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Can someone confirm what the current state of play is with lipo batterys in heavies? Why aren't they able to be used when they have been well proven in featherweights to be a stable battery that can take abuse and still not burst into a hot flaming mess?
I ask as I'll be looking to buy batteries for Smidsy in the near future and don't want to waste my money on A123s if I can go ahead and use lipos.
from what i've heard in other threads big nipper is testing them for heavyweight combat and they'll go from there
Good point bringing that up Gary. Big Nipper are testing them, but I also remember reading that THz was testing them too, and that must be 2 years since that information was posted, so its probably time to release their findings and update the rules accordingly?
I haven't heard of Big Nipper exploding recently so presumably the tests are going well.
I've been quite vocal in my opinion, and it hasn't really changed.
I'm very uncomfortable with them, considering the environment we work in, a leisure centre, it'll take one HW fire and then we've got issues. A pits full of hw's with lipos is a scarey thought !
The FRA were supposed to be getting a set of lipos to destroy so we could see an actual fire, but it never happened. I've seen videos and they are scary.
I don't know Alans actual view, but I know from what we've spoken about he feels the same!
Maybe he could shed some light on his views.
The other issue I have is the event organisers will have to decide who can and who can't as I wouldn't be comfy with some people using them.
In the couple hundred featherweight fights that have taken place in the past couple years with lipos present there has yet to be any kind of incident and those featherweight fights have been far more intense than anything I've seen from heavies in terms of collision speeds and energy involved.
The power requirements in terms of burst draw current in featherweights is generally far higher too and again, no issues.
I do have concerns. As Jonno said it will only take one incident, and that will be it, they would just get banned on the spot, so anybody running them would be stuffed, and thats best case scenario.
I disagree regarding featherweights being in more extreme conditions.
If they were to come in as a legal source, before attending any event the tema must declare what setup they are using. I can just see people buying cheap ebay packs and throwing them in a heavyweight.
As for the argument that all betteries have a risk, of course they do, but in 10years i haven't seen a single lead acid battery fail in any sort of dangerous way. When NiCads/NiMhs go up, they just smoke and can be got outside quickly. The issue is the LiPos produce a flame, this is a risk to everybody and to equipment/arenas/venues.
As for Big Nipper running the tests, they started at the beginning of the year, and at the end of the year it will be passed to the FRA whether they want to put them in the rules or not. I agreed to them allowing to test the LiPos as they were looking for new batteries and were willing to spend the money on them and run the tests. They are a team that have used Lipos for many years in the featherweights (and in probably the most extreme FWs). Big Nipper is an ideal robot to test them as they have a high power usage (Mag 4/8wd and electric weapon) and if anything did happpen it will be in the most secure robot.
Everything we do is a calculated risk, i think Lipos are one that we don't have to take. I don't see any issues why teams wouldn't want to run A123's they have proved themselves.
I think, I being a risk averse type of person, would agree with Alan and Jonno regarding the introduction of LiPo batteries in heavyweight robots. Even if the FRA approves them the EO's could say No thanks at my events.
From A safety perspective it is all down to control of risk for instance the Big Nipper team can run LiPo batteries in Big Nipper safely because, they are fully trained engineers with high quality equipment using the batteries in a fire proof type custom aluminium case, fitted to a titanium armoured robot! but what about the people from other backgrounds that don't have the knowledge or funds to run them with the same safety considerations. (Don't get me started on the high pressure gas equipment fitted in the robots these days.)
Either people have to be trained to use these potentialy dangerous things safely, or they are should be left to the flying set. :!:
It's a hobby guys, let's not kill anyone!
Stored CO2 is just as dangerous if not more so than a battery fire but I can see I'm hitting my head on a brick wall here trying to get them brought in :|
Does it even matter if the FRA approve them then?
Your not hitting your head against a brick wall at all, we are talking about this.
As event organisors when we go to a venue and we talk about the risks, and go through our risk assesment they think robots are dangerous enough without a pits full of batteries which could go up in flames.
My issue isnt with big nipper using them, or even you using them, its when we get to the stage like we have with fw where it is now a standard to use lipos.
Then we have increased risks, and potential for people which shouldnt be using them, to be using them, or even people which can use them make a mistake.
How is stored Co2 just as dangerous?
what about li-ions they are lipos with a harder case aren't they?
as for co2 how many hits from bots like inertia and drumroll could a.fire extinguisher take we all saw raizer blade explode when its gas tank was punctured. it exploded
little hitter would turn a paintball bottle into a collinder
I am very inexperienced but I.see.no.reason why a well protected robot with loads of armour andna.fireproof box won't do the job
sorry for all the full.stops.
Do you mean the uncontrolled release of potential energy, from a catastrophic failure of a cylinder of liquefied gas at about 1000 psi.Quote:
Originally Posted by roamingrobots
The potential energy to flip a 100kg robot over 2 meters into the air about ten times with all the losses in the system.
The continual charge and discharge of said cylinders at below normal temperatures
The manufacture of expansion vessels with no regard to certification for the gas handling equipment
The said cylinders being held in place with cable ties!
Anyway I said don't get me started :proud:
Craig ,
You mean we won't be seeing a full pressure Co2 saint soon ?? :proud:
If a co2 bottle gets damaged or fails in a robot in the arena in a fight, all that will happen is it expels the gas. No issue there.
If a burst disc blows, it expels gas, and generally bottles are kept inside the robots. Burst discs ONLY fail when people don't follow safety procedures and overfill a bottle anyway.
The worst case scenario is when filling bottles, where users are up close.
Fire is a whole new ball game !!
It's similar to why we don't use petrol, we manage the risks in the environment we work in.
I'll put it out there, even if the FRA ok them at the end of the year, I don't believe I will be allowing them to become the norm.
As a business, the rewards don't jump in leaps over the risks, it's unneccisary in my opinion when A123's are around.
John
That's right Jonno I don't feel I could make one I would be happy with at the moment.
But I must stress this is only my opinion and I am not trying to influence anyone in an adverse way.
I think I am A victim of my own training ,we were told never mess around with compressed gas, always use the correct fittings never modify or use a gas handling component outside of the manufactures instructions, and so on and I just can't shake that!
With the fire risk question I would agree this dose cause problems with regard to Insurance and public safety. These are questions that have to be addressed in a legal way, rather than from an engineering point of view.
The CO2 comment was based around what Craig mentioned earlier but I digress.
I guess that's me got my answer, no point in buying them even if FRA allows as EO's won't allow them to be ran.
So where is everyone getting their A123s? All I can find are cheap chinese knock offs
a.fuse wouldn't.help.short circuiting would.it.
well yes it would and those are already in the rules. The issue is if they are punctured however if they are properly shielded in a bot this shouldn't be an issue.
Is it a problem if a heavyweight robot catches fire in the arena?
Is it a problem if the arena is filled with a cloud of white smoke?
...yes...
http://www.electricwingman.com/power/a1 ... cells.aspx
On the safety issues I think quite a few of us should be taught how to fill gas , charge safely and be as safe as possible.
is 2300mah enough? 3 packs of 12v?
viewtopic.php?f=104&t=5092Quote:
Originally Posted by terry
try here :wink:
LiPo trials for heavyweights were announced at the AGM this year. Minutes from the AGM are available on the meetings page.
Despite the obvious advances in the technology there remains a very real risk of fire following abuse. However, experience in featherweights has shown that this is highly unlikely. These risks are also easily managed with the use of LiPo bags and chargers with built in balancers.
Whether this scales safely with heavyweights is currently under scrutiny.
If that is your answer to both questions, go to a less unsafe hobby. I can recommend basketweaving.Quote:
Originally Posted by psycho_fling
1) The TV series had a Firepit and Sergeant Bash, Growler had a flame-fart weapon. I believe it was intended to get competitors on fire. Didn't work well.
In 2001 I was using HDPE as armor on Project One. I tested the flame resistance of that rather nice fuel (one of the cleanest solid fuels known to mankind) with a oxy-acy torch. Took ages to get a 12mm plate burning.
Also, short out a good SLA, and the wiring will burn... Burning plastics, Goodygoody.
Short out a bad NiCD with low internal resistance, and you get a cadmium laced smokescreen...
2) Why do event organisers sometimes augment the arena-effects with smoke generators?
For a heavy... Depending on motors, wheelsize and gearratio.Quote:
Originally Posted by mattsdragons
TAN draws about 4.5 Ah from an affordable 36V 9Ah SLA pack during a normal fight. The edge of the capacity of such a set. Bosch 750, big wheels , gearratio 20-1+
Gravity III did about the same, with a Bosch 750, 36V, 20-1 gearratio to 10 kartwheels.
LiPo is a tad more efficient; So a 9S 7000mAh 30C pack sounds perfectly doable for a 2WD machine.
As the smoke from lipo's is toxic the answer is yes to both of these.Quote:
Originally Posted by maddox10
The issue here to my mind is that there is a very small risk of this happening BUT if it does then there's no way of stopping a lipo fire until it's burnt itself out. You can put the remaining flames out after its finished but the initial fire will happen once started and each cell will go individually.
Lipo fires are rare and fuses will actually stop the vast majority of those which are thinking about happening. Consequences are quite high. When you do a risk assesment you have to balance the probability and the consequences.
The fire is not sustained by the usual influences such as heat, fuel and oxygen. It is a chemical reaction which once started will not stop until it has finished doing its stuff.
Arenas by their very nature (contained boxes) are not easily ventilated so if it does happen the fumes hang around for a while. As they're full of heavy metals and stuff they're not nice and the 'poisonous' effect is cumulative.
I think the testing will show that lipos can be used safely in a well constructed machine. I also think we need to test some of these to destruction to see how effective safety measures are by introducing heat, piercing some of them, exposure to shock etc etc.
Also we need to get on top of how age and deterioration increases any risks etc. Over time the internal resistance increases which means the heat produced in every fight increases the risk of it happening. That being the case, how do you monitor that?
With stringent rules these could be safe but more research needs to be done but we also need the plan of how to clear them up if they do go.
And is it more toxic than NiCD smoke, or even the smoke from burning insulation?Quote:
Originally Posted by widow_twanky
I know. A part of my job too.Quote:
Lipo fires are rare and fuses will actually stop the vast majority of those which are thinking about happening. Consequences are quite high. When you do a risk assesment you have to balance the probability and the consequences.
Not true, any chemical reaction can be stopped.Quote:
The fire is not sustained by the usual influences such as heat, fuel and oxygen. It is a chemical reaction which once started will not stop until it has finished doing its stuff.
For Lithium
Remove any oxygen -even in bound form- and the reaction stops.
Remove all heat- and that's difficult, as lithium will reduce CO2 to carbon and oxygen, generating even more heat-
That is why any containment is used for things like painting cars, working with radioactive materials and so on. It's called a ventilation system with filters....Quote:
Arenas by their very nature (contained boxes) are not easily ventilated so if it does happen the fumes hang around for a while. As they're full of heavy metals and stuff they're not nice and the 'poisonous' effect is cumulative.
We just need a budget for that.Quote:
The issue here to my mind is that there is a very small risk of this happening BUT if it does then there's no way of stopping a lipo fire until it's burnt itself out. You can put the remaining flames out after its finished but the initial fire will happen once started and each cell will go individually.
I think the testing will show that lipos can be used safely in a well constructed machine. I also think we need to test some of these to destruction to see how effective safety measures are by introducing heat, piercing some of them, exposure to shock etc etc.
And I suggest we test a worn out max-power pack (37V 20Ah ) in a thin HDPE foam filled box , lets see how fast that ignites
Rather simple, good chargers do it on their own.Quote:
Also we need to get on top of how age and deterioration increases any risks etc. Over time the internal resistance increases which means the heat produced in every fight increases the risk of it happening. That being the case, how do you monitor that?
You can make the rules foolproof, but then mother nature will appoint a better fool.Quote:
With stringent rules these could be safe but more research needs to be done but we also need the plan of how to clear them up if they do go.
The smoke from a nicad is probably not worse than that from a lipo but posionous smoke is posounous smoke so not worth debating cos if it kills or seriously injures someone it's has the same relevance. As far as burning insulation is concerned you can get 'low smoke, zero halogen' insulation on cables but it's probably not worth it. The problem i see is in the amount of smoke produced and the speed it is probuced. OK, we're talking worst case scenario here but the toxicity issue is one thing. No-one is going to die from breathing it in (not from poison but you can die from smoke inhalation). Visibility is an issue.
Can debate the scientific theory and the possibility of stopping a lithium fire but the practicalities are very different. On board foam type fire extinguishers are a solution but the weight probably defeats the reason for using them anyway. Easily removable panels to allow you to drop a bucket of sand on it defeat the need to contain the batteries etc.
I agree containment is used for car spraying, toxic installations (part of my job and did a lot of work for Wellcome Foundation in their labs so fully conversant with filters and the like) The problem I see is the practicality of doing this in a mobile arena. Big volume to be ventilated quickly = big fan.
Good chargers will deal with a lot of the issues for lipos but they will not deal with all of them. An increased internal resistance of an undersized battery will generate heat which is the main factor in starting the chemical reaction. In feathers the load is very low (I know about the power drawn for spinners but is this comparable to a stalled mag motor?), there is probably a factor by which the battery should be oversized to provide some headroom for the power discharged when a speed controller throws a wobbly and sticks them in full forward and they virtually stall against the arena wall.
Again, I am sure you will tell me that particular elements of that are wrong but the general point is that a fault in a heavy, particularly if the motors were stalled, would draw significantly more power than in a feather. Over sizing batteries is a way to go but by how much?
This raises the issue of what is the correct fuse size for this? Anyone done some research on the amount of current a particular lipo can take and for what duration?
You can make the rules foolproof, but then mother nature will appoint a better fool. Made me smile that did :proud: Absolutely right but that doesn't mean we shouldn't question everything and make it as safe as possible.
Anyways, putting aside all the issues above, if you have a lipo fire and the smoke is contained in the arena and everyone is ok, the time it would take to ventilate the arena would be a commercial issue as it would mean a stoppage of at least an hour (ok a guess but a realistic one) to get back up and ready to go. Is this acceptable even once? Smoke panics people more than fire, it is a much bigger problem in most evacuation situations than flames or heat. It makes people act irrationally and they can injure each other. We talk about containing things in an arena but the smoke will spill out of a net roof and there is probably enough of it to do so from a lipo fire. You cannot guarentee a crowds response, who in the crowd will have a reaction to it etc etc Here's an interesting vid shows people dealing with it http://www.youtube.com/watch?v=yEF456zqdk4 quite good to show the amount of smoke produced and time taken to deal with it.
We used one of nippers packs in little flipper at the uk champs pulling 500A and there wasnt a problem with the lipos, also ls4 pulls over 6000w at 37v spinning up fast and either packs could run a heavy so if we werent allowed them in heavys then the feather rules should also be looked at as they have less armour to protect them. Big nipper has 300A fuses on each lipo pack and 200A on the motors so if a motor stalled it would blow, so the 1000A lipos would never be stressed. No problem.
Perhaps the way round this situation would be to have the FRA and EO's to agree on a particular setup for power using LiPo batteries.
So in practice they would say this power battery from this company. Using one of these chargers, batteries must be encased in a fireproof container of these materials of this thickness, when in the robot. People should be able to show this level of competence when using the equipment.
This would show that everyone in the robot sceen has tried to control and minimise risk.
OK so you have a 1000A lipo and a 300A fuse, all seems very good with a more than adequate safety ratio.Quote:
Originally Posted by graeme
I had a look up to see if I could get some reasonable time/current characteristics on line. Weren't extensive so i settled for these http://www.littelfuse.com/data/en/Data_ ... aSheet.pdf
If you take a look at page 5 you will see the time/current characteristics of this particular 300A fuse.
Follow the 300A line up and you will note that this is quite capable of holding a 450A load for about 1000seconds.
A 1000A load would take 20seconds to blow this fuse
Now I don't know what fuses you are using but I would suggest that the fuses are similar in terms of their actions. To corrctley size a fuse you need to know what the fault current is for a dead short accross the battery therminals and the time you need to clear the fault in.
I would like to see a set of hw lipos set on fire by whatever means over charging or shorting, on a table and physically see what happens.
How much would a pack cost?
Exposed LiPo packs vs large spinning masses, powerful flippers, axes and sharp edges
is something we really want at our events?
It's something we've had at almost every RL and RR event since they started, with the Antweights, I know what we're talking about here is heavyweights but it was AWS9 in Aylesbury that LiPos were first used, we've had punctures and fires since then and we've learnt to deal with them.
Some of the things we've brought in would be difficult to scale up, I'm not sure I could get all the packs I would require to put in Tanto in the largest LiPo, being worst case scenario that all would need dealing with, but we can do other things. There are 2 issues I see with LiPo's:-
1)The way in which they are stored in the robot - they would need to be secured properly and not left to bang around inside the robot where they could be ruptured.
2) Controlling a potential fire - they don't burn like NiCads or NiMH burn how ever it's not like its not controllable, we're lucky that we don't hold that much flammable materials in our robots or in the pits. I would like to point out I know there are flammable materials, but I refer mainly to Formula 1 and a like where LiPo's are used in conjunction with high octane fuel.
If we can cover the main problems I don't see why we can't see them used.
In late ,2010 as part of my masters, I made a set of motors (4) that we're a unique design, in testing them I had 4 packs of LiPos powering the test rig. We did a full load test to prove the high end of the power output, while we ran this test one of the LiPo packs started to swell, upon noticing this I stopped the experiment but it was too late, the pack burst and caught fire in my hands. We didn't have the equipment on hand (although we did have the equipment) to deal with this fire, I had to rush it out and put it in a safe place to let it burn itself out. Cause of the fire was a current limiter failure (wasn't programmed correctly). The pack was one of these (equivalent)
http://www.hobbyking.com/hobbyking/stor ... ouse_.html
At Folkestone 2004, we had a NiCad fire in TX-108 (cheap cells) neither experience was fun, but I've been on the end of fires of our primary power source. The way we deal with them is whats important, we need to develop new avenues of technology or we'll be stuck in the past. Maybe we should look into a specific safety procedure for LiPo before they get totally dismissed.
A 36v 10Ah pack would cost around the £400 mark if you buy the top end sets which are the only batteries I would want to run
Something like these http://www.flightpower.co.uk/index.php? ... cts_id=189
I should also say I'm not interested in running lipos for ragging the arse off them like I do in feathers. Two bosch 750s and a couple of linear actuators will draw bugger all in comparison. My reasoning is purely the fact that you can run a much lower capacity because of the higher energy concentration.
Just an idea but flightpower may be able to give you a discount on a lipo pack if you explain to them that it's for testing to see if they're suitable for robot use as I'm sure they'll do everything they can to sell a load of large lipo packs to robot builders and if they do become the norm as in feathers then that's a lot of £400s for flight power!
I have had problems with lipos in my rc car, in small configurations the cells seem to run down the same amount, but when I'm on 22.2 v 6 cells I am sometimes overdischarging a cell sometimes to under 1 volt, they do swell and don't Wont to charge again. With propably 7 in series minimum we will see more problems even with voltage cut offs set correctly they require serious attention when charging and Inspection after use , any low cells would make the whole pack unusable. I think we should stick to a123s.
Well it's standard practice in featherweights to remove the cells and inspect them before charging and you have to use a balancing charger to keep the cells balanced. Any swelling or damage means that the pack has to be chucked.
I actually disagree. The main technical issues I see are the internal resistance of the battery and correct fuse sizing.Quote:
Originally Posted by terry
The internal resistance of a battery increases over time. It can 'fall of a cliff' and still be within the tolerences of a lipo charger so it should be measured at each event to see if it shows a significant deterioration in resistance. It would be useful for the nipper team to do this during their testing so we have something to compare with.
Fuse sizing can either be done theorhetically using time/current curves or we could simply do some destructive testing and short a few batteries to see when the chemical reaction is initiated. This would also give Jonno his wish to see one go up (Hopefully)
Taking on board everything else which is already done then they are probably as safe as they can be.
Then it comes down to how you deal with an 'explosion' should it happen. OK, it'll be contained anyway, the amount of smoke is an issue as is accessibity and removability of the pack to put it out. As an example it took us about an hour to remove hydras batteries when they caught fire so an easily removable panel and a battery holder which can be cut out with a set of bolt croppers would not go amiss. That said risk assesments for that are Jonno and Alans bag as they'll be the ones dealing with it.
I've been trying not to comment but its so difficult. :lame:
Huntsman went to compete in Robogames with LiPo's. The drive was powered by a 6s 5000mAh 40c pack and the axe was powered by 10s of the same batteries. Huntsman wasn't the only heavy to run LiPo's, but the majority of the big name robots used A123s because they didn't want to spend the money to change when they already had some perfectly good batteries. Mostly it was new build robots with the LiPo's, such as my Huntsman, most of the collage teams and I think Touro Maximus aswell. The Robogames procedure during the safety inspection was just to declare if your robot had LiPo's or not, with no extra checks after they ticked the box. Fires inside and outside the arena were handled the same if it was LiPo or just electronics burning. A clear walk way was kept between the arena and the rear building exit. During a fire it was loudly called out around the pit and the walkway cleared. The dedicated fire marshalls went in when it was safe (usually after it stopped smoking) and covered the robot with a fire blanket and rushed it to the exit and fresh air. The arena also had an extraction fan on the pit side to remove smoke. A fire really only slowed the show down by about 5 minutes but the audianced usually enjoyed it. I checked the skip after the competition and most of the crispy batteries were A123s. The LiPo's seemed to have a better survivabilty rate.
As for resrictions on chargers, fuses, armour and that sort of rubbish they didn't really seem to care. With 650+ robots at the competition it was mostly down to common sense by the builders and firmly putting the boot up anyone who stepped out of line. The restrictions I heard mentioned here wouldn't work if more then 10 robots turned up at a competition. Its more down to the EO knowing and preparing flr what will happen if there is an accident (as opposed to guessing what will happen, big difference) rather then imposing rules on the builders that are too restrictive. Spending 15 minutes to check each robot, pit table and procedures would be too much. And 50 rules on batteries won't be followed. Robogames was a great event because the EO's and arena marshals knew what was going to happen and exactly how hard to kick. I only got kicked a little two or three times, but my collage mates across my pit table got a big kick for their stuff up and shown the door.
And if you want to try being difficult with LiPo's trying taking 7kg of them in a back pack through several international airports. Ahhhhh, fun.
On a side note we just had a promotional day here at a big shopping centre that resulted in the death of 4 or 5 LiPo packs in feather weights. We had one fire in the electronics of one robot (a dead short) but not one bit of smoke from the LiPo's. They got hot, pregnant and fruity but we couldn't get them to pop.
This is exactly the info we are looking for , this is the point of the discussion :-)