[Sergio]

Anytime you disconnect the batteries for more than a few minutes it causes the OBC to reset.

When the OBC is reset it will use a different algorithm to charge the batteries dV/dT for the first few cycles until it has enough information about the state of the batteries.

You need to allow those cycles to finish without interruption or the OBC will not switch to the energy counting algorithm, which does not take as long.

You need to make sure there is only a single pack negative cable and that the cable runs through the OBC hole in order for the OBC to measure current In/Out of the batteries.

Your batteries should be near 10v each at the end of the charge cycle while the charger is still running.