Power issues...Electrical? Mechanical?

[Ianworld]

As was mentioned above, batteries get hot when there is too much current going through them. A bad test for this would be to connect the to terminals together. The whole thing heats up really fast. With the current you're drawing into your robot however it should never ever get hot. Maybe it could get warm, but I highly doubt even that. The fact that your batteries are dying quickly is also a sign that they are just discharging themeselves very quickly over some short. Now this short probably isn't a blatent arcing because the batteries still run for a minute and a half but that just means there is a bit of resistance in the short.

As was mentioned above i'd recomend replacing the breaker panel. Thats a pretty big task but its probably something that has to be done. There is a small chance its something in a victor or some other piece of electronics, but those usually give a pretty clear sign of any internal shorting. You could try something as simple as shaking around your breaker panel and attempting to get any and all metal shavings out of it using compressed air.

Good luck annoying electronics problems like this can be a real killer.

[KenWittlief]

Originally Posted by Ianworld

As was mentioned above, batteries get hot when there is too much current going through them. A bad test for this would be to connect the to terminals together.

YIKES! Dont do that, the battery could burst violently spraying acid jell everywhere.

If the battery itself is getting hot then you are drawing a lot of current through it. Is there any place where the battery wires go through the frame, or a hole in a metal plate, where the wires might be shorting to the frame? That would suck your battery dead in a manner of minutes, and it might only happen when the robot is moving around, or some part of the frame/drivetrain... is moved a certain way?

[Alex698]

what gauge wire are you using form the motors to the victors and the victors to the circuit breakers? i know the motors (CIM) have 12 gauge wire, then we used all 10 gauge anyways. Plus check your connections on the 6 gauge wire. the copper brackets like to come lose even if they are taped.

[lukevanoort]

I thought of something else, check your 120 amp main breaker. We ripped one of the mounting holes out ours. (The inspectors didn't notice, nor did we have a problem) So, they might not be all that durable. I really doubt that the Anderson has a problem, but check it too. The compressed air idea is always good, so if you don't have a air system, making your own is worth while. (This is what we did with old compressors)

[Rhubarb]

Thanks everyone for the great ideas and suggestions.

The robot is on it's way to the Boston regional and we have not been able to reproduce the problem with the spare parts we have at the school. We were able to test the motors and transmissions. They are assembled correctly and running freely with no obvious problems with the CIM motors. Right now we are leaning towards a problem with the breaker panel or the wiring between the battery and the breaker panel. Hopefully it will be a matter of swapping out a few electrical parts to get us running at 100% again. I'll post an update of symptoms and/or a solution as they develop.

[Al Skierkiewicz]

First things First...DO NOT SHORT THE BATTERY TERMINALS TOGETHER! Explosion may be the result.

Everything that has been described thus far leads me to want to look at the mechanical load. But let's clear up a few things first so you won't be mislead by the data. It is illegal (under First Rules) to connect two motors of any type to a single speed controller, but it won't produce the problem you have. Running any of the Chalupa motors, no load, will cause brown outs when switching between forward and reverse. Remember that a motor that is not moving is "stalled" and stall current is 134 amps for the small Chalupa and almost 100 for the large. Changing direction on any motor runs it through the zero speed condition of stall. If your battery leads are hot but the leads from the main breaker to the breaker panel are not, you likely have a loose connection on the battery, damaged contacts on the battery disconnect or a short to frame somewhere ahead of the panel. Since you are showing a breaker fault on the panel but nothing else seems to be a problem, discount the red light light as a bug in the panel. What that leaves is the probability that your two motors in the transmissions are running in opposite directions. You must check the direction by disconnecting one of the motors and giving the robot a forward command. Check the direction then disconnect the first motor and reconnect the second and check direction again. I believe the large and small Chalupa motors have a different direction when fed the same polarity voltage. The small Chalupa is counter clockwise. Since the current draw and battery voltage anomalies were nearly identical with the robot off the floor, everything is pointing back to the transmissions/motors. BTW, when the motors are fighting each other (going in opposite directions) there is a very distinctive and unnatural sound generated in transmissions.
Remember that the RC cutouts and goes to backup battery when the main battery falls below 8 volts which will occur during heavy loads. The main breaker, although rated for 120 amps, can withstand 600% overload for several seconds without trip. Similar trip characteristics on the 40 amp breakers but they get very hot after repeated tripping. A four motor drive with all motors running near stall will easily draw 400 amps.
Contact me via PM and I will give you my eamil address in case you have a problem on Thursday.

[KenWittlief]

Al has provided a great check list

and it made me think of one more possibility. You have not stated in the list of problems whether you are using any type of PID closed loop / feedback to control motor speed or robot direction

BUT if you are, and your PID loop gains are set too high, the commands going to the motors could get very wild (extreems) even if the robot is not moving around much

normally if you have the PID gain too high the robot will be twitchy, will overshoot and tend to oscillate, but you might not see those symptoms. The thing that makes this difficult to test is you cannot simply put a scope on the PWM outputs to see what the control signals are doing (if they are going wild). You would have to capture them with a printF statement or some other SW debug tool, then drive the robot smoothly and see if the motor PWM outputs are going 244, 3, 220, 12, 254, 0.... back and forth all the time.

this would be almost the same as applying full power to a stalled motor. It would draw a huge amount of current, even though the robot is hardly moving.

[Rhubarb]

We are not using any control or feedback loops for the drive. We are using the bells and whistles camera code provided by Kevin Watson with the only changes being to map the correct joysticks to the correct motors.

[Peter Matteson]

Not that it necessarily applies directly to this thread, but I intend to bring most of the necessary tools for diagnosing these types of problems to UTC this weekend. DC clamp meter, non-contact tachometer, and IR temp probe if needed, couldn't get the portable o-scope however. If you are at the UTC and would like to use these see me in the 177 pit.
Pete

[Caleb A.]

hey ive recently heard the a tight bend in your battery wire will dramatically decrease your power flow for battery to system and create great amounts of heat. u might check on that it is just a thought and i could be completely wrong. Good luck with yur problems