Brake warning Alarm ?

[trevor simpson]

Good afternoon chaps.
This morning when I started my 1.9 tdi 130 sport .when I turned the ignion key the red brake warning light sign came on and sounded the alarm twice ,them cancelled .Aparrently this has happened before my wife tells me , has anyone got any ideas ?
Thanks in anticipation Trevor Simpson

[kite]

its a low voltage spike when cranking.....
First sign of a dying battery...