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05-30-2006, 02:26 PM
| #1 |
| I wanna be Dave Join Date: Feb 2004 Location: on a Big Rock
Posts: 7,837
|  Technical question I have a little project I am working on with a electrical engineer who has no knowledge of anything rc. 2 questions that he asked me, and I was unsure about. "What is the current capacity of the batteries you use?" and "What is the stall current of the motors you use?" I assume on the battery question it is 7.2 on a 7.2 pack, but I have no idea about a motors stall current. Last edited by Fishmaxx; 06-02-2006 at 09:42 AM. |
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05-30-2006, 02:43 PM
| #2 |
| 2006 2.2 National Champ   Join Date: Dec 2004 Location: Big Bear Lake
Posts: 8,328
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There's some good info on motors here. http://www.rccrawler.com/forum/showt...=stall+current I think the capacity is just how big the cells are, 2400, 3000, 3300. |
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05-30-2006, 03:01 PM
| #3 |
| MODERATOR™  Join Date: Jul 2004 Location: Ohio
Posts: 18,928
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Depends exactly what battery you're asking about, but today's newer Sub Cs, like the Elite 3600 can do up to about 10C (~36 amps), and still hold near 1.2 volts per cell. If that's what he means? I don't know if I've ever seen a definate answer on when the Lathe motor stalls. I know I've read 90 amps, but I'm not too sure that's been tested. |
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05-30-2006, 05:01 PM
| #4 |
| owner, Holmes Hobbies LLC  Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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Good sub C's will handle much higher amp draws. The IB 3600's I have will discharge at 80 amps continous, and burst over 300 when they are hot. Hotliner guys like to push cells till they pop  I havent ever seen an answer on stall currents either. I need to get an ampmeter and put it to rest. I would guess 35 -45 amps for a 55t lathe motor on 6 cells. |
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05-30-2006, 05:16 PM
| #5 | |
| MODERATOR™ Join Date: Jul 2004 Location: Ohio
Posts: 18,928
| Quote:
Do it. | |
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05-30-2006, 07:19 PM
| #6 |
| 06 Super National Champ  Join Date: Jun 2004 Location: Stark Industries Bar and Grill
Posts: 11,361
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Stall current varies from one motor to the next. Same with batteries. Better batts will be capable of a higher discharge rate that cheap batts. Too many variables to give him a definitive answer. But the first question could be interpreted two different ways... Was is the current capacity? Meaning, "What is the capacity of the batteries?" OR...he could mean "What's the max discharge rate?" Both questions are pretty broad. It's like saying you're going to do a research paper on American History. I've had EE guys at NASA say that the things we're doing with RC batts aren't possible. That the charge and discharge rates are wrong, etc. Hopefully your EE guy will better understand things. |
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05-30-2006, 07:23 PM
| #7 |
| owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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I didnt believe that sub-C's would discharge at 80a continuous till I saw the flight graphs and discharge graphs from battlepacks.com. I think the only reason they never got more than a few minutes of that amperage is because the plane will dissapear into the sky! Edit: just realized I sold all my lathe motors this weekend, and they shipped out today. Oh well, no testy for me  Last edited by JohnRobHolmes; 05-30-2006 at 07:27 PM. |
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05-30-2006, 07:33 PM
| #8 |
| MODERATOR™ Join Date: Jul 2004 Location: Ohio
Posts: 18,928
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No testy for you...  |
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05-30-2006, 07:34 PM
| #9 |
| 06 Super National Champ Join Date: Jun 2004 Location: Stark Industries Bar and Grill
Posts: 11,361
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Crap. Let me go stall a damn lathe motor... Be back in a few. Ok, just connected a new Integy 55 turn lathe motor to an E-flite Power Meter. I used a 6 cell pack that I use in my Roto-Start. I charged it yesterday. Pack showed 7.8V on the meter. With the motor stalled the meter showed 18.4A Last edited by JasonInAugusta; 05-30-2006 at 08:13 PM. |
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05-30-2006, 09:34 PM
| #10 |
| I wanna be Dave Join Date: Feb 2004 Location: on a Big Rock
Posts: 7,837
| Thanks guys, and at least now I don't think I asked a stupid question. I don't think he needs exact #'s .....just typical to what we might see in crawling. |
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05-30-2006, 09:48 PM
| #11 | ||
| MODERATOR™ Join Date: Jul 2004 Location: Ohio
Posts: 18,928
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Funny. If ya read it on the internet it must be true. Quote:
Quote:
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05-30-2006, 09:58 PM
| #12 |
| 06 Super National Champ Join Date: Jun 2004 Location: Stark Industries Bar and Grill
Posts: 11,361
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90A damn!  BTW, this motor is pulling .6A at no load, which is consistent with what jam1sstang got from his 55 turn on his Indi dyno. |
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05-30-2006, 10:02 PM
| #13 |
| MODERATOR™ Join Date: Jul 2004 Location: Ohio
Posts: 18,928
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Hey! I got an idea. Test some more motors!
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05-30-2006, 10:05 PM
| #14 |
| 06 Super National Champ Join Date: Jun 2004 Location: Stark Industries Bar and Grill
Posts: 11,361
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You ship them yet? |
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05-30-2006, 10:21 PM
| #15 |
| MODERATOR™ Join Date: Jul 2004 Location: Ohio
Posts: 18,928
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coughbrushless
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05-30-2006, 10:28 PM
| #16 | |
| 2006 2.2 National Champ Join Date: Dec 2004 Location: Big Bear Lake
Posts: 8,328
| Quote:
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05-30-2006, 10:31 PM
| #17 |
| I wanna be Dave  Join Date: Dec 2005 Location: Happiness is a warm AK.
Posts: 12,563
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Now that would be some interesting info!  |
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05-30-2006, 10:41 PM
| #18 |
| 06 Super National Champ Join Date: Jun 2004 Location: Stark Industries Bar and Grill
Posts: 11,361
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To do the same test I'd have to make the measurement on the battery side of the controller instead of between the controller/ESC...unless I used an AC ammeter. I'm thinking I'll use my 40A E-flite ESC for that test. Or maybe that 120A Mtroniks unit that's laying here. Last edited by JasonInAugusta; 05-30-2006 at 10:43 PM. |
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05-30-2006, 10:51 PM
| #19 |
| RCC Addict Join Date: Mar 2005 Location: Saginaw
Posts: 1,721
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Do it!  Gotta love numbers and technical specs most people could care less about  Last edited by Mad Scientist; 05-30-2006 at 10:54 PM. |
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05-30-2006, 11:01 PM
| #20 |
| owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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Different esc's will get different stall amperage I bet. The mamba would be just fine too. dont be a wimp
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Linear Mode
