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Hi Guys,
I found this vid and thought you might like to see it. I had no idea Lithium polymer batteries were this dangerous.... It made me think of taking mine out of my Ant.
http://www.youtube.com/watch?v=z3o_2mwRPdwhttp://www.youtube.com/watch?v=z3o_2mwRPdw
http://www.youtube.com/watch?v=0MiM2E6pvfghttp://www.youtube.com/watch?v=0MiM2E6pvfg
i just realized.
we shouwed this footage to the FRA commitee at the last meeting. the new lipo rules are what resulted.
This effectivly makes a lot of current ants potentially illegal under FRA rules. Does the FRA have any recommendation here? do current ants need to follow the new rules, or are their batteries small enough that we can say this weight class is exempt?
It just goes to show that sites where you can buy LiPos from come with warnings for a good reason.
--
Mike
http://www.bobblebot.co.ukhttp://www.bobblebot.co.uk
http://www.antweights.co.ukhttp://www.antweights.co.uk
The problem is if I go for any other battery it will be too heavy or won€™t have enough juice to last a fight. I could be wrong but I don€™t think you can beat the power to weight ratio of these things.
I understand that the makers of the Tesla car (http://www.teslamotors.comwww.teslamotors.com) are using similar batteries, they had to amour plate the battery box to protect the car if one should blow.
Im just wondering if Lipos could be legal in heavier weight classes so long as the battery area is sufficiently armored.
Extract from .....
http://www.fightingrobots.co.uk/meetings/013_30_09_06.pdfhttp://www.fightingrobots.co.uk/meet...3_30_09_06.pdf
6. The use of lithium based rechargeable batteries
It was made clear that the use of lithium batteries posed safety problems for use in robots.
It was proposed that a temporary set of rules would be incorporated into the robot build rules and must be strictly adhered to until such time that our members have experience of handling these batteries and event organisers are happy with any safety implications.
6.1.1
Lithium rechargeable batteries will be permitted subject to the following restrictions:-
1) The event organiser must be informed prior to the event and approve their use.
2) Until further notice, Lithium rechargeable batteries may only be used in robots in the Featherweight class and below.
3) Only chargers specifically designed for use with Lithium rechargeable batteries may be used.
4) The robot must be fitted with both an under voltage cut-out set at or higher than the battery manufacturers recommendation that will prevent the batteries from becoming damaged due to over discharge.
5) Batteries must be removed from the robot, inspected and placed into a sealable steel or other suitable heat proof container prior to, and during the charging process. (It is the responsibility of the roboteer to provide this container, which shall be inspected as part of the normal €˜tech check€™.)
6) Batteries must not be left unattended at any time during the charging process. (Leaving batteries unattended while charging will be considered a serious breach of pit safety and may result in you and your robot being removed from the event.)
7) Batteries showing any evidence of damage or €˜swelling€™ must immediately be placed in the heat proof container, covered in salt, the container sealed and removed to a safe area outdoors.
8) A suitable quantity of salt, sufficient to completely cover the batteries in the event of damage or fire must be available. (If not provided by the event organiser, it will be the responsibility of the roboteer to provide this.)
Perhaps these will suit the needs of feathers better?........sorry no Ant stuff:sad:
http://www.a123racing.com/http://www.a123racing.com/
Related link for obtaining similar batteries from the new Dewalt battery packs.
http://www.rcgroups.com/forums/showthread.php?t=587606http://www.rcgroups.com/forums/showthread.php?t=587606
Lithium Ions.... Are they safer than Lithium Polymer batteries? I.e. Do they explode?
You could have chased around the site yourself!
http://www.a123systems.com/html/tech/safety.htmlhttp://www.a123systems.com/html/tech/safety.html
The answer appears to be.... NO
They quote 3000 watts per kg!!
http://www.a123systems.com/html/tech/power.htmlhttp://www.a123systems.com/html/tech/power.html
(Message edited by woody on October 29, 2006)
Wow!! A123 batteries are perfect for our application. Im very impressed.
I will buy some for my Middleweight robot at some point. Doesnt help for the ants tho :o(
2) Until further notice, Lithium rechargeable batteries may only be used in robots in the Featherweight class and below.
Ahh nuts I missed that.... Oh well Ill have just make a cold fusion reactor.... and then make it fit :P
James, just in response to your post. I dont think any weight class can be exempted. Even if they are small, the potential for damage and injury is still quite high.
The main points I would ask Ant builders to note is 5 and 6.
Do not leave your batteries unattended and have a suitable container to put them in.
I use lithium polymers in my featherweight - and to apply with the FRA rules the low-voltage guard only weighed in at 7grams. 7grams and a little bit of care cant be too much to ask in an ant!
Removing the batteries from an ant could prove difficult. I know its not possible in Malankia Baba Yaga.
But it is rather easy to put ant and all in the heat proof container.
Wouldnt that be the same result. With the disadvantage, if the batteries explode/burn that the ant is destroyed.
I agree with mario on this, id rather just chuck the entire ant in the salt and deal with the damage later then trying to pry out the battery.
I think we need to be clear on the different Lithium battery technologies available.
1) Conventional Lithium ion. Liquid electrolyte. Hard case.
2) Lithium ion polymer/Lithium polymer/LiPo - as used in RC electric aircraft. Electrolyte is held in a solid polymer. Soft case.
3) A123 M1 Lithium ion cells - cylindrical metal cells as used in DeWalt 36V cordless tools.
http://www.a123systems.com/http://www.a123systems.com/
http://www.a123racing.com/http://www.a123racing.com/
The A123 cells use a significantly different technology from the other types of Lithium Ion. They do not suffer from thermal runaway when over-charged and they are enclosed in a metal can, providing physical protection.
I think the temporary rules covering Lithium ion use are sensible, however I dont believe that such precautions are required for the A123 Lithium Cells.
As Woody pointed out, see:
http://www.a123systems.com/html/tech/safety.htmlhttp://www.a123systems.com/html/tech/safety.html
Clearly tests need to be carried out, but hopefully these A123 cells can provide roboteers with the performance we are looking for, but without a lot of the drawbacks of LiPos (risk of fire, short life, easily damaged.)
Note that these sort of cells may not be for everyone - they are NOT as easy to use as NiCads. They require special chargers (actually simpler - just a voltage cut-off) and they need to be balanced occasionally to ensure that no individual cell can be over-discharged. And they are not currently available made up in packs suitable for robots.
LiPos will be damaged irreparably if ever discharged below 2.5V per cell. The A123 cells are more tolerant of this (you may get away with it once or twice), but it still needs to be avoided. So you have to ensure that your bot has surplus battery capacity and you need to charge before every use.
Prices for the A123 cells are currently comparable to good NiCads - around £80 for a 36V 2.2Ah DeWalt pack (10 cells). e.g.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=160078463440http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=160078463440
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=330082381190http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=330082381190
We shall see...
John Reid
http://www.teamhurtz.comhttp://www.teamhurtz.com
I totally agree with John and Woody. However i am not going to put A123 cells in my ant. :)
Antweights do not folow the FRA rules as was desided back when i was Antweight Rep, Antweights follow there own guidelines which the FRA adopted to follow as well, these rules include the flea weights to superants.
The FRA cannot simply tell the ants what to do the ants are self gouvnerning, the fact that the FRA doesnt have a single ant event jus goes to prove the point that the Ants are doing jus fine on there own, and have done since before the FRA was formed.
Interesting comment Craig... But there is nothing in the rules specifically to stop you fitting an Antweight with a Lithium battery anyway.
Not to mention the FRA dont do featherweight or heavyweight events either :)
I think the point Craig was making was that the Antweight World Series has been running with LiPos since they first became popular (ie affordable) as has the Reading Robot Club. For the AWS we now have virtually all of the field running LiPos and have not had any issues occur. All of the competitors know the issues - any new people are told - and the cells are treated with respect...proper chargers, avoidance of puncture and reasonable handling.
They are really only a hazard if not handled correctly....Id argue the same about virtually every aspect of combative robot building in all weight classes....rules for the use of welders anyone?