ID see how battery affected it, unless you somehow damaged an ABS cable. Try unplugging sensor from LF, If you have it (I go far. making an assumption,) If that don't fix it, do as Geo Metro sez; crack the bleeder, isolate problem.
You Don't need to replace rotor or pads or caliper, necessarily. Until it is Looked At. No one here has a crystal ball. Might have caught all in time.