The Swiss-born 51-year-old is suspected of raping his long-time girlfriend at knifepoint in their Schwetzing apartment in February when she tried to end their relationship, public prosecutor Andreas Grossmann said.
Kachelmann allegedly threatened to kill the woman, who sustained injuries to her throat where he pressed the knife.
The weather man and founder of Meteomedia weather service has been held since March 20 when he was arrested at the Frankfurt airport upon returning from work at the Vancouver Olympics.
He maintains his innocence.
Meanwhile prosecutors in the state of Baden-Württemberg have reportedly based their case on the alleged victim's testimony, forensic and medical evidence.
Kachelmann will remain in police custody until June 1, when authorities will review the situation.