstanding.

The "battery" light, in general means that the charging system is not working. The two most popular reasons for this are:

1. Alternator is not charging because of an electrical/electronic problem in the alternator/voltage regulator.

2. Alternator is not charging because the belt came off.

Continuing to drive with the battery light on stresses the battery by running it down. If this goes too long, the engine will shut off. Replacing the battery will allow the engine to start and run, but soon the replacement battery will run down and the engine will shut off. The charging system needs to be repaired.

p.s. I have no idea what "got tracking done" means!

The Alternator is not charging your battery, so your car is using all the power from the battery, and when the battery is out of power then the car dies, you will need a new alternator they cost somewhere between 50-100 dollars depending on the type of vehicle.

Alternator has pooped a biscuit. it's done.

Normal conditions:
Battery voltage at rest (engine not running, sitting over night) should be 12.6 volts.
Start the car; battery voltage should go up to 14.4 volts for a few minutes then settle down to around 13.8 volts.
Turn on all the electrics. Battery voltage should not drop below 13.6 volts.
Under these conditions your battery is good and your alternator is good.

Bad battery conditions:
Battery voltage at rest should not be below 12.00 volts. I changed the battery in my truck when it was slow to start and the resting voltage was 12.05 volts.
Start the car. Battery voltage should NOT go above 14.4 volts. If it does it's possible the fluid level may be low.
Under these conditions the battery should be changed.

Bad alternator conditions: (assuming the battery has been charged over night)
Battery voltage should be 12.6 volts at rest.
Start the car. Battery voltage may not go up to 14.4 volts but should at the very least be at 13.6 volts. Between 13.6 and 14.4 the alternator is doing something. At 13.6 the battery is not drawing much charge, so that's possible. But under a bad alternator condition the alternator is failing to put out sufficient current to charge the battery and carry all the electrics.
Turn on all the electrics. The battery voltage drops below 13.6 volts, the alternator is not keeping up with the demand. Possible causes of that may be due to a bad belt. A slipping belt can cause an alternator to appear bad. Check the belt. WITH THE ENGINE OFF - NOT RUNNING - turn the alternator by hand. If the entire engine rotates when you turn the alternator then the belt is not slipping. But if you can turn the alternator and the crank shaft does not turn then the belt is slipping. Either it's loose or worn. A glazed belt can cause slipping.

Going to AutoZone (or any other auto parts store that tests batteries and alternators) may not prove out the entire problem. Most kids don't know about slipping belts being a problem. I get a lot of thumbs down every time I mention slipping belts. Still, I've seen it many times. My own vehicle (1972 Chevy Nova), my wife's cars (1989 Toyota Celica and her 2003 Hyundai Sonata) both had slipping belts. Many friends and workmates had slipping belts causing dead batteries after driving with the headlights on (which is often the first sign of a slipping alternator belt). So belts CAN cause the battery to not be charged properly.

Recap:
Normal resting voltage 12.6 volts
Normal idling voltage 13.8 to 14.4 volts

Bad battery (with a good alternator, engine off) 12.00 volts
Bad alternator (with a good battery, engine running) fails to produce minimum 13.6 volts with all electrics running.

Slipping fan belt (engine running) all electrics off, alternator produces 13.8 volts. But when you switch on all the electrics, the voltage drops below 13.6 volts.

Assuming the serpentine belt is in place and correctly tensioned the alternator itself is suspect. You can easily test the alternator output with a cheap digital multimeter. See link.

Commonly, that's how it is when the alternator fails. If this is a Ford, first make sure the charging system fuse is not blown out. Better to need a $1 fuse instead of a $300 alternator.