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Old Aug 19, 2003, 07:00 PM
Registered User
Wisconsin
Joined Aug 2002
19 Posts
newbee question speed 400 motors

I am breaking into electric flight and have been cruising through the catalogs and came across a quandry many times. I see many kits including 6V speed 400 motors and 7cell battery packs. Correct me if I am wrong but doesn't 7 cells put out 8.4V? Is this right? If so, what is a 6V speed 400 rated to run at?
Please elaborate.
Confused
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Old Aug 19, 2003, 10:34 PM
Motors beat engines!
Milwaukee Wisconsin, United States
Joined Feb 2001
4,564 Posts
The motor voltage ratings are nominal, more reflecting the rpm/volt rating than anything else.

You can run a 6V motor on 12V if you want to, as long as gearing and prop choice keep amps down to around 10 or so.

Dean in Milwaukee
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Old Aug 20, 2003, 06:11 AM
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ChrisP's Avatar
Weilbach, Germany
Joined May 2001
2,467 Posts
This may interest you. I did a teardown on a 400 after 530 flights on 8 cell packs (which means 8.8 volts under running conditions).
http://www.rcgroups.com/forums/showt...light=teardown

As Dean said, the voltage stated is nominal only. Nobody runs 6v 400's on only 5 cells.
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Old Aug 20, 2003, 06:56 AM
Registered User
Wisconsin
Joined Aug 2002
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all motors or just speed 400s

Does that rule apply to all motors or just speed 400's? If not, how do I know which ones?
THanks
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Old Aug 20, 2003, 07:59 AM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,266 Posts
We're equal opportunity motor abusers. Run a 6v motor on eight cells, a 7.2v motor on ten, etc. The killer of motors is amperage and that's what you need to keep an eye on.

mw
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Old Aug 23, 2003, 08:32 AM
Woohoohoohoohoo! AGAIN!!
Randori's Avatar
Manly Vale, Australia
Joined Aug 2003
119 Posts
sweet, finally I think I may get the explanation I need. Amps. What relationship do amps have from the battery to the speed controller to the motor?
Is it possible to burn out a speed controller because it can't handle the amps produced by the battery?
In the same vein is it possible to burn out a speed controller because it can't handle the amps that the motor is capable of using?

Thanks,
R.
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Old Aug 23, 2003, 11:20 AM
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Chattanooga, Tennessee, United States
Joined May 2003
27,197 Posts
Frying ESC's

G'day mate!

Think of your battery as a passive holding tank for electrons. It doesn't actually matter what capacity battery you use. It's what you ask it to produce that matters. It will only supply current [amps] through the ESC when the motor asks it to. So, if you load your motor [and/or throttle up too much] so that it draws more amps from the battery than the ESC can deal with [for example, drawing 15amps through a 5amp ESC], then you may find expensive smoke coming from the ESC. There are also limitations to cell count [i.e. voltage] for ESC's too, so don't use a 10 cell pack on an ESC rated for only 6.

Cheers, Phil

P.S. I trust the All Blacks are a match for the Wallabies this season, but I assume, in the absence of any news over here that your cricketers were probably for too good for the NZers as usual last summer!
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