  Collisions electrically charge grains which promotes growth by coagulation.
We present aggregation experiments with three large ensembles of basalt beads
($150\,\mu\mathrm{m} - 180\,\mu\mathrm{m})$, two of which are charged, while
one remains almost neutral as control system. In microgravity experiments, free
collisions within these samples are induced with moderate collision velocities
($0 - 0.2 \,\mathrm{m\,s}^{-1}$). In the control system, coagulation stops at
(sub-)mm size while the charged grains continue to grow. A maximum agglomerate
size of 5\,cm is reached, limited only by bead depletion in the free volume.
For the first time, charge-driven growth well into the centimeter range is
directly proven by experiments. In protoplanetary disks, this agglomerate size
is well beyond the critical size needed for hydrodynamic particle concentration
as, e.g., by the streaming instabilities.
