  We investigate the coalescence factors $B_2$ and $B_3$ at low collision
energies ($\sqrt{s_\mathrm{NN}}<6$ GeV) with special focus on the HADES and
RHIC-BES experiments. It is shown that, in order to properly interpret the
coalescence factors $B_A$, two important corrections are necessary: I) $B_2$
has to be calculated using the proton $\times$ neutron yields in the
denominator, instead of the square of the proton yield, and II) the primordial
proton (neutron) densities have to be used for the normalization and not the
final state (free) protons (neutrons). Both effects lead to a drastic reduction
of $B_2$ and $B_3$ at low energies. This reduction decreases the discrepancy
between the volumes extracted from HBT measurements and the volumes extracted
from the coalescence factor ($V\propto 1/B_2$). While at HADES and low RHIC-BES
energies these corrections are substantial, they become irrelevant above
$\sqrt{s_\mathrm{NN}}>6$ GeV. The proposed correction method is model
independent and is only based on the measurement of protons, clusters and
charged pions.
