Today our suburban dies while sitting at a light,

I think you are right. the battery is dead. make sure the battery cables / terminals are clean and tight. Charge or replace the battery. If the battery is over three years old you should probably replace it. Once you get it started again make sure your alternator is working. this is the part that charges the battery while the car is running. Usually if it isnt working you will get a battery light on in the dash. or if you have a volt meter your battery voltage should be at about 14.30 Volts while the car is running. also make sure your belt is in good shape check for cracks and shinny surface.