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those are @ 24v, tracks wont use much torque for turning thanks to my special track design, that actuator is pretty small one and it is for LW lifter
i would prefer NI-MH packs, because those wont need
discharging and other special things, but if those doesnt give enough current, i have to go with nicads
intercooled Ni-MH battlepacks wont give enough current?
how long can battlepacks be used before they need replacing?
Well first off Ni-mh will not give enough current
Ni-Mh will and can....
Erm - no they wont !!! 2 x EV Warriors at 24v can theoretically draw 198 amps each at stall. Allowing for resistance of a Victor 883 controller and cabling, the most each will draw is around 130 amps each, a total of 260 amps.
In reality you wont see this much as youll never work them that hard, so lets allow for wheelspin etc and call it 180 amps - thats still way more than a string of 3300mAh NiMHs will deliver.
The GP 3300 is good for about 45 amps cont. output, but doesnt have the ability to peak much above that. In contrast a Sanyo 2400CR will deliver a similar cont. current of 50 amps, but can peak to close on 100 amps (as measured on Vortex on spin-up).
If youre wanting to run 24v I would suggest 2 x 24v NiCad Intercooled Battlepacks in parallel made up of Sanyo 2400CR Sub-C Cells. You *might* get away with a single pack made from N3000CR C-Cells, however that would depend on whether youre fighting a 3 min or a 5 min fight. 3 min and you should be ok.
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
Agree with Ed, although the 2400 cells are now old technology :-) with the new 2600ni-mh cells- they apparently even have a higher max current that the 2400s which is surprising. I had some trouble believing it but everyone I know whos used them confirms this. So you may as well et them over the 2400s. I suppose whats finally happening is that the money being put into ni-mh is finally paying off, as in theory they are a better chemistry than Nicads, its just its traditionally been a bit difficult to get the most out of that excellent power density. Anyway, Li-polys here we come :-)
I didnt say all that would be needed is one 3300mah ni-mh battery, infact 2 GP 3300mah ni-mh packs in parrellel would probably run fine with two EVs (taking into account most linear actuators take tiny amounts of current). From speaking to JH-Q before on msn, he does have much easier access to ni-mh batteries than ni-cad ones (although he only has easy access to cheap packs).
Should he use cheap ni-mh packs, it would be best to experiment which capacity suits the motors best for certain run times. With cheap ni-mh packs your probably looking at 6000mah combined capacity minimum.
Ewan Compairing Like with like:
Ni-cd 3000mah: Maximum Continious: 80amps
Peak: 150amps
Ni-mh 3000mah: Maximum Continious: 35amps
Peak: 50amps
Thats for the same capacity now for the same weight:
Ni-cd 2400mah: Maximum Continious: 50amps
Peak: 100amps
Ni-mh 3300mah: Maximum Continious: 45amps
Peak: 60amps
Simply put Ni-cds wipe the floor with Ni-mhs when comapiring current and capacity or current and weight.
Quite simply he would be better off with Ni-cds whether he goes for a single string of 3amp Ni-cds or two strings of 2.4amp Ni-cds.
Regards
Ian
Your comparisons are at the least, dated, ni-mh is almost at a par with ni-cad weight-to-current ratio. Your comparisons also dont allow for specific run time, you should allow for a 6 minute run time in the least (also 6mins is a 10th of an hour so it makes calculations easier :))
GP ni-mh cells at 3300mah (and other international other brand cells) can Peak 100amps, and not your suggested 60
Also, you need to take into account the actual energy capacity, and not just the short-period output ability. An EV may take short current spikes, but good quality ni-mh cells can cope with that.
(the debate continues :))
GET A LIFE!
Mr Stu
I can confirm from first hand experience that ni-mh cells or at least specific brand new types can and will deliver very high currents.
The cells we use in Typhoon 2 are ni-mh and they can almost certainly give us the required current! From our on board data logger we worked out that at one point in the series 7 final they gave us 400 to 500amps and the voltage dropped to 12v.
If you choose the right ni-mh cells they will out perform ni-cad.
i was thinking normal battlepacks...but where are they?! http://www.robotcombat.com/marketplace_batteries.htmlhttp://www.robotcombat.com/marketplace_batteries.html
no normal battlepacks?
then i have to go with intercooled packs...
these batteries wont be under heavy conditions, it is finnish robotics :)
the most powerful thing they have to encounter is six drills, others go with two or four drills :proud:
hey, how big wire you recommend for those batts and general wiring for that robot?
Use the Design Your Battery Pack feature and select the type of cells you wish to use (2.4amp ni-cds or 3amp ni-cds) and select the formation and voltage. You can even select the size of wire and connectors used.
However be warned these packs are now welded construction and not soldered like in the past. It would be best to go for the intercooled ones as they are soldered and therefore can supply more amps.
As for wire size. In my featherweight I use 2.5square flexy flex throughout. Its not as good as the wet noodle wire available but is cheep and I can get it in my main street. For your robot I would recomend 4-6square for safety. Now the americans dont use square but here is a rough guide:
2.5sq: 14.
4sq: 12.
6sq: 10.
Robot combat sell Deans Wet Noodle 12 Gauge Wire. This in my opinion would be best suited to your application as it can take the current and it incredibly flexable. It really has to be seen to be believed. Ed had some at gghw and you could tye it in nots and it would stay there. Its amaizing.
As for connectors you will probably need to either use some of your own or else use the 75amp powerpoles.
I hope this helps.
Regards
Ian