While at the BAE regional we ran into a problem and we’re wordering if anyone has any ideas what could have happened.
We had our robot on blocks in our pit so it wouldn’t move. We were using a 2003 battery to power the robot. The 7.2V backup battery was charged and installed. While operating the 4 motor drive train we noticed the following problem:
The battery appeared to be pulsing out power. Our RC would reset itself about once a second. Causing us to loose control of it. We did notice that the battery had loose terminals. But would that explain the pulsing? Why did the RC reset? I thought it had a backup battery? Anyone have a clue what might have happened?
It might be that something was shorting out every once in a while. Maybe the backup batery was accidentally close to something. Did you ever actually measure the current at the connectors of the RC to the power? It might be that something was totally weird with the code and it was reseting itself.
In any scneario involving problems with the battery, it still should not have reset because of the 7.2v back up battery. Not even a loose terminal should cause that. Good thing it didn’t do it during a match!
If you changed to the new batteries and the problem goes away I would not use the old batteries.
We had to set one match last year at Nats because of a bad cell in a borrowed battery. So now we pre-test all of our batteries.
One of the mentors brings in his equipment that he uses at work that test the oxidation of the battery plate and checks the contacts and everything. The tester is from Midtronics (FIRST sponsor) and it has a printer which prints of about everything you would want to know about the battery. It’s a neat little product with a big price tag.
I would avoid that battery at all cost. I would probably toss it so that some member won’t accidentally switch it in to the robot before a match. Because setting there with no power is no fun.
Lead acid batteries can actually go bad rather quickly if you’re not careful. If you constantly keep them charged up and stuff, they’ll last you a decently long time.
On the other hand, if you run the battery flat, like I know many robots can do, and leave it that way for a few hours, it’ll sulfate and die. So the moral is, keep your batteries charged at all times.
I belive you may have more then just a bad battery here.
When was the last time you charged the 7.2v battery? Are you completely absoultly sure that it was charged during this?
It’s acutally pretty easy to kill that battery. If you just powerup the bot with out ever establishing a link to the OI it will just sit and listen till it kills the battery or someone presses reset. I also noticed that the connector on the RC and battery are kinda cheesy. Perhaps it has come loose?
As for the battery ‘pulseing’ power, I would very carefully check the breakers. It sounds like there may be a short on either your RC circuit that is causing that breaker to trip. Did you hear any ticking noises? Perhaps the RC has an internal fault.
Before you toss a battery, eliminate all other possibiltys. Batterys not be cheap.
Yes, I checked the backup with a volt meter; it was charged, 7.3V I believe. They were only last years batteries so it’s not a huge loss. We just wanted to keep the 2004 batteries on the chargers while we use the old ones in the pits. I couldn’t hear a ticking noise over the starting and stopping of the 2 drills and 2 chips in our drivetrain.
Since this problem never occurs while using a 2004 battery I think we can rule out an electrical problem on the robot.
My guess- We were tethered at the time. Using the RC to power the OI. Could the reseting I was seeing the result of a loss of communication with the OI?
Yes, this is a possibility. More likely though is that your robot uses a high amount of current when up on blocks in the pit. Much more than it does on the floor. (Strange but possible) More likely is a combination of the loose connections on the battery and the backup not fully inserted in RC. When you checked the backup was it in place on the RC while the RC was running? If not, you may have had a discharged battery. Innovation First was checking backup battery via modem stream and informing teams of low backup battery condition, so if you were competing OK then your backup was good when you went onto the field.
During build season, we were testing our robot with a very poorly constructed wiring system (my fault). The connector from our main battery to the breaker block was not very strong. We also had a 7.2V backup battery connected, albeit one of a much higher capacity than Innovation First’s.
We were still able to reset the controller easily. Whenever the connector from the main battery to the breaker block slipped, the robot would stop in its tracks and the controller would reset. It appeared to us that switching from the primary battery to the backup battery usually (3 out of 5 times) caused the controller to reset. The reset then required the full radio re-sync and other processes. We thought about the matter, and decided not to worry about this, because if the main battery was unable to power the robot, for whatever reason, we have greater concerns than keeping the controller up and running.
Btw, we were also able to start the controller with just the backup battery. I have heard many teams were unable to do so. I am not sure of the reason why we were able to.
