can you use normal chargers from NiHm on LiPo battery's or do you need a special charger
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can you use normal chargers from NiHm on LiPo battery's or do you need a special charger
Some can do both, but are primarily LiPo. What charger do you have?
just the bog standard rc 1s
Wouldn't really say there is such a thing, most LiPo chargers I've seen though advertise it with lots of large writing on them so I would assume yours is not one of them. They would also have a balance connection.
probably easier and cheaper to stick with NiMH battery's and chargers then
for lithium polymer, no you can't however there is a way for the lithium A123 cells using a dapter. A bit of kit that sits in between the charger and cells and cuts off at the right voltage.
Most modern day chargers that can do enough Nimh / Nicad cells can do Li-Po and have a built in balancer.
I got an iMaxB6 for £8 On ebay. Here's one for 99p..... Whether you trust it is at your own discretion.
http://www.ebay.co.uk/itm/IMax-B6-Digit ... 3f1033d919
ok will look into it a bit more thanks
I know this is mostly resolved, but the build rules state chargers must be built for the same chemistry of battery. So you can't use NiCad on LiPo, for example.
I have been reading the rules with regards to LiPo batteries and there is one thing that I have been told a few times but doesn't appear to be in the rulebook; Metal boxes for lipos.
I have been told that Lipos have to be charged in a metal box and/or a Lipo sack, and should also be in a metal box inside the robot, or have at least a 2mm thick metal base underneath to protect the floor if the lipos go up.
Can someone clarify this ?
Thats right Dave...
the metal box for charging is redundant, those rules were drafted up before lipo sacks were easy to get hold of... get a lipo sack. There cheap enough on Ebay these days.
At tech check for people using lipos i check for the following;
2mm+ METAL base plate under the lipo + security of the lipo (I.E. It isnt cable tied to the pneumatic cylinder *cough* Mr Lear *cough*)
Secure well insulated connections within the robot + the connectors being used are sufficient to cope with the maximum current draw.
Sufficiently rated fuse on the positive side of the lipo, thats rated below the maximum discharge of the lipo.
The visual state of there lipo
The charger + balancer combo the competitor is using is suitable
The competence of the person using the equipment.
Im a bit more strict then some tech checkers when it comes to lipo's, but most of the people using them so far have enough common sense to think of all that them self.
I see that the type of metal hasn't been specified, is aluminium OK for the under LiPo plate?
Don't see any remarks on metal battery-baseplates.Quote:
7.8 LiPo
Lithium Polymer batteries have specific limitations and extra precautions which must be adhered to.
7.8.1 Balancers
Appropriate balancers must be provided if not part of the charger. They will be inspected during the
Technical Check. LiPo batteries should be properly balanced to prevent damage occurring to the cells.
7.8.2 Voltage Cut-out (Advisory)
The robot should be fitted with an under voltage cut-out or alarm set at or higher than the battery
manufacturer€Ÿs recommendation to prevent the batteries from becoming damaged by over discharge.
7.8.3 Fusing
A fuse rated below the maximum burst discharge of the battery must be fitted.
7.8.4 Extra Equipment
Roboteers using LiPo batteries must provide a LiPo sack.
7.8.5 Inspection
LiPo batteries must be removed from the robot, inspected and placed into a LiPo sack prior to and during
the charging process.
7.8.6 Charging
Lithium 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.
7.8.7 Damage
LiPo batteries showing any evidence of damage or swelling must immediately be placed a LiPo sack and
removed to a safe, well-ventilated area such as outdoors.
How set in stone is the metal plate rule?
Well according to the rules it's not there at all. However with Mr Moulds experience with lipo's, the metal plate and/or box is well advised.
Oh well, I have a piece of foamed magnesium that will fit fine below the 5S 5000mAh 30C Turnegy pack.
Also, using a fitting LiPo bag in the robot, isn't that a better solution? It's light, and made to contain LiPo problems.
Would a 1/2mm (I am not sure of the thickness) sheet of Titanium be sufficient to protect the rest of the robot? I think I have just enough space to get a box around each pack (I am using two packs to get different voltages). What about other fireproof/heat proof materials like ceramics, will they comply with the unofficial 2mm plate rule?
I'm thinking about combining 2 capacities in the unofficial 2mm guideline. Foam for shockprotection, and metal because its asked for.
I'm wondering if I can compress steel wool into foamy metal sheets.
ive now had to bond some 5mm aluminium plates to the 5mm polycarb armour above and below the lipo but the plates have small gaps in to allow wires to pass through. thats the best i can do!
I wouldn't want to put steel wool near a lipo even if it is compressed. Worst case and your lipo does go up then it doesn't take much for steel wool to go up.
Gents to be fair, your machine should have a 2mm plate underneath to protect the other parts of your machines.
Just get a small plate of ti off ebay and job's done.
I had planned for a full metal box for both my feathers anyway just for security and ease of removal.
Dave mentioned above the connectors should handle the max discharge of the lipo. In my case, thats 150A. Its a given than conventional Andersons will not handle that, since they were already melting the housing with the NiMH's in there :P. Deans are, from what I understand, also insufficient, but EC5 connectors may suit purpose.
Can I get some insight from lipo users what they use ? My concern is mounting a new link in Satanix is going to be problematic and it uses Andersons.
ec5 connectors = :mrgreen:
Mario- that magnesium comment was funny... Well done?... :|
Dave- deans will be more then fine for satanix... I've tested deans to be reliable at 180amps... They start to weld together at 200a... You won't be pulling that much.
The 2mm metal base rule was agreed to prevent lipo fires causing an arena with a wooden floor to ignite (should a lipo fire happen in the arena) ... So moan all you like, but if you set fire to an arena I doubt you'd be very popular. This rule could do with clarification by Kane... But it's something I'd advise.
who builds a robot with a less than 2mm base anyway?
Not many, but people can build robots with a thick PLASTIC base that could be melted away in the event of a lipo fire.
I was thinking of using kevlar / carbon fibre
Can we avoid the metal base requirement if we have our lipos in lipo bags in the robot?
I would think that it would satisfy the requirement, but since it seems to be an event organiser requirement then we would need to seek the advice of the event organiser.
Also it needs to be specified in the rules so that we can design robots which can compete if built to the rules.
Who do we approach?
It does what you asked for, being 2mm thick metal. Also, compressed steelwool meets that criteria. Both are utterly daft idea's, as both types burn easely enough with the right kind of stimulation. If I want to pull it to utterly idiotic level, what about 2mm pure sodium. Also metal...Quote:
Originally Posted by mr_turbulence
And to prevent a LiPo fire burning down an arena, a 0.3 mm thin fully enclosed steel box will do a better job than a 2mm thick ali plate under the LiPo. As if orientation is unchangable in a robot.
And of course. We could try a Mythbuster alike test. Can a burning LiPo pack ignite a standard arena floor?
BTW, ali can burn quite nicely if the circumstances are right. HMS Sheffield as point in case.
It's not a rule, as it isn't in the build rules. It's an guideline, yours.Quote:
This rule could do with clarification by Kane... But it's something I'd advise.
I remember talking with Grant about this in the past, basically if the lipos are contained in something to prevent fire from spreading to the arena floor, and having a fuse in place to catch massive power draws, lipos are perfectly fine to use. Something like a non-flammable metal or fiber weave like lipo sacks have comes to mind.
Do LiPo's get hot when they discharge heavily?
Although sticking them in a lipo sack sounds like an ideal solution would they overheat?
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...
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!
I hardly think that my expanding waistband is an issue at events :lol:Quote:
This varies from being constantly overweight
That's the problem Gary, people don't see it as an issue untill theyre told! :proud:
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.
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.
I'm going to be annoying untill it becomes clear that it's an arbitrary ad hoc personal interpretation.Quote:
Originally Posted by mr_turbulence
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 SLA's in an airtight box is asking for H2 buildup. Not a good thing either.Quote:
... Putting them in an air tight metal box sounds a good idea, but lipos need breathing space...
But if we want to build perfectly safe machines, we'll have to include total control on anything. Even grade of bolts.
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.
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.Quote:
Originally Posted by maddox10
Also, flame throwers don't burn polycarb
Daniel, thank you for the post - Some of that is correct and some not so (flame throwers burning polycarb :proud: ).
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.
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.Quote:
Originally Posted by maddox10
We're all here to have fun, it's a hobby!