Sometimes when at idle or a crawl if I push down on brake pedal my battery voltage will go down to about 10 amps and when I let off it goes back to normal.I also have the voltage flicker up and down with my turn signal .What would the brakes have to do with voltage.Battery is 3 months old.I know these cars are old and electrical has bugs and wear but the braking freaks me out a bit.

its most likely the brake light using the voltage my old '88 used to do that sometimes, and the same with the blinkers, its could also be the abs but i really dont know much about that..

No need to worry. These cars did that when they rolled off the assembly line. Just one of those quirky things about them. The brake lights are like 6 bulbs IIRC, little bit of amperage being pulled there...and lights on with brake lights is about 16 bulbs and two halogens, so if the alt can handle your lights and brake lights and the battery light doesn't come on, your alternator is fine. You'll get a bright red light if it isn't.