SLU-70 Lugs

[Daniel]

Rule 48, Section 5.3.5, Electrical System Rules, page 16 and Inspection Item #28

"The ES-18-12 Battery, the Main 120 Amp Circuit Breaker, and the IFI CB/Distribution panel must be connected as shown in the diagram. The ES-18-12 Battery must use the Anderson Connector and the copper SLU-70 lugs provided in the Terminal Supply Bag. The Battery terminals and the SLU-70 lugs must be insulated with shrink tubing and/or electrical tape. You may use additional lengths of #6 red and #6 black wire to reach the panel as needed to make the above connections. The circuit breaker must be readily accessible for inspection and testing at each competition event."

Teams MUST use the SLU-70 screw lugs on all batteries used in competition, on main breakers and on distribution panel. Most teams missed this rule by not carefully looking at the diagram.

At the Great Lakes Regional competition this rule was enforced. The rule was explicit in the manual with accompanying diagram making their intent even more obvious.

Words of advice: “Strain Relief”. All mechanical connectors will loosen with movement. This includes screw lugs and crimp terminals. Somehow add strain relief to each lug by tie wrapping the #6 wire to the frame or some solid object to prevent any wire movement. Your robot is a moving, vibrating machine. Wire movements and vibrations can loosen any connection.

Check the tightness of the screw on the lugs between rounds. (I was told not to use Loctite on the threads - it acts as an insulator and releases when hot.)

FIRST tried to solve a repeating problem of improper crimps loosening by switching to the SLU-70 lugs. Few teams really know how to create a proper crimp connection. And pliers just don’t work at all (and I have seen crimps made with pliers).

The SLU-70 is an improvement that requires only a screwdriver to install instead of an expensive crimping tool. But you must remember that it is a mechanical connection and is prone to loosening without strain relief.

Strip off enough wire insulation so that the copper wire extends all of the way through the compression area of the lug for the best grip. If the conductor length is too short the jaws may not seat properly.

The advantage of the SLU-70 style lug is that the screw never touches the wire. Other type of lugs where the screw touches the wire do not make as effective of a connection for stranded wire. (We allowed this alternate style of connecter at GLR because it complied with the spirit of R48 and was still available.)

Be gracious and kind when you go to a competition… Take some extra SLU-70 lugs for other teams. We cleaned out both the local Lowes and Home Depot by noon on Friday. A number of teams gave out SLU-70 until their supply ran out – cudos.

Lead inspector
Great Lakes Regional