Chief Delphi - Battery Rules

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Re: Battery Rules

Quote:

Originally Posted by philso (Post 1542623)

Would a robot that is E-Stopped because it's battery bounced out while crossing one of the DEFENSES be considered a Tortola?

Tortuga, but yes - see my bolded sentence from Dr. Joe's definitions:

Quote:

Originally Posted by Joe Johnson (Post 1528125)

There have been a few legal eagles asking for the definition of what it means to be "tortugaed*"

It is a little like art, in that we'll know it when we see it, but a good working definition is that a robot is tortugaed when it stuck or disabled while attempting to traverse or helping another robot traverse a defense. Stuck should be broadly interpreted.

Some examples:

if you flip over crossing the Chapel of Frost and you're technically not in the defense zone anymore but everyone knows that it was the defense that done you in. Of course, we're going to give you a tortuga for that.

If the Drawbridge thwaps your battery from its cradle and the field officials don't disable you until they see you dragging that 17AmpHours Anchor around the courtyard, again, you've been tortugaed my friend.

If your alliance partner gets stuck on the rock wall and you go over to try to give them a bump to save them only to have their flailing Sally Port arm reach into your robot and, horrors, turn off your main breaker, why, that's a tortuga for two right there!!!

If you are holding open the Sally Port and an alliance robot goes insane, pushes you against that very door after which their motors start smoking and they hit their e-stop and you spend the rest of the match unsuccessfully trying to get out from the pin they've put you in. Again, two tortugas will be awarded.

I hope this clears things up, even as it maddens the legalist in the FRC world.

Cheers,
Dr. Joe J.

*Yes, it's a verb now.

Re: Battery Rules

Quote:

Originally Posted by rich2202 (Post 1542594)

Some people use "compression" to hold the battery (squeeze the sides of the battery). I personally don't like it. I would much rather see a strap across the top.

As an inspector, I would be highly reluctant to let a mounting like that through this season (or really any other, but particularly this season). A press fit battery isn't going to stay with the robot if you hit any defense in group B or D at speed.

The way I have looked at battery mounting is this.... Will the battery dislodge (fall out) if the robot is on one of its sides or upside down being shaken violently like another robot were trying to upright the tipped one.

If the answer is anything but no, keep working at securing the battery.

Re: Battery Rules

Quote:

Originally Posted by nighterfighter (Post 1542585)

If the batteries need to vent when charging, they are designed to do so while sitting vertically.

So, if one were to have doors on their battery cart, but also have the cart ventilated (with fans or otherwise) to prevent thermal runaway, it should be ok?

Re: Battery Rules

These straps are good for batteries.

I foresee more e-stops this year than last.

Re: Battery Rules

Quote:

Originally Posted by FrankJ (Post 1542592)

My preference is to charge upright. Truth is it really doesn't matter 99.9% of the time. My UPS has one of its batteries permanently upside down. The battery manufactures generally do not recommend this. Flat is OK. AGM & glass mat batteries have very little free liquid in them. Using a smart charger & charging at recommended charge rates is more important then battery orientation.

I would still charge upright if at all possible. Venting isn't really a concern with FRC batteries but gas pockets can be. At full charge ideally each cell has a plate of pure lead(Pb), one of pure lead oxide(PbO2), and sulfuric acid(H2SO4) as the electrolyte(in practice diluted with H2O). When you discharge both plates turn into lead sulfate(PbSO4), giving up electrons and creating more H2O. Sulfuric acid is completely soluble in water so that mixes just fine.

This is not true while charging. Hydrogen gas is created and there's a chance a pocket gets trapped against a portion of a plate that can't react with it. That portion doesn't charge, slightly reducing total capacity. Do this enough and you start real damage to the battery. This is negligible at trickle charge rates like a UPS sees, but we at FRC like to charge our batteries as quickly as allowed.