  We present twelve epochs of optical spectroscopy taken across the discovery
outburst of the black hole candidate MAXI J1803-298 with the GTC and VLT
telescopes. The source followed a standard outburst evolution with hard and
soft states. The system displays a triangular shape in the hardness intensity
diagram, consistent with that seen in high inclination black hole transients
and the previously reported detection of X-ray dips. The two epochs observed
during the initial hard state exhibited asymmetric emission line profiles,
including a P-Cygni profile simultaneously detected in H-alpha and He I 6678,
which indicates the presence of an optical wind in the system. The remaining
spectra, obtained during the transition to the soft state and the subsequent
decay, are instead characterized by narrower, double peaked emission lines
embedded into broad absorption components. One epoch (intermediate state) also
includes near-infrared coverage, revealing complex line profiles in the Paschen
and Bracket series, which suggests that the outflow is still present during the
outburst decay through the soft state. The growing list of low-mass X-ray
binaries with optical and near-infrared outflow signatures indicates that these
are common features. Furthermore, the lowest luminosity spectrum exhibits an
H-alpha full-width-at-half-maximum of 1570 +- 100 km/s. This, together with
previous constraints on the binary parameters, allows us to favor a compact
object mass of ~ 3-10 Msun, further supporting its black hole nature.
