Are LiPo batteries safe for HW robots?

[tom_kane]

This will be discussed at the next FRA meeting, please comment further!

[grant_ploughbot]

I'll put my view down here so it can ve discussed at the meeting if i'm not there......

I have been using large lipo's in feathers now for about 3 years or more, and in other things for a while too....
Just a couple of facts about lipos -

Lipos DO NOT explode, the catch fire for about 40 or so seconds and then burn out quickly. The Flame is hot, and sometimes quite big if FULLY charged and in good condition, but it doesnt last very long.

In 99% of cases, a lipo wont catch fire. It just puffs up and then needs to be disposed of. Using a puffed battery can then result in fire whilst charging if your very unlucky.

Whilst charging a lipo wont catch fire unless you are charging it wrong, or it is very out of balance. Firstly, to pass a tech chek you need to have the correct charging equiptment (which shouldnt allow you to charge them at the wrong voltages) and balancer. This is the number 1 cause for lipo fires whilst charging, using incorrect chargers.

If a lipo does catch fire whilst charging it should be in a metal box if you work by the FRA rules (i also think charging in the robot should be allowed as long as you can connect a balancer to the pack and visually ceck for any swelling). In the robot is the safest place for batteries!

When in use, the lipo wont catch fire unless its punctured, or the cells are not matched at all (this only happens to the extreme when multiple packs are linked together - i dont think any more than 2 packs should be used in series or parrallel unless all have identical ages and cycles). Over discharging a lipo will get it hot and swell up, permanently damaging the lipo, but it wont catch fire from this. Kenny and I have tried to make a lipo catch fire from an over discharged pack, and its physically not possible.

A Lipo can catch fire if its got a good charge and shorted out for a good period. I wont pass a tech check in a featherweight if a lipo doesnt have a fuse directly inline thats rated less than the peak discharge of the pack. Hopefully that will stop any possible fires from shorts.

If a lipo does catch fire in the arena, then the arena and even organisers should be easily capable of dealing with it - otherwise theres big problems with safety for any fire!
The lipo will most likely have burnt out by the time you enter the arena anyway, but if not then just treat it as normal - its no more dangerous than a normal fire if you have some basic common sense (i.e dont pick up the robot with flames coming out the top!)

In the rules it states that the robot should have a 2mm metal base with lipos anyway, so no problems with setting the floor on fire.

I have crashed alot of helicopters with lipos in the front, and litterally bent them 45 degrees or more. They dont catch fire from it. Alot of people even bend them back and keep using them, although that really shouldnt be done, it proves they are alot safer than people think. Alot safer than pneumatics in the wrong hands!!!

As a tech checker for our events, if i dont believe the roboteer is capable of looking after lipos correctly or dont have any knowledge on how to charge and dispose of them corrctly i wont allow the robot to run for obvious reasons. Also the same with pneumatics, we try not to let people with no experience and understanding of them re-fill bottles or mess around with them without someone experienced checking over them....

[m2xt]

I have a more generic issue with the role in the FRA governing body dictating build rules. The constitition states:

5.5 Governing Body meetings shall rule on all FRA matters including guidelines and regulations for the safe and enjoyable involvement in robot build, operation and events. These meetings shall set the policy for activities of the Association and its representatives.

The recent issue over the 40MHz band and LiPo's are two examples of where decisions have been taken without consulting the membership. I feel the Governing body should address its role in determining the rules, in particular build rules. This could be by being open with its thought process with publishing data that supports its stance, for example a risk assessment that justifies the non-use of LiPo's in Heavies but allows them in Feathers. The FRA Governing body could change its role by making recommendations for or against technologies that are available and legal to use and possibly impose conditions of use (for the Roboteer and / or Event Organiser) following a published risk assessment. The FRA build rules have become too prescriptive and the FRA Governing Body too quick to make decisons that affect the Roboteer directly either through time or money. There is considerable expertise within the community that should be utilised in ensuring that the build rules in particular are reasonable.

The FRA used to have an Electronics Technical representative (Paul Hunt IIRC) but no longer lists one so how can the membership be confident that the FRA Governing Body is voting in changes that have been reasoned and properly presented to allow an informed decision to be made?

[dragonmaster_1]

Copyed from RFL Forum
There are new UN Lithium laws coming possibly as soon as Oct 1st 2009 which will make it more difficult to obtain all Li cells
The new regulations, which are quite readable, are available here:

http://www.nexergy.com/media/pdfs/TRANS_UN_38-3.pdf
Packs are going to need to be tested at a special lab.
These are the tests
Storage at 10% of atmospheric pressure
Rapid thermal cycling between -40 C and 75 C
8g vibrations
150g shocks
Complete discharge through a short circuit while pre-heated to 55 C
Having a 20 pound weight dropped on it from a height of 2 feet
Being over-charged at double the rated current for 24 hours
Being force-discharged (like an unbalanced cell in a pack)

[muchalucha]

I dont know a whole lot about big lipos , as ive only ever used lipos in antweights , but id just like to say , even when a little 400 mah lipo gets punctured , in the one time that it happened to me there was a 1 ft flame , a roar and the thing set the hdpe shell on fire , melted the rubber bands holding it down and shot around the floor a bit , before eventually just smoking and bubbling with heat for a minute or so , i wish i had taken a picture it was incredible ! This put me of using lipos for a long time , so if lipos are made legal , could i suggest that there is a minimum casing thickness for just the lipo , to avoid puncture .

[craig_colliass]

I started this thread having a fundamental misconception about A123 and LiPo batteries I thought wrongly they were basically the same this error was brought to my attention early on in this thread, many thanks for this.
I think it would be interesting for us (who are not particularly interested in the micro-spec of the different battery types) to have a grid of €œIf this happens. This will result.€
For instance if you overcharge, drop, puncture, etc a LiPo, NiCad, SLA or A123 this would be the likely result.
Also the LiPo size in Featherweights, should there be a limit of capacity or voltage? I remember someone saying his LiPo pack would run a heavyweight! If this is true why not let them be run in heavyweights?

Pneumatics
Also off the subject slightly perhaps some safety information and instruction on pneumatics would be a good idea, as a mechanical engineer I found it quite frightening the way pneumatic systems are handled in the robot scene. Many people have been killed by pneumatic systems in the past and they were much less powerful than the ones used in fighting robots, Perhaps some pneumatic circuits that could be advised by the FRA, stating capacity of components and manufacture part numbers etc so there is a minimum standard for components and circuit design. It would be a practical help if we knew this has been tested and approved for a fighting robot. Do the systems have a safety valve that can be tested in the robot at an event?
Hope this helps


Craig

[psycho_fling]

While everyone is on about lipos on here

in my expierence i found them fine just treat them well etc,

saying this i am selling some lipos http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0451474172

as i now do not need them not for any safty reasons

[dragonmaster_1]

More from RFL Forum
Wal-Wart just got fined $350K for not having the proper DOT training....scoff if you like, these rules are coming.

http://prba.org/laws_and_regulations/un ... fault.ashx

[Kenny]

did the talk go through about lipo's in heavys? i'm currently designing a heavy and theres no point building without lipos as the weight saving and the spec's i need to run the parts it will have in it

[dragonmaster_1]

Copyed from Robotmarketplace this is on all there li poly battery packs


At this time, the battery does NOT conform to the UN T1-T8 tests as required in sub-section 38.3 of the UN Manual of Tests and Criteria for lithium-based batteries. Therefore, we are unable to ship by any method until this particular pack has been tested and approved.