[Sergio]

There is an SCR device between the negative input and output of the OBC that controls the charging current.

The OBC does not look for any certain voltage to tell the charger to turn OFF, it uses the information it collects during discharge and it measures the charging current as it charges to make sure the pack energy has been replenished.

When the OBC is reset by disconnecting the batteries for more than 10 minutes, the information it holds for the energy removed from the pack is lost from its volatile memory so it cannot use the coulomb count charging method.

The first few charge cycles after the OBC is reset uses a dV/dT algorithm and tries to create a pack health "profile", once it thinks it can properly estimate the overcharge needed to bring the batteries back to full SOC it switches back to coulomb count.

In either case the charger will always come ON in "bulk phase" at full current and when the pack voltage gets to about 57v, the OBC starts to reduce the current and switches to the "Absorption phase" until it determines the pack has been charged, that phase can go up slowly to 65v or last 16 hours.

You mentioned the OBC and batteries are new so make sure there is nothing connected to the batteries (accessories, converters, etc) that may be affecting the OBC dV/dT calculations.