Hey guys,
a group of us from school have decided to build a robot
here are my questions
How long do the battles go for? couldnt find it anyware in the rules
are sealed lead acid batteries allowed? rules say no spilling contents but sla's seem the obvious choice and i'm sure i've seen thedm in some robots?
Also in snybody interested in helping get some tv coverage of the event? maybe a highlights package on sbs? sure would make it eaiser to to get sponsorship

Thansks in advance

battles last 3min generally. rumbles can last longer but they dont count for points and are just for fun. a few robots generally run out of power for them.

SLA are allowed,I believe sproing at the recent Ideas Fest was running them at one stage \. power to weight ratio is not as good as many other choices so they are not popular these days.
I think from reading the forum DOSS seam to be one of the better SLA battery's for these applications
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Last edited by seanet1310 on Wed May 13, 2009 8:02 pm; edited 1 time in total

What state are you in?

You might well be better off using the drill batteries that come with the drills, they may last longer.
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Mechanical engineers build weapons, civil engineers build targets

oi new lads, add me on msn if u wanna chat bout all things funky and technical, sir_welchalot@hotmail.com

if your in NSW come to an event and check it out personally
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Andrew Welch, Team Unconventional Robotics

based in vic, were going to try a (temporarially top secret) power train that drws toomuch current for nicads and cant really afford lipos so pb's it is for now, unless were succesfull in our bid for sponsorship ( weve sent a letter around to a few local buisnesses asking for support

If you have to go SLA's, go for the 7ah bricks from Radio Parts (www.radioparts.com.au) - city store. 2.3ah's can be ok for lower powered bots (which it doesnt sound like yours is), but make sure you get fresh ones (check the voltage on the shelf)

Be aware that SLA's are not only heavy, but when discharged fast (as in less than 5-10hours) you get less than their rated capacity from them. In fact, if you discharge them in 3-5 minutes, you will be lucky to get more than 30-40% of their rated capacity. So a 7ah battery will only give out about 2.5ah. Or about the same as 4xA123 M1's which weigh about 1/10 as much.

Good Nicads will sustain around 80-90amps with bursts up to ~120 amps.. which more than most feather sized speed controllers can handle. a good SLA will put out 200-300 amps, but not for very long.

TV Coverage would be great. Got any leads to get it ?
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Where do you guys get your a123S and nicads from, everywhere is real expensive specially for a 24v pack.
As for tv coverage surelly we can just call sombody at sbs and have a chat

Theres a guy in Knox who sells individual cells for around $20 each.
http://airstrike.com.au/

Or you can buy a certain model of DeWalt pack (one of the other guys should know the model #) off ebay for around $150-$200 for 10 cells.

Or, Tim found a Chinese Ebayer who has cells for about $10 each, but we're not sure if they're genuine/unusued cells yet, Look in the A123 forum thread for details on what he found.

Surely it is just a matter of someone giving them a call.. be my guest.

It takes a bit more to organise a TV show than just calling someone.
We have explored several leads in the past and they have come to nothing. If you can find someone at SBS who is interested in producing and airing the show, let us know, and we'll take it from there if you like.
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been having a look around at batteries, is there any reason you guys dont use nimh? seem cheap and high capacity, compared to nicd anyway, do they have high current draw issues?

They're OK. I ran them for a while as weapon batteries

Not as good at pushing Amps at NiCd, and they get hot if you charge them too quick (which we often need to do between matches).

Plus they also seem a bit more fragile than NiCd's. If you abuse them (which we also often do) with overloads, overheats, fast charges, leaving them flat, draining them to the last drop and so on, they seem to lose capacity, and or die altogether (go very high resistance, low capacity) a lot quicker than NiCd's.

They're also quite a bit more expensive - we were paying about $4.20/cell for CP2400 Nicd (in bulk quantities), vs $7.80/cell for 3300 NiMh.. Thats for top quality Sanyo cells

Out of 40 cells, I had about 5 die altogether (less than 500mah capacity from a 3300 battery) over a 2 year period.

Capacity to weight wise they're a bit better than NiCd, but capacity vs cost, and fragility made them about equal, and the lower peak current and charge capabilities put them on the negative (in my opinion - others may disagree)
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woah $4:20 a cell!!! where?

Master Instruments, need to buy 100+ cells to get them at that price though. And for that price, might as well buy A123's.
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https://www.halfdonethings.com/

just buy the A123s off ebay. fake or not i can haul 170 amps out of them for the last 3 events. there good enough.

think 12 of them (2x 21v packs) was about $140 or 150 aud. the new ones are even cheaper?
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are these the one? loom like a good deal
http://cgi.ebay.com/12-A123-3-3V-2300mah-Nano-Phosphate-Hypersonic-Battery_W0QQitemZ370192125865QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item56312b8fa9&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

http://cgi.ebay.com.au/12-X-A123-2300-Li-Ion-Nano-Phosphate-Hypersonic-Battery_W0QQitemZ250409729986QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item250409729986&_trksid=p3286.m63.l1177

or this.

i got mine from the same place as you posted. youll also need an a123 capable charger and balancer (pretty cheap on hobby city ~ $60 max us)
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz