9v battery problem and field control

hi guys, i only just remembered something from the last comp we were at, if the vex backup 9v was connected to the vex cortex, it wouldn’t connect to the grid for some reason, is there a reason for this, have i done something wrong or has it happened to any of u guys ?
Plz respond with help

Team 5119
AKA
The Bodge Jobbers
team5119.webs.com (still under construction, lacking content and pages)
United Kingdom
Vex UK Nationals : Energy Award

Strangely we felt that we had these sort of problems, it’s important to ask the referees how to connect.
We asked various field techs at worlds and they said that it is usually attributed to these sort of issues.

when we were at nationals, everyone just kept saying unplug your backup battery and don’t bother plugging it back in … so we did , but a couple of times communication between cortex and transmitter died (probs because no backup battery)

I do believe that I had read somewhere in the past that after a match, you need to turn off your joystick, cortex AND disconnect the 9v battery.

[Speculation]
It’s my understanding that the 9v battery maintains a wireless connection between the and joystick. So it would make sense that turning off the cortex simulates losing connection to the 7.2v battery. The 9v would try to maintain a connection, but the joystick is off. This would then cause issues when you try to recconect your joystick and cortec for your next match…
[/Speculation]

That’s all just my understanding/inference. After 10 minutes on google I couldn’t find the source of my original statement, so take it with a grain of salt. But it can’t hurt to do it anyways.

alright … i think i might just recondition our space cortex and see if it is the same on that … it might just be a firmware glitch … but yes … the 9v battery maintains the vexnet connection, also … i found out the paperwork from the uk nationals, and there is nothing about the 9v battery mentioned in the “connecting to vexnet and use in game section”

Well, I doubt its a firmware glitch. I understand your issue as our team struggled with it too. For a while we just ran our robot without it, but any ramming would cause our connection to fail so we plugged it back in, disconnecting it after each use, and everything is fine now.

As with all things there is a procedure.

At the end of a match.

  1. Disconnect from field control, ie. pull the field control cable out.
  2. Turn off the joystick.
  3. Turn off the cortex

If you do this then there is no need to disconnect the 9v battery.

Now, no one remembers so most just disconnect the 9v battery as you describe.

There was a thread last year discussing the need for the 9v battery at length. Using a well charged NiMH or new Alkaline backup battery is important, a discharged one can cause problems.

my team had the same problem. we found out if your 9V is dead it will disconnect from the field. try to replace to battery.

we have 2 rechargeable 9v, they work fine … i haven’t had a problem, they are charged and they read full on the battery tester …

Per this quote from an unnamed but knowledgable source,
There is no point in using a 9V backup battery without something plugging into the Game-port of the joystick. For example, BEST Robotics isn’t using the Game port or field control (just 1,2,3, GO), so BEST will be dropping 9V battery use this year.

If you practice without a game port cable, you might as well leave 9v unplugged.

For VRCC (College, where custom electronics are allowed),
I prototyped some 110V light switches as power switches.
I couldn’t find a cheap 3pst switch, so I just set up 3 of them for
Cortex power, expander power, and 9v power.
That way, I don’t have to mess with pulling plugs, or tiny switches,
and when I turn them off, I know they are off.
If some college team chooses to use similar custom switches,
be sure to check that your switches are rated for DC, and > 8A.