Can someone post this on FIRST q/a

[Al Skierkiewicz]

Guys,
It wil be interesting how First responds to this question. The rules are not really clear in that they recommend the supplied connector as a minimum but indicate if you use something else you may not be compatible with other team's connectors. We use a Tyco/Amp connector that is available from Newark. It is designed for 100 amps, works well with #6 wire and looks like a larger version of the Anderson power pole connectors. We have used these for several years now. Remember to add mating connectors to your battery charger.

[Specialagentjim]

Originally Posted by Al Skierkiewicz

Guys,
The rules are not really clear in that they recommend the supplied connector as a minimum but indicate if you use something else you may not be compatible with other team's connectors.

We use the supplied connector every year and it's proven to be helpful during finals. When it gets down to that finals crunch, you want to have good charged batteries, and often times you run clean out. Luckily, sometimes you'll have an alliance that brings 20 batteries and has some amazing charging system devised. You borrow a battery from them for the match. Thats our thinking at least.

[DanL]

Originally Posted by Specialagentjim

We use the supplied connector every year and it's proven to be helpful during finals. When it gets down to that finals crunch, you want to have good charged batteries, and often times you run clean out. Luckily, sometimes you'll have an alliance that brings 20 batteries and has some amazing charging system devised. You borrow a battery from them for the match. Thats our thinking at least.

This topic has been brought up in a quite a few threads. In one of them, it was said that you can make a simple adapter with the kit connector on one end and your connector on the other.

[Venkatesh]

When we read the rules, we never got the idea that other connectors of different ratings were permitted. So, we were thinking of using two in parallel, mounting them in such a way that they would act as one unit.

If this would be allowed, it would be a great help.

[Al Skierkiewicz]

Originally Posted by Venkatesh

When we read the rules, we never got the idea that other connectors of different ratings were permitted. So, we were thinking of using two in parallel, mounting them in such a way that they would act as one unit.

If this would be allowed, it would be a great help.

That is actually a great way to double up the capability. The downside is the added weight. Make sure everything is tight and well insulated. I would like to see it if we are at a comp together. Come and find me if you can.

[Greg McCoy]

That would ensure compatibility with other team's batteries too. Good Idea!

[Joe Ross]

Well, FIRST answered no on the different battery connectors issue. The full response:

Section: 5.2.6 Status: Answered Date Answered: 2/12/2004
Q: <R20> May we use a different Quick Disconnect connector for the battery than the one provided in the kit? Specifically, we would like to use the Anderson Power Products SB120 (the next size up from the ones in the kit).

A: No. Use tie wrap to hold provided connector together.

Do you think they misunderstood the question, or do you think the ruling is no different battery connectors?

Venkatesh, you should probably ask about your method.

[ngreen]

Originally Posted by Specialagentjim

We use the supplied connector every year and it's proven to be helpful during finals. When it gets down to that finals crunch, you want to have good charged batteries, and often times you run clean out. Luckily, sometimes you'll have an alliance that brings 20 batteries and has some amazing charging system devised. You borrow a battery from them for the match. Thats our thinking at least.

Honestly, I am very wary about borrowing batteries from other teams after last year. We borrowed a battery from a local team for national and we ended up not moving one match because of a dead cell. That hurt us tremendously since it was in qualification. We ended up seeding like fourth or fifth but without a bad cell we could have easily been 1st. And you remember the number 1 alliance from Archimedes (wildstang, las guerillas, husky brigade). So I wouldn't completely trust a borrowed battery make sure you test it before, because when you're not moving, a minute and 45 second is a long time.

[Al Skierkiewicz]

This is a vast difference in policy from previous years. The rules specify "a" quick connect not "the" quick connect. Standby for further info.
We currently have 8-10 batteries, several chargers, four past year's robots and a prototype and robot from this year all wired for a different connector.

[Aidan F. Browne]

Al --

Please read the whole rule. The intent is that the connector provided in the kit is the connector that must be used. This is not an error.

"<R20> The 12v battery must be wired directly to a quick connect / disconnect connector (provided in the kit)"

As you can see, the rule clearly states that the connector is provided in the kit. The reason that the word "a" was used, is that there are two of the connectors provided (the entire connector is made up of two mirror-image halves).

Sorry to hear that all your previous equipment uses a different connector - but for 2004 the rule has changed.



Aidan

[Dave Flowerday]

Originally Posted by Aidan F. Browne

Sorry to hear that all your previous equipment uses a different connector - but for 2004 the rule has changed.

Do you happen to have any insight as to why the rule was changed? Using a different connector (assuming it's rated for at least the same amount of current as the provided one) does not cause any safety issues or add any unfair advantage that I can think of. This seems to fly in the face of the notion that the rules were going to be kept simple this year and that common sense should prevail. To me, this is like asking "Can we use #8 wire in place of #10?" and being told "no".

Rules like this would be a lot easier to accept if there was at least an attempt made at providing a reason.

Additionally, I read the passage from the manual that you quoted as "You need to use a quick disconnect, and there happens to be one provided in the kit." I don't read it as implying that it's required to use the one in the kit, but apparently that's what it meant.

[Venkatesh]

Could someone post a question related to my method on FIRST's Q&A? I won't have the ability to post that question for some time.

[Al Skierkiewicz]

Originally Posted by Aidan F. Browne

Al --

Please read the whole rule. The intent is that the connector provided in the kit is the connector that must be used. This is not an error.

"<R20> The 12v battery must be wired directly to a quick connect / disconnect connector (provided in the kit)"

Aidan,
I must disagree. The wording is not very clear but implying that the word "a" is meant to identify one half of a connector is a stretch. The phrase in parenthesis implies a suitable connector is included other wise it would read without parents. Although the wording of this rule has changed from last year, it's implication for veteran teams is that equivalent or better substitutes are allowable. I know that I read in the Q&A recently, a similar question was answered that FIRST recommended using the supplied connector and if a team used something different they risked incompatability with other teams should the need to share batteries arise. That question appears to have been removed from the Q&A as I was not able to find it this afternoon. Realistically, today's answer seems oddly worded in that the question seemed related to the connectors popping apart not replacing a kit part with something better.
I agree and it has been my stated opinion that the Anderson Power Products connectors work fine for most teams. There are teams that draw excessive amounts of current during match play that would result in heating, and fire using the 50 amp connector. A rule of thumb is any team that uses most or all of the motors including both drills combined with both Chips and/or both FP's will draw more current than the supplied connector can handle. You and I both know that the stall current on any one of these motors is over 100 amps.

[Biff]

Originally Posted by Al Skierkiewicz

Aidan,
I must disagree. The wording is not very clear but implying that the word "a" is meant to identify one half of a connector is a stretch. The phrase in parenthesis implies a suitable connector is included other wise it would read without parents. Although the wording of this rule has changed from last year, it's implication for veteran teams is that equivalent or better substitutes are allowable. I know that I read in the Q&A recently, a similar question was answered that FIRST recommended using the supplied connector and if a team used something different they risked incompatability with other teams should the need to share batteries arise. That question appears to have been removed from the Q&A as I was not able to find it this afternoon. Realistically, today's answer seems oddly worded in that the question seemed related to the connectors popping apart not replacing a kit part with something better.
I agree and it has been my stated opinion that the Anderson Power Products connectors work fine for most teams. There are teams that draw excessive amounts of current during match play that would result in heating, and fire using the 50 amp connector. A rule of thumb is any team that uses most or all of the motors including both drills combined with both Chips and/or both FP's will draw more current than the supplied connector can handle. You and I both know that the stall current on any one of these motors is over 100 amps.

This max draw is an issue, while testing on Carpet, with only the Cims installed in a full stall tank turn, (full left and right on the sticks). I mesuared 150 Amps on the negitive battery lead with a Fluke DC clamp on meter. I haven't tested with the drill motors on yet. I hope it can break traction or it will be a big rush for trick wheels.

[Aidan F. Browne]

Originally Posted by Aidan F. Browne

Al --

Please read the whole rule. The intent is that the connector provided in the kit is the connector that must be used. This is not an error.

"<R20> The 12v battery must be wired directly to a quick connect / disconnect connector (provided in the kit)"

As you can see, the rule clearly states that the connector is provided in the kit. The reason that the word "a" was used, is that there are two of the connectors provided (the entire connector is made up of two mirror-image halves).

Sorry to hear that all your previous equipment uses a different connector - but for 2004 the rule has changed.

All,

It is reasonable for you to ask for an explanation as to why you are being asked to use a 50A connector when you have experienced higher currents on your robots.

Here is the reasoning:

Anderson Power has been completely in the loop in selecting the connector for use in our application. They know what the specs are on the wires, breakers and maximum current draws. Anderson Power has determined that worst-case current draws do not exceed the true rating of the part.

Now - you ask - how can this be? Well - a commercial data sheet (in ~ 2 pages) tries to rate a part for use without knowing all of the conditions in which the part will be used. For this reason, data sheets are often very conservative. Once an actual application is studied - and all the environmental and usage characteristics are understood, parts are very commonly approved for use above their "rated" parameters. Time, frequency, temperature and other parameters all play into the "true" stress rating of a part. This is the case here.

To alleviate any of your concerns about a single SB50 connector carrying the entire current load for your robot, understand that in addition to Anderson's analysis of the situation, worst-case testing has been performed. Basically, tests have been run where a fully-charged Exide battery has been connected to the kit breaker through an SB50, and then the output leads downstream of the breaker were shorted in "crowbar" tests. The SB50 performed acceptably, was not overstressed and did not exceed its "true" ratings.

Now -- before you cry foul -- yes - there have been some part failures -- the worst known was the famed "WPI connector" from last February -- the picture of which has been widely distributed. That part was returned to Anderson and an extensive root-cause investigation was performed. It was proven that the reason that happened to that connector was that the two haves of the connector were only halfway connected and that there was only a point contact between the contacts. So - the failure was not because the part was overstressed, but that the part was not used as designed.

So - bottom line -- the Anderson connector is adequate for use on FIRST robots. There are over 25,000 successful uses of the connector in real FIRST matches. The 2004 rule is that you must use this connector. It is safe. The only concern is to make sure that you leave enough slack in your 6 AWG wire to ensure that you can properly mate the connector. It is also good practice to zip-tie the connector together each match to ensure it does not partially separate during impacts in competition (although this is not required).

Hope this helps alleviate the confusion and frustration.



Aidan