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Old Jan 07, 2007, 07:13 PM
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Problem with outrunner

I have a Slo-Stick that I put a Tower Pro bm2408-21 motot on with a 20 A brushless esc. I am using a GWS 8 cell 750 mah Nimh battery, which has been used about 6 times. I have been using the reccomended 8x4 prop. The problem I'm having is that I only get about a minute and a half or so and the the low voltage cutout kicks in. I can reset it by going back to 0 throttle and then it will work for a little bit and cut out again. I'm thinking that maybe these motors draw the Nimh batts. down at full throttle which causes the cut out. Do I have to use Lipos?
Bill
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Old Jan 07, 2007, 07:20 PM
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Is it possible that your low voltage cutoff is not set appropriately for this battery?
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Old Jan 07, 2007, 08:08 PM
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It is a programable ESC and I did double check it an it tis set for Nimh.
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Old Jan 07, 2007, 08:18 PM
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you may be drawing to many amps from the cells. They may not be able to take the probably 10 or 11 amps your drawing, causing their voltage to drop, causing your ESC to cut out.


Try some nicer cells...even a 15c pack at 750mah is good for 11 amps. And should do the trick.
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Old Jan 07, 2007, 08:30 PM
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You may have a bad cell in the pack or could the cells in the pack be out of balance? Try to discharge the pack with a watt meter to to see what the true capacity is. A bad cell can lower the capacity of the pack, causing an early drop in the voltage.



Jerry
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Old Jan 07, 2007, 08:56 PM
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I agree with anatoly... your esc is set for the wrong low voltage cutoff.
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Old Jan 07, 2007, 10:14 PM
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I tend to think that the pack is O.K. becauese it worked with a regular brushed motor. I also tried a 7 cell pack with the same if not worse results. The only setting I have on the esc for the voltage cutout is high, low and medium. i guess I will play with those settings some more when the wind dies down. Thanks for all the advise!
Bill
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Old Jan 07, 2007, 11:29 PM
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You need to find out what "high, medium, and low" mean as far as voltage.

John
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Old Jan 08, 2007, 11:23 AM
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The levels are percentages of the total pack volatage Ex: high=70%...A9.6 volt pack would then cutout at 6.7 v I think the low was at 60% which would give the greatest amount of voltage before cutout but it didn't make too much diff. It seems like most people are using Lipos in conjuntion with outrunners, brushless etc.. which makes sense if you are going to upgrade. But I get less performance as opposed to a stock 350.
Bill
.
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Old Jan 08, 2007, 11:31 AM
Master of 1 point landing
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Quote:
Originally Posted by coyote223
I have a Slo-Stick that I put a Tower Pro bm2408-21 motot on with a 20 A brushless esc. I am using a GWS 8 cell 750 mah Nimh battery, which has been used about 6 times. I have been using the reccomended 8x4 prop. The problem I'm having is that I only get about a minute and a half or so and the the low voltage cutout kicks in. I can reset it by going back to 0 throttle and then it will work for a little bit and cut out again. I'm thinking that maybe these motors draw the Nimh batts. down at full throttle which causes the cut out. Do I have to use Lipos?
Bill
you have your esc set for LIPO cut off?
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Old Jan 08, 2007, 01:38 PM
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Nope, I checked and its set for Nimh
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Old Jan 08, 2007, 02:52 PM
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Quote:
Originally Posted by coyote223
Nope, I checked and its set for Nimh
We've done everything except look at the actual equipment you're using.

Find the specs for the motor you have and post them here. Also find the specs or the detail sheet for the esc you have, including the manufacturer of it.

Lots of times, people post their motor like "I have a Flidgett Express 12045GT", and of course, that tells us nothing about it's recommended continuous amp draw, or it's burst rating, or anything else.

Chuck
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Old Jan 08, 2007, 03:08 PM
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Here is a link to what I have.

http://www.himodel.com/electric/Towe..._ESC_Combo.php
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Old Jan 08, 2007, 03:36 PM
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Quote:
Originally Posted by coyote223
This is certainly strange. Outrunners are usually sold as having so many rpm's per volt (kV). Yet yours isn't listed that way.

What is listed however, is a chart showing what you can expect, current and voltage wise when you are running the motor through a gearbox ratio of 1:5.3

If this motor is indeed supposed to be geared, and you are running it direct drive, I'm amazed you haven't burned it completely out, along with your esc and battery.

Something is strange indeed here!

Chuck
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Old Jan 08, 2007, 03:54 PM
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Here is a better link. That must be a typo on that other one because it sure isn't direct drive also those props seem too large.

http://rds.yahoo.com/_ylt=A0geuuVuvK...pe2408-21.html
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