One on each of 2 of the 3 phases to distribute the load when charging.
Also to secure some charging if bad weather knocks out a phase from the grid but not all.
Happens some times around here ^^.
Maxing them out to 75A per unit.
EDIT: Atm. at 48V (Roughly 12%) 15S cell config on the batteries). Will adjust further as needed.
Btw. if not visible: put an M8 nut under each of the 4 yellow screw tabs to ensure an airgap between the steel plate and the unit for slightly better ventilation.
The Devil is in the details ^^