  We propose an analytical method to study the entangled spatial and spin
dynamics of interacting bimodal Bose-Einstein condensates. We show that at
particular times during the evolution spatial and spin dynamics disentangle and
the spin squeezing can be predicted by a simple two-mode model. We calculate
the maximum spin squeezing achievable in experimentally relevant situations
with Sodium or Rubidium bimodal condensates, including the effect of the
dynamics and of one, two and three-body losses.
