<R12> The only allowable sources of electrical power for a VEX IQ Challenge Robot is any single (1) VEX IQ Robot Battery or six AA batteries.
A while back I saw a VEX IQ kit in a toy store that was basically a stripped down super kit. On the box it advertised that it was competition ready. I thought that was odd because it didn’t have a rechargeable battery, it took six AA instead. I guess it’s nice that people who bought it thinking they could compete aren’t disappointed, but on the other hand AA batteries typically perform better than rechargeable batteries. Hopefully they make a AA battery holder available for individual purchase, I don’t like the idea that teams can gain a competitive advantage from a part only available in a $300 kit. And on top of that the AA batteries become a money sink, benefitting teams with larger budgets. It would be nice if the rule was changed to only allow rechargeable AA batteries, it would save money and reduce the advantage gained by using AA batteries.
It’s really not going to be an issue. You can draw a lot more current from NiMH cells than you can from alkaline so worst case is, people will have higher capacity NiMH cells in there which will be irrelevant as the matches are so short. The standard IQ battery is 2000mAh, someone may use 2700mAh but wouldn’t get a competitive advantage. Alkaline batteries are no good for this application at all but I would be interested to see how Lithium Iron Disulphide batteries perform. I have an IQ AA battery holder here so at some point, I’ll do some tests with alkaline, NiMH and Lithium AA cells versus the standard IQ rechargeable pack.
My concern isn’t about the capacity of the batteries, as you mentioned with such short matches it doesn’t make a difference. It’s the fact that six AA alkaline batteries is 9v while the rechargeable battery pack is 7.2v, potentially giving it more power (pardon the pun). If the AA batteries were rechargeable they would only be 1.2 volts each which would make six of them 7.2v just like the the rechargeable battery pack.
It won’t affect the speed at which the motors turn because that’s kept in check with the encoder, but it will probably increase the stall torque of the motors. If you run a test that’s what you should check.
I have done some testing - I was going to do something nice and scientific but before I did, thought I would do some “real world” style testing just to get a feel.
The test used the standard NiMH battery supplied in an education style Super Kit. For the primary cells, I used the AA battery holder found in the retail style kit and the following cells which were brand new taken directly from the packet and well within shelf life:
I used the demonstration Bank Shot robot that I built at the start of last season which used 6 motors - 2 drive, 2 flywheel, intake and conveyor.
Test 1 - Standard VEX IQ NiMH rechargeable battery
Plenty of power to run all the motors simultaneously. No noticeable change in drive speed when flywheels are running. All balls can be cleared with no noticeable loss of power/speed and ramp climbed with flywheels still running
Test 2 - Lithium Iron Disulphate AA cells
Robot noticeably much slower to drive than with the NiMH. Noticeable further drop in speed when flywheels running but would continue to run for a few minutes with no further decline in performance. Poor shooter distance and not capable of climbing the ramp
Test 3 - Alkaline AA cells
Initial performance was very similar to the NiMH but this lasted about 10 seconds before a noticeable drop. When running the flywheels and intakes, the red battery warning LED on the brain starts to flash and the battery level indicator appears low until you turn off some motors. I doubt you could complete a competition match with alkaline cells.
So in conclusion, not a problem. Primary cells just can’t provide the current needed. I didn’t bother to run the test with NiMH rechargeable, I don’t think there would be a noticeable gain although I am sure someone could draw a little more current if they spent a while selecting the best and lowest resistance cells they could find.
Aloha,
This is definitely to bring up to VEX as far as the legality of using this battery pack in competition. Based on my understanding of the rules in regards to using Hex Bug parts in competition is that no electrical parts would be allowed to be used. Motors and brain are definitely on this list. But I would assume battery packs also as it is an electrical component. If this were legal than technically the thin wires in the HEX Bug kit could be used to tie parts together. I think this is something definitely to bring up for an official word. I’ll go ahead and post it in the official rules section. I hope that will get us the answer that we need. Thank you for bringing it up.
The battery pack in question isn’t from a hexbug kit, it’s a battery pack designed to fit the VEX IQ brain and is available in some kits. In previous years it explicitly stated in the rules that it was not allowed. This year it is allowed, that was my concern but I trust calvc01’s tests and it looks like it won’t be an advantage at all.
It kind of is Bez, the retail VEX IQ kits carry the HEXBUG branding on a flash on the corner of the box. The AA battery pack from these kits is legal for the VEX IQ challenge but the one from the other types of kits (shown in the below link) would not be and would not power any of the VEX IQ electronics anyway as they have totally different methods of connecting,
ipnavigator - I have quoted the rule from the manual for reference: **<R12> **The only allowable sources of electrical power for a VEX IQ Challenge Robot is any single (1) VEX IQ Robot Battery or six AA batteries.
Since the only way to connect six AA batteries to a VEX IQ Brain is by using the VEX IQ AA battery holder, the intent of the rule is clear.
Aloha Surgeon,
There are a lot of parts in VEX IQ that we wish would be sold separately. All long 1x beams, long 2x beams specialty HEX Bug Parts, and the list goes on. I hear you though. We’ve been talking about it for years.
From the Bank Shot Inspection manual from Bank Shot. (http://www.roboticseducation.org/documents/2014/11/vex-iq-inspectors-guide.pdf) – I haven’t been able to find this year’s Inspection Manual
<R12> Only source of electrical power is one (1) VEX IQ Battery Pack, even those not connected
• AA batteries may not be utilized despite the option existing in certain kits.
<R12> The only allowable sources of electrical power for a VEX IQ Challenge Robot is any single (1) VEX IQ Robot Battery or six AA batteries. [INDENT]a.Additional batteries cannot be used on the robot (even ones that aren’t connected).