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Author Topic: Batteries for Brushless  (Read 1274 times)

gingyer

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Batteries for Brushless
« on: September 16, 2009, 10:44:19 PM »

I have been reading up in brushless motors
Can anyone tell me is there a certain type of battery I need to
use with the Brushless motors or could I use any battery
like a 6v 10Ah SLA?

Thanks
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Proteus

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Re: Batteries for Brushless
« Reply #1 on: September 16, 2009, 10:50:12 PM »

It's OK as long as you don't want to flatten it to quick, they wont happily discharge fast


Proteus
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gingyer

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Re: Batteries for Brushless
« Reply #2 on: September 19, 2009, 11:03:23 PM »

ok thanks :-))
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dodgy geezer

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Re: Batteries for Brushless
« Reply #3 on: September 28, 2009, 03:13:17 PM »

You might be interested in some early data from my bathtub?

I have got a test boat together - see it at http://modelboats.hobby-site.com/RAFPics1.html .

I have just given it a first run with a brushless. The figures are:

9v dry Batteries  (9.33v off-load)  -  Fine pitch propeller thrust - 66gm
                                                Coarse pitch propeller thrust - 125gm

2 cell lipo battery 20C (7.92v off-load)   Fine pitch propeller thrust - 427gm
                                                Coarse pitch propeller thrust - 395gm


I interpret this to mean that the brushless motor can soak up a lot of energy if it's available. With the dry batteries the motor was limited by the amps the dry battery could put out, which was low (AAs). So the prop could only spin up to a certain fixed speed, and at one speed, a coarse pitch prop will provide more thrust than a fine one.

With the Lipo, the motor could have as much energy as it wanted, and it was limited by the drag from the propeller. The high drag of the coarse prop kept the speed down, and the extra speed the fine prop provided actually produced a noticible increase in thrust.

Of course, someone else may know different.....
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