LiPo

[chompalot]

Do LiPo's get hot when they discharge heavily?

Although sticking them in a lipo sack sounds like an ideal solution would they overheat?

[Mouldy]

Ok mario I'd suggest a non flammable material... That wording ok for you?

... Putting them in an air tight metal box sounds a good idea, but lipos need breathing space...

[grant_ploughbot]

Sound's like this is a case of things getting out of hand just because they can! At the end of the day we all want to use the best technology and make it easier for everyone to understand and be able to use - There's no point nit-picking as all it's doing is frustrating some people and confusing others!

Anyway, here's the deal with Lipo's for me;

The 2mm metal base rule used to be in the rule's, not sure why it's not now but hey ho. This was a breif statement because there's no point complicating things and making it hard for people to understand. If someone comes with a highly flammable base then it's common sense they should not be allowed to handle a hammer.
The reasons for a metal base for me are as follow's: The metal base helps stop any batteries from burning through thin plastics sometimes used as base plates : It helps with cooling the robot with a fire extinguisher for handling : Also it helps add abit more rigidity and resistance to penetration from flipper's etc that could puncture the lipo's : Burning plastic bases also add extra hazadous fumes to what will already be alot of smoke. We would like to minimise this as much as possible.
It's a basic precaution that's easy to understand and very very easy to implement. A lipo sack would cover most of these points, but it's often fiddly in the robot and doesnt add any resistance to penetration etc.

As Leo said, all that we are aiming for is to reduce the risks and try and cancel out the most common problems that cause Lipo issue's. If there's a simple sensible way to do that then we are all ear's.

Dave hit a point about how competant the user is when he is tech checking. It's a very valid point and again one that we take seriously at Robo Challenge. Over the many years of running events we are aware of what sort of issues are a common trend for certain roboteer's. This varies from being constantly overweight, bad wiring and insulation, history of battery failure's, constant CO2 leaks etc etc. We have spoken to a number of people moving to Lipo's to advise on how to improve their safety level to a standard at which we would be happy for them to attend our event with Lipo's.
Some people may take this the wrong way, but in reality all we are aiming for is common sense, safe useage for a battery technology that is revolutionising the model industry.

With regards to charger's, NEVER charge on a charger that doesnt have a dedicated Lithium Polymer charging setting. You WILL end up with your house on fire! With Lipo's and charger's you tend to get what you pay for - I personally only use the best chargers and the best Lipo's for safety and longevity of the packs.

Lipo's should NOT get excessivly hot when in use. If they are hot, then you are running them outside of their useable spec's and should upgrade your packs. I have a huge experience with these batteries in various uses, and I always spec my batteries to run cold or slightly warm after use.

I think it might be worth me doing some video's to demonstrate safe use of lipo's in robot's and what to look out for - would this be helpfull to you?

Like I said - there's no point making things complicated, just follow the rules, put a metal plate on the base benieth the lipo and enjoy the benifit's of this amasing technology!

[typhoon_driver]

This varies from being constantly overweight

I hardly think that my expanding waistband is an issue at events

[grant_ploughbot]

That's the problem Gary, people don't see it as an issue untill theyre told!

[chompalot]

I was getting round to designing the robot, after being out of the loop for a long time, and could quite easily neglected the metal plate since it's not in the rules.
It's only the discussion which alerted me, to the potential requirement.

[grant_ploughbot]

Like I say, I'm not sure why it's not in the rule's any more. Some event organiser's might not bat an eyelid without one, which isn't a problem. At our full combat event's there is a much larger scope for damage, and that's why we feel it's nessasary to keep that extra little bit of a precaution.

[maddox10]

Ok mario if your going to be such a Little b*tch about it I'd suggest a non flammable material... That wording ok for you?

I'm going to be annoying untill it becomes clear that it's an arbitrary ad hoc personal interpretation.
What is the difference concerning non flamability between 2mm ali and .5mm steel? Or even teflon weave.

If not in the FRA rules, it's to the EO to decline robots or not. And I guess if we're going to look closely, no robot is acceptable.

... Putting them in an air tight metal box sounds a good idea, but lipos need breathing space...

Putting SLA's in an airtight box is asking for H2 buildup. Not a good thing either.

But if we want to build perfectly safe machines, we'll have to include total control on anything. Even grade of bolts.

[Daniel]

Have there been any LiPo fires in robots at european compeitions? I can't remember seeing any on Youtube.

There has only been one LiPo fire here in Australia and it happened to my robot, so I've had a bit of experiance with what can happen. My robot self-righted onto a vertical spinner which ripped two of the cells in a 6s 1800mah pack. There was an extreme amount of heat and smoke, but no fire. There was also little damage from the fire, mostly soot from the smoke. It made a good high speed video but I can't find it right now.
I've also had another battery receive serveral ruptured cells at a recent event and decided to try to cause it to catch fire the next week after I got home, but it proved to be rather difficult to get real fire from the battery. I tried over charging and direct shorting but the only smoke I got was from the wires attached to the battery. I eventualy took a blow torch to the battery to try to induce fire, but I also found the one burning cell didn't ignite the cells next to it and I had to keep applying the blow torch to keep things going.

From my experiance I will not worry about what material the battery compartment is made from in my robots. I will pack my batteries with rubber foam matting to prevent shock damage and cable tie them in tightly. I spec my batteries so the discharge rating is higher then the motors peak current draw and I will try to use controllers with LiPo low voltage sensors. I won't use fuse. And the batteries are kept in the hardest place for spinners to get to.

We could try a Mythbuster alike test. Can a burning LiPo pack ignite a standard arena floor?

When my robot was burning one of the builders decided to rush into the arena and grab the robot and move it to an open area. When he grabbed the robot the 2 burning cells fell out of the robot and remained on the wood floor (lucky for us since he placed the robot in the middle of a public walkway, the bad smoke stayed in the arena). The burning cells melted to the floor, left scorch marks, but did not set it on fire. The cells were still too hot to touch 1.5 hours later and were knocked off with a hammer. The arena was fine.
Also, flame throwers don't burn polycarb

[grant_ploughbot]

Daniel, thank you for the post - Some of that is correct and some not so (flame throwers burning polycarb ).
Like you say, it's actually very difficult to get a Lipo to actually catch fire - it's only usually when the cells are fully charged and have alot of energy in them at the time. Overcharging is the number 1 cause of fires. However, it's not that difficult to get them to let out the magic smoke. As an event organiser we want to keep the smoke levels to a minimum, and the robot cool and safe to handle.
The metal base used to be in the rule's, and like I said I'm not sure why it isn't now. We have been going by those origional rule's and tend to stick by it because it's a simple thing to help towards preventing damage to the lipo and other factor's I've explained.

Mario - I've outlined my reasons why Dave tech check's at our event's in the way he does. Its all about common sense and safety.

I'm going to be annoying untill it becomes clear that it's an arbitrary ad hoc personal interpretation.
What is the difference concerning non flamability between 2mm ali and .5mm steel? Or even teflon weave.

If not in the FRA rules, it's to the EO to decline robots or not. And I guess if we're going to look closely, no robot is acceptable.............

But if we want to build perfectly safe machines, we'll have to include total control on anything. Even grade of bolts.

What's the point in being annoying for the sake of it? it's not helping anyone and just pissing everybody else off! If you don't like the reasons I've outlined as to why we want to see a metal base under lipo's then feel free to post something worthwhile as to how things can be improved rather than being so negative about it all.
We're all here to have fun, it's a hobby!