Hydraulic car brakes can't be "completely dead". You step on a pedal, pedal pushes piston against hydraulic fluid, this increases pressure in the hydraulic flui

Hydraulic car brakes can't be "completely dead". You step on a pedal, pedal pushes piston against hydraulic fluid, this increases pressure in the hydraulic fluid, fluid pushes a piston inside the brake caliper, piston pushes brake pads against rotor. No electricity involved.