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At some point im going to have to replace my hawkers, i am thinking about ni cads, but was wondering what the differance between ni-cad and ni-mh is. As in would it be possible to use 2500ma ni-mh cells in place of the 3000ma ni-cad cells which most people are using? i dont really have the money to just try it, so im wondering if over people have, and what advantages there might be. Ive also seem ni-mhs for around £2.50 per cell, and cost is an issue.
I dont know which cells you are refering to but in general Ni-MH cells dont have nearly the same current draw capacity of say bot-packs. So not normally an option for heavyweights.
Ed - Team Turbine
Im a bit wirey of useing Nicads now, ive heard they will be made illegal next year and i wouldnt want to buy more battries in a few months time.
James I dont know where you heard that but it doesnt sound good if it proves true. Will that be the same for Ni-MH as well? Will that mean we are back to using lead acids again?
I am lead to belive that Ni-MH are more enviromently friendly. Would this not mean that more people should look in to the use of these batterys if Ni-CADs are likely to become unavailable?
Im a bit wirey of useing Nicads now, ive heard they will be made illegal next year
.... if thats true Black and Decker and the rest of the cordless market are going to be pissed, were only 12 weeks away from next year !
Luckily its not - The EU currently has a directive which plans to ban phase out the use and sale of NiCad cells in 2008 with a complete ban in 2010. I wouldnt panic just yet about NiCads becoming obselete - and anyway this doesnt allow for the fact that you could still buy them from the US if you wanted to after they are phased out in the EU.
Mark : in answer to your question, I do not believe that there are any NiMH cells at the moment which can rival the Sanyo N3000CR NiCad cell which people are using to run robots with - it can deliver peaks of almost 200amps and can easily put out 100amps for 10 seconds at a time.
You could get around the problem by putting additional NiMH packs in parallel, however that would involve buying more cells that you need to give you your capacity, weighing (and costing more) - and thus defeating the point !
Your best bet would be to look for someone selling some NiCad packs off... have a look in the Archive area of the For Sale section on the forum for people who have been advertising them for sale - its possible they didnt sell them before their advert was taken down !
Hope thats of some use... and some reassurance to anyone who could have thought NiCads had 12 weeks left on the shelves !
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
Note that generally speaking when choosing how many NiCads to use, your choice is based on current delivery ability, NOT capacity. We generally only use 1 to 1.5 Ah out of each pack in a fight (running Boschs off three 24V packs).
If just running drive motors for a heavyweight, then three packs is about right. If also running an electric weapon that draws a lot of power, then you would probably go for four packs or more.
You should plan to NEVER run your nicads flat. Once you feel them slowing down, you should immediately stop. Continuing to draw heavy current from them risks reverse charging one or more cells in the pack, which will over time damage them.
I wouldnt consider using any cell other than the Sanyo N-3000CR. It is what the vast majority of people use.
I agree with John and Ed there is alot of scare mungering going around about batteries but certinly by the year 2008 i dont think this set of ni-cds will be up to much.
I personally would only use the Sanyo N-3000CR or the Sanyo CP-3600. These cells can deliver 80 and 100amps continious respectively.
Regards
Ian
oppps. i was told it would be next year they would be made ilegal.
Cadmium itself is the issue, so depending on its application depends on the timescale. Ed seems to know what hes on about there so thats good enough for me.
You might want to speak to the stinger team, or the draven team. As far as I am aware, they both use F call NimH, and the big nipper team use C (or is it sub c) NiMH (bet Im wrong and they are NiCad now!!)
Last time I looked in stinger it had SLAs.
Ive heard some NiCads are rechargeable, but I could be wrong. Theyre definitely more powerful than NiMh batteries, and I think as powerful as SLA batteries, depending on the robot. :wink:
Team Gore
Kody, NiCads have always been and always will be rechargeable. I dont think anyone would be using NiCads or NiMHs if they were use once and throw away job.
NiCads are lighter then SLAs, but the SLAs can source a lot more current on peak then a NiCad and they can also take more physical abuse. The Nicads have a much better effeciency rate then SLAs and also are much lighter.
I belive Behemoth also uses Saft Ni-MH cells.
james,
We use 2400mAh Sanyo C cells and yes they are NiCads. NiMH just couldnt provide the current.
Weve simply got 3x 9.6V & 1x 7.2V RC Racing packs to make up 36V with 3 of these in parrallel (Yes weve changed it again). We did not take theses packs apart all we did is cut the connectors off and joined them together. Each cell is spot welded to each other at 5 points unlike standard packs with just one weld. They are designed for model cars to be fully discharged in 5 minutes.
We have however burnt the plastic of a few cells when just running one set on the weapon and stalling the motor for a while (with 120A current limit) so you do need to be careful if using these size cells. A test we did a few weeks ago showed a 2V drop with 84A with one 36V pack (better than most Lead acid).
The 2400mAH cells are far better that the 3000mAH for weight/capacity but have a far lower current rating. We simply used them to get the robot down to weight from Lead Acid as the 3000mAH ones would not provide much weight saving. From memory our cyclon Lead Acid battery weight was 9kg, the 2400mAh (at 28.8V) was 4.5kg and the 3000mAh was 8kg.
If you can use the 3000mAH ones then those are the ones Id recommend.
Err.. Meant sub C Cells :)
I have approached many manufacturers for their recommendation for Ni-Cad or Ni-MH cells in heavyweights and not one had a product in their range that would suit (including Sanyo). However, there is considerable experience of using the Sanyo N-3000CR both in the US and the UK in heavyweights and that experience is worth far more that any spec sheet. Technobots alone has sold over 4,000 N-3000CR cells (either singularly or assembled into packs) to European robot builders over the last 2 years and failures have been rare. The failures I know of have been more often than not been due to incorrect usage. As far as I am concerned, there is no real choice, its the Sanyo N-3000CR but I keep looking.
Paul
And what about Bosch motors? Im considering them, but I dont think theyre as powerful as some MagMotors
Team Gore
we use saft ni-mh cells in typhoon 1 + 2, they do what we need them to do and havent given us any trouble
It just depends on the needs of your machine
Too true Gary. Hell you won RW7 with them! :)
Team Gore
Kody, the ruggedized Bosches, like Technobots sells them are just the best power/weight to pricetag ratio.
Thats the main reason so many people use them.
To go for a stronger motor ,like the Mag will increase the total pricetag enormously.As you need stronger speedos, and more batterypower.
In other words, it all depends on budget.
At the moment I still use SLA batteries, and not even the most expensive ones either, because I do not need to buy the more expensive NiCD batteries and matched chargers for them.
Ok thanks. :)
Im starting to putup some blue prints of Wedginator, but I need to install AutoCAD first.
Team Gore
pah CAD, hand me a beer, crayon and a napkin and i can design a machine :)
SolidWorks all the way!
Rhino 3D gets my bots built.
Gary, I do work with exact the same tools as you to develope my machines.
its the only way eh?
I prefer to design on a beermat or a fag packet. If you use a larger medium, the design gets too difficult.
quote:
pah CAD, hand me a beer, crayon and a napkin and i can design a machine :)
Woot :proud:
Anyway, I might try to install SolidWorks. Is it downloadable or do you have to buy it?
Team Gore
Download Rhino 3.0 - http://www.rhino3d.comwww.rhino3d.com
SolidWorks costs a fortune, and not even an evaluation version is availible for download. You may also want to check out these, but dont hope for anything:
http://www.solidworks.com/pages/programs/robotwars/index.htmlhttp://www.solidworks.com/pages/prog...ars/index.html
http://www.solidworks.com/pages/programs/battlebots/index.htmlhttp://www.solidworks.com/pages/prog...ots/index.html
Rhino is also an option, and a much cheaper one too.
Thanks Andy :)
Team Gore
At the RODs event in ireland Janurary 2004, Draven had several of there Saft F cells fail (i think its an f cell anyway, there the same as behemoth and stinger use). They started off with a 24v back and by the end of teh week they were down to a 16.8v pack. So perhaps the only ones really suitable for heavyweights are the sanyo 2400, 3000 and 3600.
Regards
Ian
has any one looked at the twincell NiMH line from sanyo. here is a quick comparisaon between the commonly use N-3000CR Ni-Cad Cell
N-3000CR Ni-Cad - 3Ah - 84g (size 25.2mm x 49mm)
now the twincells
HR-4/3FAUP - 3.6Ah - 58g (size 18.1mm x 67mm)
HR-DU - 9Ah - 178g (size 34mm x 59.3mm)
now thats power the only thing is I wonder if thay can produce the amp.
A quick google found a datasheet for those batteries:
HR-4/3FAUP - 3.6Ah - internal resistance 6mOhm
HR-DU ------ 9Ah --- internal resistance 5mOhm
N-3000CR --- 3Ah --- internal resistance 3.4mOhm
This suggests to me they wont be as good at sourcing high currents. They are listed as Industrial High Current though, so they might be ok for featherweights with not too high a current demand.
I think Nimh tend to be rated for lower currents than nicads, even when there internal resisitance is the same, eg the GP330SCHR - 3.3Ah - 60g - internal resistance 3.7mOhm, continuous current only 45Amps
The important thing for me for any of these though - can you find them cheap? :-)
Mark