Independent batteries are wired to separate terminals on the APS and internal diodes maintain total isolation between them. They are combined in a single output which is wired to the load.
Current is automatically drawn from the battery with the higher voltage. Isolation prevents the higher-charged battery from "dumping" into the lower charged or failed battery. Current is drawn "automatically" and continuously from the battery with the higher charge - no switch-over delay if one battery fails.
The unit is ruggedly constructed with heavy duty wiring studs and epoxy potted components in an anodized aluminum case. Wiring nuts, washers and mounting screws, provided.