# Brushless Amp Draw



## latemodel100 (Feb 19, 2003)

With all the talk about Amp draw during discharge of you packs at the end of the day and stuff like that I read on here, how many people have a data collection device like the Eagle Tree System that has used it with their Brushless System to find out how many amps these things pull during a race, Max and Min, and a good steady average........

I find it hard to believe that these motors being as free as they are still pulling more than 35 Amps or so........

The reason for my maddness is knowledge that we test our packs at 35 amps to see if they are still "GOOD" if they were matched at that then fine or even higher, I still dont see why you have to discharge your packs at that to tell AFTER you have them matched to find out if they are good or not.......

How many classes of Brushless motors are drawing 35 Amps that would translate in the SECs. LEFT in pack A or B equalling the same...... Why so many people focus on the large hard on your pack 35 Amp discharge curve when most of our motors are not even drawing that to compare really whats is happening....... 

Just trying to get a feel for everyones thoughts........ On after the race discharging and that comparing numbers at sucha high rate.....


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## Jamie Hanson (Dec 3, 2002)

I will be playing with that this weekend. I have tested in Stock sedan only so far and am looking forward to brushless oval.


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## swtour (Oct 8, 2001)

I've really been wanting to use my "EagleTree" Data Logger, but I've never taken the time to install it in a car.

I know when running a B/L car on a chassis dyno - it's hard to get the AMP DRAW you get/got with a Brushed Motor.


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## latemodel100 (Feb 19, 2003)

I am not looking to make it a certain Amp Draw just seeing what it naturally is, Please fill us in if either of you two use your loggers fro B/L Oval..............

THanks


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## pmsimkins (Nov 4, 2004)

I always see people say BL motors are more efficient, but in reality there really isn't much of a difference. Under low or no mechanical load a BL motor is noticeably more efficient, but under high load there really isn't much difference. Under a high load the vast majority of your loses are electrical losses in the windings, the additional friction losses of the brush on the commutator are pretty small in comparison.

Go out and run a 19T for 4 minutes and then go out and run a 10.5 for 4 minutes (maybe gear down the 10.5 a little so they are going a comparable speed) come back in and see how much time is left in your packs. There won't be much difference.

I think 35A is a very resonable estimate of our average current draw. I would say on average I come off the track after a 4 minute race with between 100-150 seconds left in my packs. Typically my packs have 380-400s of runtime at 35A. Add up the length of the race with the amount left over in the pack after the race and it is pretty comparable to the runtime the packs cycle out with at 35A.


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## latemodel100 (Feb 19, 2003)

Thanks PM thats sort of what I was looking for, just would like to see some data loggers out there report their findings, but that answered some questions also...........


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