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Scotch 2216 is the best for the mags because i think it is the closest match to the glue that they use when making the mags. Here is a sort of how to reglue the magnets back in.
http://www.robowars.org/forum/viewtopic.php?t=74&postdays=0&postorder=asc&highli ght=glue+magnets&start=1860http://www.robowars.org/forum/viewto...der=asc&highli ght=glue+magnets&start=1860
http://secure.silmid.com/action_catalogue.asp?sat=2&saa=4&path=~%5BS~%5E1~% 5E~%5E2216~%5EAND~%5E~%5EAND~%5E~%5E~%5D~%5BD~%5E~ %5E4~%5E2216250~%5E0~%5ES~%5Dhttp://secure.silmid.com/action_cata...BS~%5E1~%5E~%5 E2216~%5EAND~%5E~%5EAND~%5E~%5E~%5D~%5BD~%5E~%5E4~ %5E2216250~%5E0~%5ES~%5D
Lol silly me of course that question should have gone in the ask woody thread :)
Thanks a lot. Sorry to have hijacked this thread.
:rofl:
Any news yet about the lithium-cells? When will the decision be taken, if there allowed or not?
yea still waiting here on a desision, come on FRA get ur finger out
I second the motion to the pulling of said finger. :)
Seriously, any news on when it will be on the agenda at least?
Notes from the last http://www.fightingrobots.co.uk/meet...07.pdfminutes:
So ....The time scale for said trials are likely to be?
Note:- John is updating the A123 build and test page regularly.
http://www.terrorhurtz.com/a123/http://www.terrorhurtz.com/a123/
And i read that page religously. :)
Well we ran them for the first time at a competition at Guildford. They performed very well, with no problems. They were barely warm after the fights. However, we only had about three fight, and two of those were against a slot machine...
We will be running them again at Exeter, so that should be a better test.
John
Again, no problems at Exeter. Worked well.
The only question now is how to balance them easily and well. I suspect that some of the commercial balancers out there dont do a particularly good job of it.
At the moment I am balancing them manually, with varying degrees of success, using a 16 channel analogue-to digital card in a PC to view the cell voltages.
John
i thought that one of the main pluses about these cells was that they balanced themselves in a similar way to nicads?
No, this is one of the differences between these and NiCads - like LiPos, they need to be balanced.
If building packs, then balancing wires need to be built in.
If a cell in a pack is repeatedly over-charged then it will be damaged. There may be some small self-balancing effect (the over-charged cells will get rid of the excess energy as heat). This should not be relied upon.
Another difference from NiCads is that M1 Lithiums do not like getting hot. Damage will start to occur if the cells get over 60 deg C. Fortunately them seem to stay cooler than NiCads under discharge.
The standard DeWalt drill packs have connections to the end of each cell built in and the DeWalt charger balances the cells at the end of each charge (if it deems that they are out of balance).
(Message edited by terrorhurtz on July 14, 2007)
(Message edited by terrorhurtz on July 14, 2007)
From what Ive read from the about the M1 cells they only need balancing every 10 or so cycles. No sure how this pans out in the real world though.
Ive been looking at balancers that can be slaved together via a data link to work with upto a 12 cell pack. Ive no idea how good they are but from memory the data sheets say they balance within 0.01v... may have been 0.05v though? I Might be a bit off though cos all my info is at the office.
What is the imbalance tolernace like on the M1 cells?
I am still experimenting with ways to balance these cells, but already its clear that they can only be effectively balanced right at the end of charge, or maybe even after the first cell has peaked.
See http://www.terrorhurtz.com/a123/images/DeWaltBalance2.pnghttp://www.terrorhurtz.com/a123/imag...ltBalance2.png
If this pack had been balanced at half-charge, it may have seemed that the pale blue cell was high. But in the last few minutes of charge, it turns out that it is low.
This graph is of the DeWalt charger doing its thing. Notice that all the balancing is done after the first cell has peaked. The first cell is used as a reference to which the others are then matched, which is rather more sophisticated than the other balancers that I have seen. The balancing is done at around 0.15 Amps.
Regarding voltage difference between cells - at peak I would say 0.05V is sufficient. But just before peak, the voltage of the cells is changing rapidly, so achieving less that 0.05V difference at that point is not straightforward.
This graph is a rather extreme example - they would not normally be that far out.
(Message edited by terrorhurtz on July 15, 2007)
John,
I know very little about electrickery ... but ... and this may well be a daft idea ...would it be posible to use a diode ,zener and resistor combo across each cell to attain balance?
Hi Woody,
It seems that none of the easy/obvious balancing schemes work, or at least not well.
e.g. effectively getting the high cells to charge the low ones - the lower ones need to be charged to a higher voltage initially and then they drop back.
or charging all the cells individually to the same voltage doesnt seem to work either - they seem to remember that they didnt get there in the same time, even after resting for an hour.
Looking for a balancer solution
This is interesting:
quote:
. High temperature performance
It is detrimental to have a LiCoO2 battery working at elevated temperature, such as 60C.. However, a LiFePO4 battery runs better at elevated temperature, offering 10% more capacity, due to higher lithium ionic conductivity.
Source: http://mysite.verizon.net/adaptron/batteries/Lithium/Iron/Phosphate/index.htmhttp://mysite.verizon.net/adaptron/b...hate/index.htm
Point number 4 is interesting too.
A123s website is not very informative either but I guess the ones in the dewalts are the ANR26650 cells. The only thing I can find on how to charge them says you need to charge using a Constant current, then constant voltage upto 3.6 Volts per cell starting at 3 Amps, but can be fast charged at 10 Amps. Interesting to note they also said that the low voltage cuttoff is 2V per cell at 25 degrees C and 0.5V below freezing, but this is not what the dewalt chargers do after looking at Johns graphs.
I was just wondering if you charged them like this if you would still get the 1000 cycles life they claim. If so I think it could be done relativly easy but you would really need one charger per cell, maybe a balancer could be used and one charger per pack but we wont really know until someone tries it a 1000 times without any problems.
Some info here:-
http://www.fmadirect.com/support_docs/item_1229.pdfhttp://www.fmadirect.com/support_docs/item_1229.pdf
Hi John
Been trying to get in touch dont know if you got my emails. If not could you email me reference what we talked about at the EU champs
Regards Tony.
Sent an email Tony.
Yes, the ones in the DeWalts are the ANR26650 cells (26mm diameter, 65mm long). These are the only cells that A123 currently produce. The larger cells (M1 HD and M1 Ultra) are not in production yet.
The A123 cells do seem to perform slightly better when warm, but apparently they still suffer a reduction in life if they go over 60 deg C.
The main reason to balance the cells is so that we can use simple chargers at competitions - so we dont have to fiddle around connecting all the balance wires every time they need to be charged. Also cheaper.
Commercial chargers are now availiable but the associated multicell balancing is not
http://www.astroflight.com/store/store-type-tem.html?item=products:af-106-123&sid=0001jLBTKVBTuxwtQ82c916http://www.astroflight.com/store/sto...:af-106-123&si d=0001jLBTKVBTuxwtQ82c916
This German manufacturer can supply A123 gear ... at a price ...the charger is expensive but it has a great range.
http://www.first-products.de/pulsarbeschbgengl.htmhttp://www.first-products.de/pulsarbeschbgengl.htm
Cheap six cell balancer .... can these be Daisy chained?
http://www.astroflight.com/store/store-type-tem.html?item=products:af-106-123&sid=0001jLBTKVBTuxwtQ82c916http://www.astroflight.com/store/sto...VBTuxwtQ82c916
(Message edited by woody on August 09, 2007)
Schulze in Germany has also confirmed that next to its line of chameleon chargers their LipoProfiBal8 and 14 is also suited for balancing A123 systems cells.
Woody - I think what Andy meant is that there is no 10 cell balancer currently available. It is anticipated that most heavyweight robots will use 10 cell packs. The Astroflight only does up to 6 cells.
Schulzes biggest one up to 14 (see other topic).
Can we keep the techincal discussion on Li-technology for another topic?
The problem I have at the moment is that I work with lithium batteries on a professional level, and therefore have a good understanding of the possibilities and risk involved. Yet even though the A123 cells seem safe enough (not more dangerous than NiMh) and I am perfectly capable of handeling the cell balancing problems, Im not allowed to use this technology.
This is frustrating, especially since I have to wait until other teams have demonstrated its safety, and effectively have quite a sizable advantage over the rest. This is assuming they are not obliged to couteract the weight advantage.
Why not provisionally allow the use of A123 cells, with an obligatory through techcheck to make sure it is used correctly?
Stefan,
While you may be quite capable of handling A123 cells safely there will be be quite a few teams that cannot as yet.
Could you mail useing info@fightingrobots.co.uk with what info you have please. It would then be put around the test group.
On A123 subjects can we transfer to the thread on safety discussions please?
Above 5 posts moved here from General Chatter.
Stefan - I have been ringing round all sorts of companies (ripmax, Thunder power, kokam etc) and not one of them can give me a straight answer to my question. Do you know how dangerous the fumes of a lithium (and other batteries, i know NiCads are very bad) in a fully closed arena are? Our featherweight arena is fully enclosed, and the smell of a burnt out motor lingers in the air for a while and we are concerned about the effects of a burning battery. Venting the arena wouldnt be a problem to do, but I would breathing apperatus be needed or is it very low risk?
If anyone knows the answers could you please let us know asap - Safety is our largest concern and with a fully enclosed arena things like too much C02 or other chemicals in the air could be hazardous.
On my desk I have some info on a Lithium-Cobalt-Nickel-Oxide cell, which is the kind that burns violently. Unfortunetly I cant tell you which cells these are, but they are NOT A123 cells.
It states:
Suitable extinguishing media: Dry powder. Metal fire-ex extinguisher typ PM12i, Metal fire-ex powder typ PL-9/78 DIN/EN 3SP-44/95 Carbon dioxide
Extinguising media that must not be used: Extinguisher type D, Water spray jet.
Special exposure hazzards: Risk of formation of toxic pyrolysis products. In the event of fire the following can be released: Hidrogen fluoride (HF).
Special protective equipment for firefighters: Use self-contained breathing aparatus. Wear full protective suit.
Additional informatio: Cool containers at risk with water spray jet. Fire residues and contaminated firefighting water must be disposed in accordance with local regulations.
Even though the warning, I know the company use water for extinguishing them.
I also have a list of chemicals used in the cell. Mail me if you want it, Im not going to disclose this on an open forum :) I will have to ask if such information is also available for A123.
Here are some MSDS (Material Safety Data Sheets) for various battery brands and materials:
http://www.batteriesplus.com/t-msds.aspxhttp://www.batteriesplus.com/t-msds.aspx
I dont know the situation on this, but will the robots testing the A123 cells be using them at this event?
I hope not as it is a big disadvantage to the other teams in the competition as large weight loss can be gained with these batteries and higher performance (24v bosches ran on 30V). It might be a little late to mention it as I expect the teams using these batteries have probably bumped up the weight to 102kg now but i know If i was in the competition I would certainly not be happy with it!
Hopefully I havnt noticed it anywhere that they are already banned from the UK Champs:)
I have wondered this myself, but then I came to the conclusion that for a true test of the A123 cells, the UK champs is the place to do it. I dont mind if the robots are altered because of the weight difference, even though I doubt it that something has been done to the robots in question.
Grant, I would assume not.
There were 2 teams accepted by the FRA onto the trials of these
http://www.fightingrobots.co.uk/meetings/014_03_02_07.pdfhttp://www.fightingrobots.co.uk/meet...4_03_02_07.pdf
Those two teams were Mute and THz. Mute are not running in the competition so theyre not an issue, and I doubt that John would want to be seen as having any unfair advantage over others (other than the obvious engineering skill) so I wouldnt expect John to run trial technology in the FRAs UK competition - but John would have to answer that one for himself......?
... quick edit - could always just do a little bit of weight maths to ensure that those robots that are running the cells come in at the Nicad weight so trial teams dont have to fiddle ? Just a thought....
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
(Message edited by storm on August 13, 2007)
Yes, we are planning to run A123 packs in THz at the champs. These cells need to be tested in a realistic environment and as Leo says, the UK champs is the best test for them. Assuming that we get through a few rounds...
If we have no problems at the champs, then hopefully they will be aproved for use by everyone shortly after.
Althought there are now two other teams approved for the trials (Kan-Opener and Das-Gepak), we may be the only team running them.
I will be adding some ballast to reduce the weight advantage.
John
John ...I think the concern was that the Robot weigh less than the max weight .......thus showing that no unfair advantage has been acquired by the addition / upgrade of other items afforded by this weight gain.
Youve gained 2kgs ish .....therefore your bot should weigh in at least 2kgs UNDER the max weight allowance..... thus satisfying certain parties that you ( and any other test bots ) havent gained an unfair advantage by adding in bigger and heavier valving or something similar.
(Message edited by woody on August 13, 2007)
quote:
I will be adding some ballast to reduce the weight advantage
Right on the tip of the axe. :rofl:
I think it is a good thing to see how they hold up in a full-on enviroment. I say go for it.