Ant Batteries (Lithium Polymer) BOOM!

**typhoon_driver** · 29th October 2006, 14:40

2) Until further notice, Lithium rechargeable batteries may only be used in robots in the Featherweight class and below.

**mpinner** · 29th October 2006, 14:49

Ahh nuts I missed that.... Oh well Ill have just make a cold fusion reactor.... and then make it fit :P

**grant_ploughbot** · 30th October 2006, 12:14

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!

**maddox** · 30th October 2006, 12:19

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.

**terrorhurtz** · 30th January 2007, 00:58

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 Â£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

**leorcc** · 30th January 2007, 07:48

I totally agree with John and Woody. However i am not going to put A123 cells in my ant.

**craig_anto** · 30th January 2007, 10:46

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.