We present multi-epoch near-infrared high-resolution VLT/NACO observations of the benchmark brown dwarf binary Kelu-1 AB. We have analyzed the first resolved spectra of the individual components. The primary itself seems to be an unresolved spectroscopic binary with spectral types L0.5+/-0.5 and T7.5+/-1, and the secondary is likely a L3 pec+/-1.5 with some remaining unexplained features. The obtained relative astrometric measurements over 3 years allowed an estimation of the orbital elements yielding an orbital period of 38-6+8 years and the first dynamical mass determination of 177-55+113 MJup. This total system mass is somewhat higher than the doubled upper mass limit for lithium burning and thus more than one would expect for a brown dwarf-brown dwarf binary system. Including a third component would solve this discrepancy.