Re: Tank Track
 

Since the only batteries allowed for the VEX official comps are the Vex rechargables all the teams will have buy them before the NZ regional.

Later it might be worth asking Vex if we can use their batteries but our chargers.

I take it the Vex only battery rule is so everyone has the same battery capacity.

Our team is using Vex only parts as it's saves building a robot then having to tear it apart and rebuild with Vex parts close to the Regional.

Have you guys got many outside mentors? By this I mean not parents /teachers.

Re: Tank Track
 

Symbiohsis doesn't really have any mentors we could call on people if we get really stuck but at the moment us the students seem to be doing just fine. When we get to compete in FRC we may get mentors in to help (we have been making contacts with people in different ares E.g room sized CNC machines:D) but as the person on our team that designs, with the help of everyone else's input, what our robot will be like then builds the majority of it (i am training 3rd formers up on how we build them) i think the VEX robotic system is very easy to use and very versatile. Also reading over CD for hours everyday is hopefully giving me a better understanding of what people are doing and of new and interesting ways to address problems:)

Re: Tank Track
 

haha, i probably have something lying around somewhere, or could improvise something. but our head mentor is likely to hunt one down anyway. we're definitely looking into it, just as soon as we can afford it.

sounds like you're pretty well equipped ;) we have a couple of metalwork rooms and a brill computer lab, but thats all on provision that there isn't a class in there :rolleyes: we're going to try to kick them out during FRC though.


really? i thought since the holder/connector for the AAs was VEX we'd be alright. i'd better inform my team of this one

we're doing the same. partially due to lack of non-VEX equipment :p


Phr34kR - your team obviously have a lot more experience than ours :yikes: you're doing brilliant in the competitions, too. I look forward to seeing what you guys will come up with for Lunacy.
Yes, Chief Delphi is definitely a huge help for us who dont know what we're doing, and makes the life of all our designers easier
"how do we do this?"
"check Chief Delphi"
"what about this?"
"Chief Delphi"
"And-"
"CHIEF DELPHI"
:D

Re: Tank Track
 

Yea it seems strange why your not allowed AA batteries at first but when you think about it if someone was to use maybe lithium batteries they might get an edge over the competition power wise (it would be expensive but doable)
i know that for the Westlake competition we had to change the batteries on the winning robot every match (something about those two lead bricks i added to the robot...)

Re: Tank Track
 

I guess so, but if they don't want us using disposables, they should have to provide us with the rechargeable :p

yes that would do it :p
I think Philup used more batteries up because of its weight than some of our robots have, but we fortunately had managed to find some really good disposables that lasted us ages (tank tracks weigh a ton :yikes:) but i think the pneumatic robot the boys made only went through one or two sets
we have a huge stockpile of 'controller batteries' that are too weak to run the robot but perfectly fine for the controller :p)

Re: Tank Track
 

You can use non-Vex Chargers and I very highly recommend buying one (often designed for use in other hobbies) that lets you do the following

• Charge batteries with different numbers of cells in them
• Charge NiCad batteries (and optionally other types)
• Discharge batteries fully
• Charge batteries at a rate you control
• Display how much charge has gone into (or come out of ) the battery
• Charge/discharge more than one battery at a time
• Measure the output voltage of a battery when unloaded AND when under load (when being discharged)

Buying one with these features will be some of the best money you spend.
You should be able to buy them for under $150 US.

Blake

Re: Tank Track
 

US$150 is close to NZ$300 btw. To NZ teams Surplustronics seems to be selling 7.2V NiCad battery chargers for $25 although they are only 1400mAh chargers though so im not sure how they would go charging the 2000mAh VEX batteries though?
I had a quick look through my Jaycar catalog and there doesn't seem to be anything in a decent price range. (one for $179.90 that would definitely work and another for $71.90 that may work but there isn't enough information in the catalog to say for sure i would assume so though but with the cheaper one you will have to also buy a 12V supply.)

Re: Tank Track
 

Hi where did you find out they are 2000mAh batteries? Is it written on them?
The website doesn't mention this on the page the batteries are on?

Having this info may help get alternative batteries.

Re: Tank Track
 

Hi i wrote that from memory but yes it does say on them and i can confirm that the 7.2V VEX NiCad's are 2000mAh and the 9.6V ones are 1000mAh (i now have a bunch of them in front of me. i wouldn't think you would be able to buy them here for much cheaper than NZ$40 a piece but then again i haven't been into buying them here much. I went into airsail to buy a PWM cable (buy them from VEX they are much more expensive here, $20 a cable.):ahh: And from memory the batter packs were more expensive than the VEX ones.

Re: Tank Track
 

Yes, it adds up to a fair bit of money in the end.
yeah i wouldn't be surprised if it were cheaper to get them from VEX with the way prices are going here lately.
I reckon the best way to go is the power pack kits, with charger and one battery of each kind. but when running two robots at a time, will we need a spare battery or will they hold all competition?
cos if we needs spares it would add up to around US$200 or NZ$340 (approximately) plus shipping, plus we'd have to find a powerpoint adaptor for them (although that shouldn't be as hard)

Re: Tank Track
 

We run two robots using 5 motors and a servo each we brought 2 power packs and two spare 7.2V batteries plus one spare 9.6V (you wouldn't really need the spare 9.6V one (we haven't had to use it at a competition yet) so really it would cost you US$140 for enough batteries for the competitions here plus the input into the charger is quite a big range something like 7-14V (don't quote me on this though i will edit the post once i have checked in a few minutes) Symbiohsis has gotten away with four robot batteries two transmitter batteries and one charger (the charger will only charge one battery at a time though even though it holds four:confused: ) for the last competition and we seem to have done okay :cool:

Sorry 11-20V dc input into the chargers (grab a 2A 12V power supply from jaycar for about $40 and wire the two chargers into one power supply - outlets are limited at competitions.

Re: Tank Track
 

great, thanks phr34kR.
we have our first meeting for the year on Saturday so i will bring the battery issue up there, and hopefully we can find some money to get them :)
so you did actually change the robot battery during the competition? darn there goes my budget money-saving ideas. ;)

Re: Tank Track
 

Yes, that competition went really well. I was so thrilled to see Phillup get so far in it, especially after the trials of building him!
I never thought I would get into building chassis, but I guess that's one of the beauties of FIRST - steep learning curves.

I'm not sure whether I thought there was more or less variation in the designs of the 'bots between the competing teams this time round. I did notice however that there were less quirky experimental ones and more that worked consistently throughout the matches.
I miss the quirks, because it made it entertaining to watch, but I think it goes to show that the teams here are really starting to focus and hone skills.

Correction dear, when we get to Dalhas :D

Good to see my photography gets put to good use :P
Sorry about the delay on the photos, technical difficulties with the camera and it's cable.

And I agree, the banners at the competition looked fantastic

The $2000 was actually a grant from the local ASB branch which was sourced by our principal. Unfortunately it didn't even cover the three VEX kits. It bothers me that our Mentor is spending so much on our team, though I know it's his passion, and that's something I would really like to change this year.

Re: Tank Track
 

Bwahaha, yes excellent photography G :p and what do you mean it was great seeing Philup get that far? :yikes: we knew he would from the start!!
except for my multiple heart attacks

same diff :P

it didnt?? he told me it did!! :O

we'll have to find some sponsors this year...

[Ignoring the When comment]

Re: Tank Track
 

In the middle of this long post, Link to VexLabs Forum you can find some calculations for how long a battery can last across a series of VRC matches. In practice, most folks swap them more often than the simple calculation predicts is necessary.

How well the battery has been treated (Don't slap them on a charger after every use. Fully discharge them before charging them (down to around 5 V)) and how old it is will strongly affect how it stands up (does its voltage dip) when hit with a high demand for current.

Blake