Check your Anderson battery connectors

[thinker&planner]

We had an entirely different problem. Two matches in a row, our battery connector actually separated from the connector on the robot. Both times, it happened after going over the rock wall the second time.
The part that bugs me the most is that we had hours and hours of practice, and this never happened. Also, the connectors on those batteries and the one on the robot were properly constructed, and they are just as hard to pull (wiggle) apart as those on any of our other robots.

The first match, when we pulled the robot off the field, we wiggled the connector and the robot turned back on.
The second match, everyone on the drive team checked to make sure the connectors were properly seated. When we pulled the dead bot off the field, the battery connectors were at least 3/8" away from being fully seated.

Being dead for two of nine matches really sucks. Fixed by zip tying the connectors together.

[Doc Wu]

Originally Posted by thinker&planner

Fixed by zip tying the connectors together.

I have been told for years that the SB50 connectors should be zip-tied together, but still don't quite agree.

If you find the connector pulling apart, SOMETHING is doing it. It won't happen spontaneously.

Your wires may be too short and/or your battery may be moving around within the robot. Both are problems that should be corrected by something other than adding a zip tie.

Someone always says "I've seen matches where the battery fell out and was dragged by the power cables across the field." If that happened, I'd rather have the connector come apart and disable the robot. You're going to get an E-stop anyway.

If zip-tying the connector makes a problem go away, you are really masking the problem. You have something wrong with the connection. The SB-50 connectors are very reliable and are designed for exactly this purpose.

That doesn't mean they can't fail, but failure is usually due to wear, mis-assembly, or abuse. You can't take them for granted. You need to check them and spot any potential problem. It all comes down to attention to detail.

The fact that they come pre-assembled doesn't mean that one can't be mis-assembled. The mating surfaces inside can be scratched and pitted by connecting things with clip leads, etc. (This is why the rules now state that battery chargers must be fitted with a matching SB-50 connector.)

[rammsey]

Originally Posted by Doc Wu

I have been told for years that the SB50 connectors should be zip-tied together, but still don't quite agree.

If you find the connector pulling apart, SOMETHING is doing it. It won't happen spontaneously.

Your wires may be too short and/or your battery may be moving around within the robot. Both are problems that should be corrected by something other than adding a zip tie.

I myself, along with the other drive team member when we put the robot on the field. Checked the connection, tugged on it, wiggled it. It was seated in there for good. We made sure it was not going to pop out like our previous match.

But then we go over a rock wall (not even at full speed if i remember correctly!) and boom, out for the whole match.

Back in the pits, we tug on it, wiggle it around, bend it, do everything possible. Drop the robot from 5 inches multiple times. Nothing! D:

Nothing like this has happened during any practice where we basically bashed the robot into defenses every which way.

Like you say, there maybe an underlying cause, but I guess we have to wait till our next regional to do further inspection. But even if we do fix the issue, definitely still going to use zip ties, can't risk it.

[philso]

Originally Posted by rammsey

I myself, along with the other drive team member when we put the robot on the field. Checked the connection, tugged on it, wiggled it. It was seated in there for good. We made sure it was not going to pop out like our previous match.

But then we go over a rock wall (not even at full speed if i remember correctly!) and boom, out for the whole match.

Back in the pits, we tug on it, wiggle it around, bend it, do everything possible. Drop the robot from 5 inches multiple times. Nothing! D:

Nothing like this has happened during any practice where we basically bashed the robot into defenses every which way.

Like you say, there maybe an underlying cause, but I guess we have to wait till our next regional to do further inspection. But even if we do fix the issue, definitely still going to use zip ties, can't risk it.

When you drop and bash your robot, you can only determine that you may have some loose connections. You will have a hard time determining which connections are bad by doing this. To find the bad connections, you really need to methodically check each and every connection point, starting from the terminals of the battery, to look for loose connections. Do not stop if you have found one loose connection. It is quite possible that you have two or more. You also have to treat the crimp of the contact in the connectors as a separate connection point to be checked apart from checking that the contacts are actually connecting. You seem to be focusing only on the battery connectors.

[rammsey]

Originally Posted by philso

You seem to be focusing only on the battery connectors.

Because that's what our problem was 2 of our matches.

After each of those matches, when going to take the robot off the field, you could see that the battery connector was not seated in right. Even though before, like I had said. We made sure it was in there properly.

Rest of our matches we used zip ties so there was no chance of it getting unseated and we had no issues.

We just can't seem to figure out how that connector could have come loose going over rock wall those two matches.

[Ether]

Originally Posted by rammsey

We just can't seem to figure out how that connector could have come loose going over rock wall those two matches.

How is your battery secured??

[thinker&planner]

Originally Posted by Ether

How is your battery secured??

Here's a bad picture, but it's the best I could find.

There is velcro strapping holding the battery down into a "box" of sorts. In neither of the two matches where the connector separated did the velcro become undone. It's pretty hard to get the battery in and out, you could even say that it's a "press fit."
All of our battery leads are that long, so the battery would have to be launched up 6 inches to pull the connectors apart.


The best theory that I came up with is that it has something to do with the robot-side connector being bolted solidly to the frame (the "attacking side" that hits the defenses before anything else.)

[Ether]

Originally Posted by thinker&planner

Here's a bad picture, but it's the best I could find.

Thank you, but... please use JPG for photos, not PNG.

[rammsey]

Originally Posted by Ether

Thank you, but... please use JPG for photos, not PNG.

Any reason why? I don't see anything wrong with using PNG

[Ether]

Originally Posted by rammsey

Any reason why? I don't see anything wrong with using PNG

Here's the reason:

[rammsey]

The only difference is file size, and the difference between them is ~600 KB, which is negligible.

I'm still failing to see what's wrong.

[philso]

Originally Posted by thinker&planner

Here's a bad picture, but it's the best I could find.

There is velcro strapping holding the battery down into a "box" of sorts. In neither of the two matches where the connector separated did the velcro become undone. It's pretty hard to get the battery in and out, you could even say that it's a "press fit."
All of our battery leads are that long, so the battery would have to be launched up 6 inches to pull the connectors apart.


The best theory that I came up with is that it has something to do with the robot-side connector being bolted solidly to the frame (the "attacking side" that hits the defenses before anything else.)

The pictures really help people understand your situation.

The loops in your battery cables are long enough that the movement that is possible should not cause a good pair of connectors to come apart. How much force is needed to pull them apart? Try pulling at different angles. I don't see where your bumpers end up. Is it possible that another robot is hitting the battery wires? It seems that the constant in this is the connector on the robot side. Have you tried replacing it? Try putting painters tape so part of it is on the battery and part of it is on the bracket. Put other pieces so they are on one of the battery wires and the frame next to it. If anything is moving more than a few millimeters, the tape on it should tear and give you some clues.

[rammsey]

Originally Posted by philso

How much force is needed to pull them apart? Try pulling at different angles. clues.

We tried tugging on it pretty hard, and at all different angles. It is not at all easy to just pop that connector out.

Originally Posted by philso

I don't see where your bumpers end up. Is it possible that another robot is hitting the battery wires? I

The inside of the bumper comes right up against the outside face of the aluminum on the other side of the connector. Sorry if I'm not explaining it properly, we don't really have good pictures.

And both times the connector did dislodge, it happened during the second (this really baffles us) crossing of the rock wall. So no robot was hitting the connector at the time.

[philso]

Originally Posted by rammsey

We tried tugging on it pretty hard, and at all different angles. It is not at all easy to just pop that connector out.

The inside of the bumper comes right up against the outside face of the aluminum on the other side of the connector. Sorry if I'm not explaining it properly, we don't really have good pictures.

And both times the connector did dislodge, it happened during the second (this really baffles us) crossing of the rock wall. So no robot was hitting the connector at the time.

Have you tried installing the battery and putting the Velcro strap on then try lifting the robot by lifting the battery? Perhaps the battery is "jumping up" and stretching the Velcro strap then popping back into position during the violent manoeuvre.

At Bayou yesterday, we popped our PDP panel off and separated all the Anderson connectors to our motor controllers when we hit the Portcullis too hard. It was stuck on with two long strips of Duo Lock which holds more strongly than Velcro. We (and others) have broken things that have never broken before.

[adciv]

We've had a few issues with the contacts separating slightly woke the connector was mated. One of these was supposedly from the contacts having come off the retaining clips (not sure how, but I've seen this before on our battery charger ). On the other, if I rotated the wire, then the contact also rotated in the connector. We've instituted an inspection since they on order to catch these and I've had some spare cables made up on case we see more. I think we're starting to see aging issues with the wiring. These connectors are mated and unmated frequently and may be wearing out the housings and contacts.