Here's a question for the Brushless experts

[crazyjr]

I got my VXL back from Traxxas today, they said it worked for them so no repair was necessary. I got it in the stampede and works great.

I noticed something with the eagletree while testing, I saw a draw amperage at times of idle that shouldn't be there. I talked to Traxxas support and they were not aware of it, sio i told them i'd reprogram it and get back to them about it.
After i reprogrammed it it showed a constant 4-5 amps at idle, the test was idle, then foreward, then idle, then backward, then idle then worked the trim fore and back till wheels moved. Not sure of what i was looking at i tested my T4 with MM 4600 system, it showed the same thing But at 1 amp.

During both tests, while working the throttle i didn't notice much, but working the trims, I saw the amps drop very slightly. The only thing i could think of was the caps were bleeding off into the battery.

My question is. If idle do the caps bleed of into the battery? and if so, does size matter in holding the energy? One thing i do notice between the two systems, is the caps in the MM are about twice the size of the VXL, possibly thats the reason

thanks for reading and responding, and sorry for the bad typing

[SpEEdyBL]

Did you try it without the servo connected or the esc off?

[BrianG]

Caps will only charge up to the battery voltage and do not present any kind of load to the battery by themselves once charged up (and that takes milliseconds).

What is probably happening is that your throttle trim is set so it is sending enough voltage to the motor to draw current, but not enough to make it turn under load - essentially "on" a tiny bit. Try removing the pinion and see if the motor doesn't turn. I suspect it will since there is no more load (simply from the drivetrain) holding the motor back. Then, adjust your throttle trim slightly until the current drops to near 0 and/or the motor stops.

That said, 4-5A should be enough to make the motor turn regardless of load. At only 2s, that's between 30W and 37W of power being sent somewhere. If the motor isn't drawing the power, the ESC must be and something should be getting at least warm.

Either that or your eagletree unit is miscalibrated and is seeing a current that is not there, which is weird since it uses a hall-effect sensor for current (as opposed to a series shunt resistor to measure V drop).

[crazyjr]

It was 3s, and i moved the trim both ways an equal distance, before it moved. The throttle trim is centered and has been reprogrammed to the center. When i moved the trim, If you are right, it should have dropped towards zero before going back up either way. It never dropped till the motor moved

SpeedyBL, No i did not remove the servo from the equation

[BrianG]

Hmm, then the ESC must be always energizing the coils trying to spin the motor a little (maybe trying to get a feedback signal?), but not quite enough to get it to move.

What happens when you remove the pinion from the motor (unloading it and able to spin freely)?

Either way, this is definitely a system where you don't want to forget to unplug your batteries even for 10 minutes!

[crazyjr]

Good thing its got a Lipo cut-off. The MM 4600 did the same thing with the same test, it was doing about 1 amp, thats why i think its the caps bleeding off. I will try the pinion off test later (eating dinner right now)

[crazyjr]

I think i figured it out, the Traxxas reciever is very old design, compared to Modern designs. I tryed without a steering servo and there was still a 2 amp or so draw, i think its the traxxas reciever being inefficient in design thats causing the draw. I haven't tryed the no pinion yet, but don't think i need to.

[lutach]

I just tried the live mode on my DPR-II-150 with the VXL-3S, 11.1v lipo and it was only pulling 0.46A. It was just the controller and the battery connected.

[crazyjr]

It must be the bec feeding the reciever then, thanks. I did notice the load cut in half, from 4 amps to 2 amps without the servo, its the digital 2070

[Serum]

Something else must be wrong; it might be the eagletree as well.

If it does 4-5A on 3S, you are loosing 44.4-55.5 watts.

My guess is that the eagletree gives a bit of false information. Perhaps the noise from the receiver/esc is causing these
weird numbers.