R/C Tech Forums - View Single Post - How much amps (continuous & peak) will a brushless system draw?
Old 11-23-2007, 05:49 PM
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Turbo Joe
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Ohh..I see...I ask a question...get an answer...ask another question about the results and say it doesn't seem right to me, but that I may well be wrong -- and that's "flaming".

Glad you cleared that up for me Mr. Flack. And by the way, where did I tell anyone I "...didn't care what they thought"?

I know that it's possible for people to make some pretty egregious calculation errors on this stuff. I think (actually, I know...) even Mr. Stranahan has done so before on this very board, nobody else even noticed...LOL...heaven forbid anyone say anything. You know how dangerous questions are...

If you have a valid answer to a question or an accurate model, it will stand up to reasoned scrutiny or hold up when you substitute different values. But alas, it's all about my perceived attitude, rather than any of those "facts" you guys say you want.

I think it would be much more accurate to do some sort of "measurement" if you really wanted good information, rather than trying to guess at the color of the carpet from outside the house. Whether that's feasible or not is another question altogether, but you would actually see what's really happening, rather than just guessing at it by how much gas is left in the tank. You can guess at horsepower by the fuel consumed over a certain period of time, but lacking information as to the air/fuel ratio, it's a junk guess. That's an imperfect analogy, but I don't think it's too far off.

Look...as I've said several times before in this thread...I'm not convinced that I'm right. I'm just not convinced that you guys are, either.

Drew == you're calculating the amp draw of a 3.5 from a rating that Novak posted on their website. A rating that I bet you have no idea how they arrived at. You don't know the conditions. It says "average over 6 minutes." 6 minutes of what? There's a big problem when you use imperfect/incomplete information, boil it down and use it to draw conclusions.

John == I'm not saying your 45 amp number is "wrong". I'm saying that it should (and does to me) sound suspicious when you happen to arrive at a 45 amp number from what you say is a motor that draws 90 amps peak on a large track. You just couldn't. Maybe it's just a deal where my educational (a lot of number-crunching in my degree field) and racing background makes me look for stuff like that and give it a second look.

Maybe (probably) the true peaks are FAR higher than what you think...if that was the case, then 45A doesn't sound unreasonable. The GTB is rated at 540 Amps for some reason, right? The XBR is rated for 120A and that's not even a 7.5.

That...and if I'm understanding you correctly...you're measuring your draw relative to a discharge you ran one time, presumably when the battery was new. Why not just measure what you have to put back in and base your numbers off that? I would think that would introduce fewer errors into your numbers due to pack degradation and loss of capacity. This deal is already like a horse being nibbled to death by mice. The more additive errors you introduce, the farther from the real number you're going to be.

Last edited by Turbo Joe; 11-23-2007 at 07:47 PM.
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