Using Second battery to Charge Tanks
 

Greetings,

After reading a "what do you do in between matches" tread, it seems like it is common practice for some teams to charge their air tanks with one battery, then swap out a fresh battery before heading to the field.


I have seen one post on the Q&A on this topic:

Here is R69 and the Blue Box:

So, is it legal?
I read this as one compressor and one battery mounted on your robot. Therefore, it would be illegal to change the battery after the tanks have been charged.

Am I reading the rule correctly?

Re: Using Second battery to Charge Tanks
 

Use battery one to charge the robot up, making sure that it is the robot controlling the compressor, not just hard wired or an external switch.

Turn robot off.

Remove battery and replace with a fresh battery two.

Go to field and compete.

Re: Using Second battery to Charge Tanks
 

As long as the "practice" battery is connected to the robot's electrical system via the red Anderson connector, and the compressor is connected to a Spike relay on the robot, then yes, you can use the practice battery to charge the air tanks and then swap in a fresh "match" battery before heading to the field.

If you powered the compressor DIRECTLY from the practice battery, bypassing the robot's control system entirely, that would not be permitted.

Re: Using Second battery to Charge Tanks
 

This is one of those rules I've always thought was silly. As long as teams are using the proper safety mechanisms, why does the ROBOT battery have to power the off-board compressor.

I've always seen nearly every team with an off-board compressor charge their system, THEN change the battery immediately before the MATCH.

1075 built a robotic cart years ago (it hasn't been used this year, due to malfunctions we haven't had time to fix). It runs an IFI control system, just like our 2000-2008 robots did, (its actually running the system from our 2004 or 2006 robot), uses Black Jaguars to control its drive motors (they're 24VDC motors), and has a separate 12V system to power the control system, and various 12V components, including lights, music, horns, etc (yes, we know musical carts in pits is a no-no, so we generally don't use it at official competitions). We also built a compressor onto the cart, with all the proper interlocks (pressure switch shutoff, etc) but in recent years have not been allowed to use it to pressurize the robot. (We've still used it for blowing metal filings away, and blowing up trackballs)

It gives absolutely zero competitive advantage, and I don't understand why we're not allowed to use it, since its equally safe.

Re: Using Second battery to Charge Tanks
 

This is why. The inspection checklist also specifically says the off board compressor MUST be powered by the ROBOT control system.

Are there other safe way to pressurize the system? Yes. But having everything controlled by the robot control system makes things go much smoother for both team and inspectors.

Re: Using Second battery to Charge Tanks
 

It's sort of a second-level requirement. The system providing the pneumatic pressure must be inspected to verify that the pneumatic system of the robot complies with the rules. To make that inspection practical, the compressor must be controlled and powered by the robot. It would not be reasonable to ask inspectors to vet any random pressurization system that a team might choose to use.

Re: Using Second battery to Charge Tanks
 

...The ROBOTs are required to have the regulators, and the relief valve regardless of whether the compressor is on or off-board. They're also required to have a High-side gauge. I'm failing to see how the method of getting the pressure there matters. Have the team pressurize the system during inspection using their method of choice, see that the system they're using shuts off when the robot reaches ~120psi (as they already do now) and voila.

Realistically, theres only 3 compressors on the market (at least, widely known to the FRC community), that are legal anyway. Its easy enough to check if the compressor being used is one of those 3 (The old Thomas KOP unit, The Viair 92C (new KOP) and Viair 90C.

Frankly, if the compressor is not physically on the robot, I don't see why it matters what compressor you use. A higher flow rate compressor means it fills faster, but if you're not generating the compressed air during the MATCH, who cares, its not giving you any advantage because you have a finite amount of air storage on the ROBOT.

Re: Using Second battery to Charge Tanks
 

You seem to be missing the point here.

Its makes the inspection process 10x easier. If every team has to provide spec sheets proving that their non KoP compressor meets the required specs, you can be certain that there will be many more problems/headaches for teams. FIRST says this is a rule, so just accept that fact. I had to help at least 2 teams reconfigure their pneumatic system simply because they didn't read the rules this past Thursday.

Re: Using Second battery to Charge Tanks
 

I understand that's how it's done, but is it legal?

A robot is one compressor and 1 battery. By using two batteries you are effectively using more "electrical energy" than is available in one battery. This is what I am questioning.
When I was asking about off board compression, I was told we had to use the same battery as we would use in the match. Why is keeping the compressor on the robot given an exemption to that rule?

Re: Using Second battery to Charge Tanks
 

I assume you asked the GDC in a Q&A not some random volunteer.
Remember, even answers from the Lead Robot Inspector may change as the season progresses and they all come to a common rules interpretation.
I don't recall any such Q&A though.

I think your issue here is how the question is framed and (presumably answered by the GDC).

The answer you received appears to simply be addressing the issue that the compressor must be powered through the robot by the robot battery whenever it is operated, not that batteries cannot be changed.

The robot can only be powered by a single battery while in a match.
A match doesn't begin in the pit or on the queue or in a previous on-field appearance where pressure wasn't releaved afterwards.
A match begins when the field sounds.

Re: Using Second battery to Charge Tanks
 

And that is the question I think is core to my problem. When does the robot become the robot?
From my POV once you use the battery to compress air in your tanks, that battery becomes part of the robot for that match. If you removed the battery after the compression, you are using two batteries for a match.

Mark,
The question regarding swapping batteries was asked in the Q & A and they directed the petitioner to R69. I'm just not sure how that answers the question.

Re: Using Second battery to Charge Tanks
 

Then I posit that you cannot change your battery after you have used the energy to download any code that will be used in said match. :)

Re: Using Second battery to Charge Tanks
 

I would disagree because changing code does not store anything that could do work for the robot. :]
Thanks for being lighthearted about this. This is not a hypothetical for my team. With such a large set of tanks this year, it take over one minute to charge our system. If we could do that with another battery it could be a substantial advantage for the team. I just don't see how it jives with the rules. I know others do it; the GDC is rather vague on the issue. I just don't like gray areas. It get's folk in trouble and feelings hurt.

Re: Using Second battery to Charge Tanks
 

Probably should just use the same battery you used to image the cRIO last. :p

Re: Using Second battery to Charge Tanks
 

I don't believe any rule supports your self-imposed position.
I don't beleve the GDC supports your position, otherwise, they would say so.

I believe only one battery can be used during a match.
A match begins with the field sound and ends with the refs all clear flag.
(it doesn't end with a field sound this season).

I don't accept the stored energy argument (even without the evidence of a rule), otherwise, springs, elastic tubing and other potential energy storage is also suspect. Thereby excluding human muscle power from the robot, as well, if the battery is the sole source of energy.

My beliefs don't constrain the GDC, but are what I will advise any team that asks.

I'm rooting for your students.:)