See other charge controllers
The new 40 amp MPPT Solar Charger Controller uses a set of dip switches to set the charge controller for each type of battery available.
This video will show the settings for the Master Slave setting as well for stacking 2 of these charger controllers to make one 80 Amp Controller.
Switch 1 : Battery Setting
Switch 2 : Battery Setting
Switch 3 : Controls Master / Slave