I know @turbopsi has a series II, but in his last post he was actually quoting from the series III manual.
He understood the need to fit a battery switch between the Setec and the battery to switch the battery on and off. This is needed on a series II.
In a series III, the battery is wired directly to the Setec. No battery switch in that path.
The battery is connected and disconnected within the Setec and controlled via a simple switch.
One consequence of this is when this battery switch is on, the Setec charges the battery normally.
However, when the switch is off, it disconnects the battery form the loads BUT still enable the battery to be trickle charged at up to 0.8A.
@turbopsi correctly spotted the issue: If, in his case, he wired a Setec series II correctly with a battery switch between the battery and the Setec, how could the Setec possibly supply a trickle charge to the battery when the switch was in the off position? Of course if can't.
Here are the block diagrams of the Series II followed by the Series III: