The Swiss-born weather expert faces up to 15 years in prison if he is found guilty of charges he denies.
"Mr. Kachelmann requested recusal because there are concerns that the two judges in question will not face him with the necessary impartiality," said defence attorney Reinhard Birkenstock.
The case will now resume on September 13 after the suitability of the judges is determined.
Some 25 witnesses have been called to testify before the court in the southwestern state of Baden-Württemberg, among them “various female witnesses from the circle around the accused” and five experts, according to prosecutors.
Kachelmann was arrested at the Frankfurt airport on March 20, 2010 and held on remand for four months until late July. A Mannheim court had said they had insufficient evidence to continue holding him.
The alleged victim, Kachelmann's girlfriend, was the sole prosecution witness and the case was therefore “her word against his,” the court said.
It could not be ruled out that she had made false accusations, nor that she herself caused the injuries she claimed to have suffered during the rape, the court said.
A verdict in the trial is expected at the end of October.