Battery Terminal problems

[Zack Briggs]

So we were at the Oregon regional this weekend, and we had an awesome time. We have a great robot, but we have a few issues we are working on solving before Seattle. One of the worst problems we have at the moment is the failure of our battery terminals. Our battery is situated on our robot (a shooting robot.) in a place where a lot of stress is put on the connectors from the battery to the robot. Although it did not happen often, a few times during the tournament our battery connections came loose and we ended up losing a match in the semifinals because of it. (My sincerest apologies to teams 1359 and 2122, I take full blame for that.) Anyway, if anyone has any advice on making the terminal connections stronger, from lengthening the wires to changing the size of heat shrink or anything else it would be greatly appreciated.

[Al Skierkiewicz]

Zack,
You need to be a bit more specific as to what actually failed. Many teams have problems with the hardware coming loose on the terminals of the battery. There are a few reasons for this. Never lift the battery by the wires as that loosens the hardware and cracks the battery terminal internal to the battery. You can eliminate the loose terminal problem by using a star washer between the terminal and the cable terminal you use. The washer prevents the two terminals from sliding past each other and that eliminates the hardware problem. (Use a star washer on the nut as well to keep it all tight)
If the Anderson plug pulls apart, just use a tywrap around the connector parts to prevent them from pulling apart.

[Zack Briggs]

Sorry if I wast clear, but it is the wire that is pulling out of the screw-in connectors we are using. We have never soldered them in and have had very few instances of the wore pulling out in the past.

[DonRotolo]

The only way to resolve the problem will be to eliminate the stress on the wires.

If something pulls on the wires - the way the bot is wired or configured, or someone lifting the battery by the wires - it makes no difference, the wires will come loose like Al S. wrote.

Making the wires longer might be one solution.

Don

[IndySam]

Buy some of these:




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The peace of mind they provide is worth much more than $15.00

[Alan Anderson]

Originally Posted by Zack Briggs

Sorry if I wast clear, but it is the wire that is pulling out of the screw-in connectors we are using. We have never soldered them in and have had very few instances of the wore pulling out in the past.

Did someone new install those connectors this year? There are two easy ways to do it, and only one of them is correct (the screw should not be putting pressure on the wire directly).

[Cascade]

We made our own cables by using hi current 4 awg hi strand count wire. Express Parts has the cable in real red and black. This makes the wire very flexible and much stronger. Next we crimped long barrel connectors on one end and the Anderson connector on the other end. You will need to get your hands on a crimper that can crimp this connector. Try going to a car audio place or find a mentor in the electrical field who may have access to one. Don’t forget the shrink tubing on the crimped connector end. Clean the battery terminals out to ¼”. Next go to Home Depot and get ¼” hex head (Allen Head) stainless bolts about ¾” long, star washers, and matching nylox nuts. And yes, carry batteries by the battery, not the pretty new cables.

This ended our battery cable problems.

[Zack Briggs]

Originally Posted by Alan Anderson

Did someone new install those connectors this year? There are two easy ways to do it, and only one of them is correct (the screw should not be putting pressure on the wire directly).

Well, that may very well be our problem. The screw in our lugs are just applying direct pressure to the wire I believe. What is the better way of doing it???

[Mike AA]

Originally Posted by Zack Briggs

Well, that may very well be our problem. The screw in our lugs are just applying direct pressure to the wire I believe. What is the better way of doing it???

The wire should go between the two metal plates, the part the screw is attached to and the part which goes to the battery. When the screw is tightened the wire is squeezed between the metal plates.



-Mike

[Al Skierkiewicz]

Zack,
Please look closely at the bitmap in the above post. Teams frequently do not strip enough insulation from the wire before insertion in this lug. At least 1/8 inch of wire should extend beyond the wire clamp before you tighten the screw. These types of lugs are not tolerant of a lot of movement in the wire. Many teams do not realize that you can route the wiring either straight up from the terminal or out to the side of the battery depending on how you mount the battery in the robot. Pick the orientation that is right for you. Once terminated bring the red and black wires close together and tywrap them in parallel. This will reduce the amount of flexing that takes place at the lug. Solder helps this type of connection. It does take a larger tip and at least a 35 watt iron. Remember to add a good amount of solder to the tip of the iron to help conduct the heat and then add solder to the end of the wire where it protrudes from the lug. Be sure that the wire and the lug are both melting the solder for the best connection. (Never tin the wire before you insert it in the lug.) Only add enough solder to the wire so that you just start to see it wicking under the insulation. If you use a torch, remember to remove the flame when testing the melting of the solder. Solder should flow freely after the torch is removed. If at an event, please remember there is no open flames allowed.

[Ziaholic]

In my experience, the trick with these connections is to prevent ANY movement of the cable, a few inches away from that clamped-end area.

We tied our cables down to the electrical panel to eliminate any sort of vibrations or cable movement from making that connection wiggle loose. Before we did that, it would wiggle loose EVERY time.

... and not only for this interface, but for every wire that goes to/from our terminal block assembly also ... same principle ... if the wires can move, they WILL wiggle out of those clamp-type connections.

[MegaSparks]

We had this same issue last year. The screw terminals were loosening during the matches. We found it the hard way similar to how you did. We ended up not being able to move real well and when we replaced the battery the problem went away. I have found the terminals will loosen during normal use and cause problems if they are not tightened after each and every match!

This year we went with the crimped terminals, as they are now allowed by the rules, and we do not have this issue. I suggest you do the same.