View Full Version : Battery Flip-Flop...
Joe Johnson
07-03-2002, 15:39
I have heard that at the VCU regional, the officials are claiming only this year's batteries are legal -- not the ones from last year as was officially allowed via the Yahoo! board:
From Message #851
> Can we use different brand batteries other than exide?
A) The only batteries you can use on the robot are the exide
battery from this year's kit of parts or the Yuasa battery from last
year's kit.
From Messsage #661
> 2. Will batteries from previous years be allowed during the
> competitions? (assuming only one battery in system)
We have decided to allow Yuasa/Exide batteries from the 2001 competition to be
used, but not the green CSB or other batteries from prior years.
I have also heard that questions about chargers are also being raised, specifically, only the EXACT make and model that teams got this year are being allowed. If so, this conflicts with another Yahoo! message:
From Message #784
> Frcengineers:
>
> Rule C20 states that only the battery charger supplied or one with
equivalent
> specifications may be used.
>
> The charger manual indicates an output of 1 Amp hour, less than the
battery's
> capacity. We have some level of concern that this may be inadequate
for
> recharging during a match.
>
> Is it legitimate to use a charger of our own as long as its' output
does not
> exceed
> battery specifications? [For example, we have a charger that can
output 2 Ah
> in trickle charge mode or 10 Ah in quick charge mode.]
A) You may not use that charger. See rule C20. You may use another
charger that does not exceed the specifications of this years charger.
Please note that teams will be allowed to recharge their batteries in
the Pits overnight.
I hope that all this gets worked out before the competition starts tomorrow. We can easily suck a battery down to its dregs in 2 matches. If we have to get EXACTLY the battery that we got this year (i.e. not the Yuasa's we used last year and have several spares of as well), we had better order them NOW or we will not have enough batteries to get through the seeding rounds, yet alone the Elimination Rounds, which we hope to be in...
I hope that clearer heads prevail.
Joe J.
Matt Reiland
07-03-2002, 19:00
If we can only use 2 batteries and the charger that came with this years kit, we are sunk. I still can't figure out why the chargers from last year are banned?! We have 4 or 5 of them now and only one wimpy one from this year. If this ruling holds up we will be fed-exing more of the winpy ones and some more of this years battery type, what a TOTAL waste of our time and money.
I hope they come to their senses also
Andrew Dahl
07-03-2002, 19:36
we had our chager go belly up on us so unless we get an excat replacemtn will be be dead in the water by our fourth match
- they will not let us use last years chargers at all
dahl
Andy Baker
07-03-2002, 22:17
Originally posted by Joe Johnson
I have also heard that questions about chargers are also being raised, specifically, only the EXACT make and model that teams got this year are being allowed.
Joe J.
This is just great. (not)
We have looked for the past two weeks to find the exact same Exide model of charger, but we finally gave up. I found a pretty cheap charger (@ $18 each) that is the same strength, but from a different manufacturer... and we bought 6.
Sure, we couldn't use 6 if we had to, but I bet that we'll make friends if these are still legal.
We have also been going off of the rulings and notes from FIRST... it is way out of line for them to go against something that they allowed previously. If this happens I may just send FIRST the bill for our 6 chargers.
I'm assuming that this will be turned around and they will make sense of this... in time they usually make the right decision.
Andy B.
Kris Verdeyen
07-03-2002, 22:19
We have an issue with that as well. First of all, we have been trying (and failing) to find additional chargers. Does anyone know where some can be found?
I also think that the rule is foolish anyway. Has anyone given a reason for further limiting the chargers? Is it to ensure fairness to rookie teams who wouldn't have chargers from last year?
The trouble with this line of thinking is that everyone, including rookies, will have to buy more battery chargers and batteries in order to have enough power for their matches. So it's still lose-lose.
The only valid reason I could come up with is safety. If, for some reason, the less wimpy chargers were causing fires, or exploding, or threating people with knives, then that change to more wimpy chargers would be justified. But I haven't heard of any incidences of the above. (We did have a charger get ahold of an ice pick, though. - That was a mess.)
Andy Baker
07-03-2002, 22:33
Originally posted by verdeyw
The trouble with this line of thinking is that everyone, including rookies, will have to buy more battery chargers and batteries in order to have enough power for their matches. So it's still lose-lose.
Hmmm this is sorta like the mentality behind the Small Parts rule.
Originally posted by verdeyw
The only valid reason I could come up with is safety. If, for some reason, the less wimpy chargers were causing fires, or exploding, or threating people with knives, then that change to more wimpy chargers would be justified. But I haven't heard of any incidences of the above. (We did have a charger get ahold of an ice pick, though. - That was a mess.)
2 years ago at the Motorola Midwest Regional, one team blew up their battery by connecting the charger leads backwards... we had smoke, a few screams and scurrying people... it was kinda exciting.
Andy B.
Joe Johnson
07-03-2002, 22:37
Batteries from this year and last year are allowed (and presumeably batteries that are identical to this year's and last year's).
Chargers: Only this year's chargers are allowed or ones with 1 amp capability.
This is going to be very interesting...
Joe J.
P.S. Just for grins: What does YOUR batteries from last year and this year look like? I think FIRST shipped out a variety of batteries this year and last year. FIRST even has two different pitures of batteries in this year one says, "Yuasa." The other says, "Exide." By the way, NEITHER look like our kit batteries which are Exide brand but say, "POWERLIFT" on them and have a different model number than the ones listed in the manual! Last year, our kit batteries said, "Exide" on them, but, I saw a ton of batteries that said, "Yuasa" on them being used in the pits
I suppose that ALL the batteries I have that are the right model numbers OR look like the batteries we got in our kit or look like batteries anyone else got in their kits are legal. What do others think?
These are the images in the 2002 manual -- neither look like the battery we got from the 2002 Kit, not even the model numbers match.
http://www.chiefdelphi.com/pics/bin/1015559665exide.jpg
http://www.chiefdelphi.com/pics/bin/1015559615yuasa.jpg
Due to some nasty things that happened to our team we never even saw this years batteries or charger. So if we show up and can't use last years (or any year before that) were really in deep. I hope there is an official word on this soon so we can at least get ahold some something if we have to.
asher
Kevin Ray
07-03-2002, 23:18
Unless FIRST clears this up right now (well, yesterday), we're gonna have a whole lot of teams watching the final qualifying rounds when they're are supposed to be competing in them. This year more than any, we are using up the juice as fast as those batteries can put it out. Some teams said that they've been using up a fully charged battery in about three rounds with the loads they're drawing. This means that each team, especially those who make the finals, will have to have 4-5 batteries and the equivelant # of charges. As was said earlier in this thread, that causes EVERY team, rookie and vets alike, to buy more chargers and batteries--unnecessarily.
That especially amounts to big $$$ when we have to ship them to the nats and we will most definitely exceed the 400 lbs. allowed, thus, having to pay more money--which our team already doesn't have. :(
C'mon FIRST, don't leave us hanging!!!
Us to do is spend more money! I know this sound unreasonable but hey it could be happening that first didn't feel like spending a little extra on chargers and they found this great deal on the whipy once so they buy the whimpy once and make everyone use them
We had an enginner last year tape a 9.4V drill battery to the 12V battery charger to charge it faster. he let all the magic smoke out and now that battery dosn't work.
And he calls himself an EE....
Andy Baker
08-03-2002, 08:47
I just got an update from VCU. Steve Shade from team 7 just gave me a call with a battery issue update. (you da man, Steve!)
FIRST is allowing the old chargers to be used. The rookie teams are being asked to go out and borrow old chargers from veteran teams. It looks like 4 amp hour chargers will be allowed.
But...
Old batteries are not being allowed. Only the batteries from 2002 are allowed.
In special cases, 2001 batteries will be allowed... these are in cases where the 2002 batteries are no longer useable (blown up) or they have been stolen, or whatever.
Just as we thought... the officials at FIRST must've gotten a good night's sleep and made a good decision.
Andy B.
Joe Johnson
08-03-2002, 08:53
I have heard that last year's chargers are being allowed as well... so that makes it about as official as possible.
Concerning batteries though, do they really mean THIS YEAR's BATTERIES meaning only the batteries given out with the kit?
This is bordering on a "who's on first?" scenario!
Anyone with inside knowledge, do tell...
Joe J.
Who's on first? FIRST is on first. Who's on second? Dr. Who. No, wait Dr. Joe. I'm confused; and speechless!
combbat veteran
08-03-2002, 20:43
They are allowing last year's chargers to be used at a designated charging station at KSC. This years chargers may be used in the pits.
Have not seen any battery-gate at KSC. Either a lot of teams are using other year's batteries or FIRST gave teams many different types/colors. Even saw a red battery ??? Didn't look painted??
Few FIRST engineers at KSC regional this year. Most inspectors are volunteers that go by checklist alone. I expect this to be more common with more regionals meaning G. P. needs to be at an all time high.
Matt Reiland
08-03-2002, 20:53
We will be bringing all of our previous years chargers (~6) to both of the Michigan reigonals and we will be more than happy to help out teams that need them (as long as we get 1 or 2) this is a great day, I hate to run the robot on the 9V edge of losing communication it just gets too sluggish ya know.
Jeremy Davis
09-03-2002, 18:46
The main reason FIRST allowed last years chargers at VCU was because about half a dozen teams had chargers in various stages of disrepair. Unfortunately Spare Parts (the table I worked as a volunteer) did not have any spare chargers as of Thursday, so rather than leaving teams with no options, they allowed other chargers. We did receive back-up chargers around noon on Friday from FIRST, but they did not rescind the ruling that other chargers could be used. All that being said, I have no idea what this means for future regionals, but I figured I'd give some more information for speculation.
Curtis Williams
10-03-2002, 12:01
I keep hearing some people say we can't use last year's batteries. I went by yahoo post #851 and used last year's batteries at KSC. We had them sitting out on our table and noone said anything. This year's game is very power intensive and I think last year's batteries should be allowed.
As for the chargers - I can understand their concern for safety, but they should allow up to 4.3 amp AUTOMATIC battery chargers. The batteries are rated up to 4.3 amps, and the charges should be automatic for safety.
Mark Hamilton
14-03-2002, 21:10
Well we wound up (unintentionally) using old batteries now that I think of it, but didnt get called on it. As to the comment about the inspectors at KSC: We had to explain many of the points on the checklist to our inspector....
One of you EE types please help me out here (not the one with the 9V battery on the 12V charger, tho', thanks). Joe's battery photo shows the "capacity" of the battery as 17.2 Amp-hours. Now I know that a lot of hemming and hawing goes in to this rating, as far as discharge rate, final "discharged" voltage, and so on. But still and all, doesn't this rating basically mean that the battery will deliver about 1 amp at 12 volts for 17.2 hours before it's "flat"? Or about 17 amps for 1 hour? Or 34 amps for 30 minutes? Or 170 amps for 6 minutes? (Yes, I know there is a breaker that limits below that.)
Actually where I'm going with this is to look at the 1 amp charger. Doesn't it take a 1 amp charger 17.2 hours to recharge a flat battery with a 17.2 amp-hour capacity?
8 two minute matches at a sustained 60 amp draw is about 16 amp hours of energy draw, so one "fully charged" battery should in theory last pretty much through qualifying day. OK, so the 17.2 amp-hour rating says in the fine print that that is for a puny demand rate, maybe an amp or two, not for smokin' motors at 60 amps. I still suspect that the batteries are not getting nearly well enough charged on the 1 amp chargers in the time available.
Dodd
Terry Heath
16-03-2002, 21:11
Regarding these questions about batteries and chargers-- is the concern only for the qualification and elimination rounds? Can I take any comparable battery (different make) and use it during practice? I have a supply of batteries that I use for emergency ham radio communications and I intend for our team to use them during practice and robot work. We'll use only the supplied batteries and charger during qual. (and hopefully elimination rounds!). Thanks!
Rookie Team 847 from the rainy state of Oregon.
What battery you use only matters during "official" activities. I'd have a legal battery on board during inspections (especially at "weigh in") as well as whenever you're on the field.
Other than that I don't think anyone really cares, I know I don't. In previous years we've used unofficial batteries routinely in the pits and in the unofficial practice areas that spring up around the venue.
Speaking of which, if you want to make ALOT of friends, build yourself a 50 foot tether and let other teams use it for testing. Last year I don't know just how many teams used ours. After a while we got so tired of having teams come to borrow it we just left it in the practice area. Fortunately everyone was graciously professional enough to leave it there so we could pick it up at the end of the day!
Joe Johnson
19-03-2002, 09:25
As far as I am concerned, the battery issue is dead. FIRST has run up the white flag and surrendered!
I was very concerned about batteries and in particular only using "this year's batteries and last year's Exide/Yuasa batteries" (approximate quote). I wanted to know if the batteries I had qualified as last year's batteries (I was not sure which exact batteries in our stash were the ones from last year) and I wanted to get a ruling on using Exide's model "ES18-12" which is the replacement model number from Exide for the battery we have in the kit, which is model "EX18-12.
ANYWAY...
Bottom line: After much discussion and consultation, the official answer we recieved was "any 12V sealed lead acid battery in that size and shape is legal" (paraphrased, but true to intent).
So... ...that ends that as far as I am concerned.
Joe J.
Al Skierkiewicz
19-03-2002, 14:00
Dodd,
Here hopefully are some answers for you. The battery rating system is generally this...
Amp-hour capacity is what the battery can be expected to deliver when discharged at about 1/10 the rating. For our battery type, that is 1.72 amps for 10 hours before the terminal voltage falls to average of 10.5 volts. Please note that drawing more current reduces the overall amp-hour rating. Most robots that have optimized gear ratios and average drive efficiencies will not draw constant 60 amp currents for all two minutes of a match. Even the current spikes encountered when hitting stall conditions during the match will not trip the 60 amp breaker even though they are considerably higher than 100 amps. (The stall current for a single FP motor)
Now let's talk about our real world limitations. 8 volts minimum at robot controller, 45 amps sustained at any 30 amp breaker, 400 amps sustained at main breaker 450 amps at battery output max for very short periods of time.
The one to really worry about first is the 8 volt minimum at robot controller. Hitting this is a minimum 2 second dead time while it reboots, symptom is no rotating light for 2 seconds. (keep operator interface in voltage monitor and watch it!)
45 amps sustained at 30 amp breaker will trip this breaker even though it resets right away, symptom driving unstable, erratic behavior, noise from breakers tripping. (warning!!!don't touch a 30 amp breaker after a match where it has tripped repeatedly, it will be very hot!)
The main breaker should never trip under normal competition unless something is really wrong with robot design, wiring has failed or the breaker has taken a severe physical hit. (usually from the side)
Anyone who draws 450 amps from the main battery will have all of the above symptoms and melted wires, smoke, dead batteries and fried speed controllers almost every match and a host of other really bad problems. If any of these are happening to your robot please ask for help. We are bound by "gracious professionalism" to give assistance.
In the area of battery chargers, while it is ok to draw large currents it is not ok to charge at large currents. Battery manufacturer says "thou shalt not charge any higher than 4.2 amps" Using this charger on a cool battery that was fully discharged would take about 5 hours to full charge. Since no team can take a battery down to full discharge (robot controller reset at 8v.) most teams using a 4 amp charger should be up to full in 2-3 hours. 1 amp chargers will take 10-12 hours normally (over night) or 18-20 hours for fully discharged.
Any more questions, just ask. I will be going off-line while at Great Lakes starting tomorrow PM.
Originally posted by Joe Johnson
Bottom line: After much discussion and consultation, the official answer we recieved was "any 12V sealed lead acid battery in that size and shape is legal" (paraphrased, but true to intent).
Do you have a copy of the official answer in writing that we could bring to the regional, just in case?
OSHA wouldn't like this at all...
So FIRST is actually ADVISING that teams charge batteries overnight, eh? If you know anything about lead-acid batteries, you know that they release combustable gasses when charged. Well, lets make a situation here. There are regionals with sixty or so teams, right? Lets pretend that each of those sixty teams charges both of their batteries overnight, shall we? I'll bet dollars to doughnuts that the pit areas are swept by the college's janitorial staff, and I bet some of those staffmembers smoke while they work. OSHA, SAE, ASE, and many other organizations and almost all lead-acid battery manufacturers will tell you NEVER smoke near a battery, due to their gas discharges while being recharged. With all that combustable gas from 120 charging motorcycle batteries in the air, you can get a really not cool looking explosion. I'm sorry, but FIRST really should think before they print something as ludicrous as this.
Just a few words of sense...
I do believe that SLA batteries have a gas resevior (hence the sealed part), so no gas is actually released into the air.
The SEALED in sealed batteries means that you can't add fluid to the battery without damaging the case, it doesn't mean that gas cannot vent. The gas must vent or the case will rupture while charging. Trust me, an automotive service technician, they vent combustable gas into the air while charging.
Thanks for your thorough reply, Al. It reinforces my understanding of the situation:
A team relying solely on the two batteries and single one amp charger supplied in the kit this year is likely to have problems keeping their robot adequately powered throughout the two days of Qualifying and Elimination matches.
Dodd
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