Battery Drain Issues

[cgredalertcc]

Our robot seems to be eating batteries like crazy. Running only our drive motors and RC on the main battery at high speed (13 meters per second) we can only make a lap or two before turning becomes difficult. The motors aren't in horrible shape because they aren't getting very hot. We are running everything well lubricated. The only issue I can see is that theres an extraordinary amount of sideways friction. We started with 6 wheel drive (center wheels 2x6 IFI traction s with wedge top and 4 omnis) but we changed the read omnis to 1x6 traction wheels, thus making turning harder and more accurate. Still it shouldn't eat a battery like that, should it?

[EricVanWyk]

Can you please measure and post the following 4 voltages? Please use a separate multimeter.

Fresh Battery Voltage
Fresh Battery Voltage with motors spinning

Drained Battery Voltage
Drained Battery Voltage with motors spinning

[cgredalertcc]

Originally Posted by EricVanWyk

Can you please measure and post the following 4 voltages? Please use a separate multimeter.

Fresh Battery Voltage
Fresh Battery Voltage with motors spinning

Drained Battery Voltage
Drained Battery Voltage with motors spinning

Sure I'll do it tonight at the meeting I'm currently in study hall on my laptop in a robotics friendly teacher's room.

[Joe Ross]

Are you sure that you are designed for 13 meters per second? That's 40 feet per second or twice as fast as the fastest robots typically go.

Plugging your details into JVN's drive train calculator: http://www.chiefdelphi.com/media/papers/2059

I assumed 2 CIM motors per side, 6 inch wheels, 1.3 coefficient of friction, and a single gear reduction of 10 and 35 (to get to 40 fps). This shows a total current draw of over 1000 amps. If all the right circuit breakers were installed correctly, you should be tripping them very quickly.

Did you mean 13 feet per second

[Al Skierkiewicz]

Charlie,
From your description, you are running a tank style drive with multiple motors and multiple wheels on the floor. In this configuration, all of your drive motors draw near stall current when ever you turn. (4 motors could easily draw 400+ amps) A sure sign of high wheel friction in turns, is the tendency for the robot to "hop" through a turn.
The fact that your drive motors are getting warm in just a lap or two is an indication that something maybe wrong in addition to the high friction in turns. If you are using multiple motors on your transmissions, are you sure that each motor is running in the right direction? Depending on which transmission you use, the motors run in the same or in opposite directions. Try removing the 40 amp breakers feeding one of the motors on each side of the robot and see if the robot runs correctly. Then swap motor breakers and see if the robot still runs correctly. As an additional check, try moving the wheels by hand and see if there is any significant friction in the drive train. Also try driving the robot with the wheels off the ground and see how long a battery lasts.

[cgredalertcc]

Originally Posted by Joe Ross

Are you sure that you are designed for 13 meters per second? That's 40 feet per second or twice as fast as the fastest robots typically go.

Plugging your details into JVN's drive train calculator: http://www.chiefdelphi.com/media/papers/2059

I assumed 2 CIM motors per side, 6 inch wheels, 1.3 coefficient of friction, and a single gear reduction of 10 and 35 (to get to 40 fps). This shows a total current draw of over 1000 amps. If all the right circuit breakers were installed correctly, you should be tripping them very quickly.

Did you mean 13 feet per second

yes thats what i meant that is the second time I've done that this year. I blame my physics teacher

[cgredalertcc]

Thanks for the help the issue was resolved we had a bad connection at the main breaker, along with all of our batteries not being at peak charge. The drive base performs wonderfully and we should have some pics or a video up soon.