Unsafely securing Anderson connector?

[Andy A.]

During inspections at the BAE systems Regional, there was some discussion among inspection staff about Ziptieing the Anderson power connector (the red connectors used between the battery and electrical system).

The connector has been known to disconnect during matches from hard impacts. Many teams have gotten into the practice of securing the two parts of the connector with a ziptie.

One inspector pointed out that this is a possible safety concern because should there be a need to quickly disconnect the battery the extra time and effort needed to clip the ziptie might be to long to safely get the battery out.

Now, since the connector is underrated and there is at least one known case of it melting down, there is some weight to this. It would take longer to get the battery disconnected, especially if no one has a pair of clippers handy. But, how often does this come up?

Eventually, the suggestion to teams that ziptie was to rather use Velcro, but nothing was mandated.

My question(s) to all of you is; Does using a ziptie on the battery connector pose a safety hazard? Does the connector it's self pose a safety hazard/not suitable for our purposes.

-Andy A.

Originally posted by Andy A.
My question(s) to all of you is; Does using a ziptie on the battery connector pose a safety hazard? Does the connector it's self pose a safety hazard/not suitable for our purposes.

This is all the proof I need:

http://www.chiefdelphi.com/forums/sh...threadid=18079

[Jason Rudolph]

I would say no, after all, that is why the main breaker has to be in an easily accessible place on the robot, if you turn off the breaker, that is just as good as disconnecting the anderson power connectors. The connectors are just there to aid in easily changing out your batteries.

[Jeff Waegelin]

Originally posted by D.J. Fluck
This is all the proof I need:

http://www.chiefdelphi.com/forums/sh...threadid=18079

Is that a yes or no, DJ? I'd assume that means you think zipties are a safety hazard, but I wasn't sure...

When something like that happens, they are a safety hazzard..and they werent even zip tied

[Jason Rudolph]

Well, actually having them zip-tied might have actually helped to prevent something like this (I don't know if they were or not, but the tighter the connection, the better). Under high load, if the connector becomes slightly disconnected, then there will be an arc between the conductors, and viola, welded battery connectors!
Besides, if you are drawing enough current to cause the connectors to melt, then you certainly wouldn't want someone to try and grab that very connector to disconnect it, would you?

[Adam Y.]

Under high load, if the connector becomes slightly disconnected, then there will be an arc between the conductors, and viola, welded battery connectors!

Yeah arcing could have caused what that team experienced. It is a common way to also destroy motors because of the arcing inbetween the brushes.

Originally posted by wysiswyg
Yeah arcing could have caused what that team experienced. It is a common way to also destroy motors because of the arcing inbetween the brushes.

That is true, but if you noticed what Eric from FIRST said, how those anderson connectors are only rated for 60amps....yeah I know of teams that pull way more than 60 amps and could burn those connectors up like nothing.

[Joe Ross]

From the Rule book:

Although rare, the impact forces that robots sometimes experience during matches have been known to cause the Anderson Power Products connectors to disconnect. FIRST recommends utilizing a quick-release fastener, such as a Velcro strip, to hold the power connectors together during a match.

so, yes it is good to hold them together, but they specifically mention a quick release fastner, which a ziptie isn't.

[Dave Flowerday]

Wildstang hasn't used those connectors in years. We have a chart hanging in our shop that someone made a while back that graphs the losses through a few different connectors, and the loss in those red connectors in the kit are unbelieveable! We instead use Powerlock connectors which have much, much lower loss and are otherwise very similar. I believe they're also rated for more amps, but I could be wrong on that.

We've also never had a problem with the powerlocks coming apart. We don't use zipties or velcro or anything like that. I'd recommend them to anyone who's having problems with the kit provided type.

[Al Skierkiewicz]

As Dave has related above, we do not use the supplied connector. We use a similar Anderson product that is rated for 100 amps. The connector comes in pieces, the contact and a housing, that can be assembled in multiple contacts. When making the assy, the wire is first crimped into the contact and then soldered. All critical electrical connections are soldered.
Now before you get too worried, many teams use the supplied connector without problems. Although the connector is rated for 50 amps, it is used for short durations above it's design rating. Teams should check the connector, periodically for heating damage, bent contacts, or mating misalignment. The melting shown in DJ's pic above is unusual, but obviously does occur. I would ask DJ to elaborate on the conditions under which the failure occurred. Was it after a long practice session or while testing a new design, etc. If there is care taken in making the wiring between the battery and the main breaker then the breaker will adequately protect the battery and the robot from damage. With that said, a tywrap is good insurance for preventing the connector from coming apart, however there are better solutions. The velcro is a good one because it allows quick change of the battery during finals matches. You can't beat a secure battery mount, however, with short wires that are tied in place. The connector does not take any stress if all the wiring is secure no matter how hard the robot is hit or even if it turns over.

Originally posted by Al Skierkiewicz
I would ask DJ to elaborate on the conditions under which the failure occurred. Was it after a long practice session or while testing a new design, etc. If there is care taken in making the wiring between the battery and the main breaker then the breaker will adequately protect the battery and the robot from damage.

That happened to 190, the WPI team at some pre-season competition. Im not sure of the details, but they smelled smoke from what I heard and they took a look and it was like that. I think securing those anderson connectors is fine, but a zip tie could be hazardous if you need to break that connection for some reason or another

[Josh Hambright]

i would think releasable zip ties would work...
i think i have a secret stash of those somewhere.

[ahecht]

Originally posted by D.J. Fluck
That happened to 190, the WPI team at some pre-season competition. Im not sure of the details, but they smelled smoke from what I heard and they took a look and it was like that. I think securing those anderson connectors is fine, but a zip tie could be hazardous if you need to break that connection for some reason or another

It happened at the UTC scrimmage. All we knew is that our battery voltage on the OI suddenly dropped to 6.4 volts during one of our matches, and our robot stopped dead in its tracks. When it came back to the pit, there was a definate smell of smoke, but it took us a while to find the source.

We hadn't been overdriving the robot, but we did have one match every 15 minutes or so. Our battery was secure, and no stress was on the connector (although we did have our battery get disconnected in the next match because the replacement connector we used had wires that were too short). We didn't have any zip ties or velcro holding the connector together.

An interesting thing to note is that the connector was actually welded, and getting it apart required about five minutes, six different people trying, and four Leatherman's (and that is after taking it off the robot). Having a ziptie on there wouldn't have made it any more difficult to separate, and there is no way we could have sepatated it in an emergency (and we would've ended up with severe burns if we had tried).

If putting a zip tie on the connector could prevent this kind of thing from happening (assuming that the connector separated, causing an arc), I think it is a safty benefit, not a hazard. Besides, the circuit breaker is always there to open the circuit, if needed.

[meaubry]

Recent past experience alows me to validate that those connectors do come apart under certain impact circumstances. I'd have given alot for one at the Buckeye regional.
My advice: Tie wrap or velco wrap them and be sure to have with you a small set of snippers to cut them off afterwards. Tie wrapped or NOT doesn't assure the result from DJ's photo will or won't happen. If the connector does start burning up, tie wrapped or not - make sure you have quick access to the circuit breaker.