Thanks for the number.
I have tested with a NiMH rechargeable 9V. I connected the Cortex with a main 7.2v and the 9v one, turn on Cortex and made sure WiFi connected with joystick, then switched off the Cortex to simulate a current over-draw reset and/or forget-to-unplug-backup type of situation. The 9v kept the WiFi connected for about 9 minutes. Reasonable based on your number. The NiMH 9V I have is rated 175mAh. I will try with an alkaline 9v when I have chance.
There’s some data on 9V alkaline here http://www.powerstream.com/9V-Alkaline-tests.htm
Obviously the 9V battery is only supposed to keep the cortex going for a few seconds so I think the important thing is to start each match with a freshly recharged battery.
Good info, save me ~$3 to burn a 9V alkaline. Based on these tests, alkaline should be better but varies widely among brands.
We use Duracell.
For alkaline these look like the best value http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4536873&CatId=2583 (just one site of many that have them at this price), certainly better than the $6 for two batteries most retail outlets sell them for. For better value long term NiMH will work out cheaper.
That’s a GREAT deal. Thanks for the website, I will pass it on to my coach!
Do a google search, you can find the same battery elsewhere, that site is just one example. I also like Rayovac but at the end of the day I doubt there’s that much difference between the name brands.
“but at the end of the day I doubt there’s that much difference between the name brands.”
So agree! Thanks for all you help!
9 volt batteries can be very important, i played an entire match on it last year, because i forgot to plug in the main robot battery we won…
what does that have to do with the 9v battery?
the results would have been the same if you havent had it in
or maybe it will because you would’ve noticed the robot lights not on…
i turned the robot on with only the 9 volt battery plugged in and played with only the 9 volt plugged in
there is no possible way a 9 volt battery has enough current to power 10 vex motors maybe the 9.2 volt battery pack but not just the 9 volt battery
I agree. That is just not right. How did you do it?
Please clarify your comment for us as technically this is impossible. Perhaps you have a different control system.
This thread is discussing the 9V PP3 style battery used as backup for the cortex. If this is the only battery connected then there is no unregulated power available for the motors so the motors cannot run. There is also no 5V power available for the sensor ports.
The 9volt battery for the Coretx Controller is to prevent a Brown-Out condition for the Microcontroller during high Power demands. To the best of my knowledge, you can not run the entire Vex robot on a 9volt alkaline battery, even for a few seconds. Leaving out the fact that Alkaline batteries have a high Internal Resistance ( They won’t Discharge very quickly, which is critical for Motors and Servos ), the Stored Energy in a standard 9volt battery is very limited…
“Captain, I can not change the Laws of Physics…” - Lieutenant Commander Montgomery Scott
( from the Star Trek Original Series episode The Naked Time )
He didn’t say he did well with only the 9v battery, or that any of the motors moved.
Only that he “played”.
Well, technically, you don’t even have to have a robot on the field to “play”. Someone from your team just has to be up at the field.
I agree. How did it really happen?
no, i think there is a rule about that
if you dont have ur robot physically on the field, you will receive 0-0 sp/wp
(only you, your alliance still gets the points)
Well, maybe you’re right. Though I remember that at some of the competitions that I went to, teams who basically had a dead hunk of robot were allowed to just send a representative to the field so that they had more time to fix whatever was broken.