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Old Oct 14, 2012, 05:08 PM
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how to pick a lipo

Hi im new to this and im trying to find a lipo batt. for my brushless motor
Motor specks are 5-13V 100w 3S 1600KV max continuous current 8A and peak is 10A

Thanks
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Old Oct 14, 2012, 06:05 PM
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Sverige, Värmlands Län, Filipstad
Joined Jan 2009
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Link to motor?

What plane do you intend to use it in?

One usually say LiPo have 3.7 volt per cell so a 3 cell has 11.1 volt (but a fully charged LiPo cell has 4.20 volt).

You can use up to 3 cell LiPo with the specification You have told so far.
How many milliamerehour (mAh) the LiPo battery should have in your case depend how long you want to fly and how heavy battery your plane may be able to carry.
How many amp your motor will draw out of the battery depends on propeller You use.
ecalc hompepage is a good start for that but maybe little early for You now since You are new to this.
You select a speed controler (ESC) that can handle the amp (and some more for safety margin) your setup will draw.
Some speedcontrolers has a BEC so You can connect it to receiver to supply servo and receiver with power.

/Bo
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Last edited by bossee; Oct 15, 2012 at 01:44 AM.
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Old Oct 14, 2012, 07:40 PM
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its came with a esc to

http://www.hobbypartz.com/98p-mars-b...12a-combo.html

Im putting it on a trainer plane made of fff foam using a 8x3.8 prop
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Old Oct 14, 2012, 07:56 PM
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USA, MO, Ballwin
Joined Mar 2010
634 Posts
I would suggest a 1300-2200mah battery, 3s of course. My thoughts are that an 1800mah battery would give you good flight time and be a bit lighter than the 2200mah battery making for easier landing weight.
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Old Oct 14, 2012, 08:48 PM
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should it be a 25c batt or more, less?
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Old Oct 14, 2012, 11:14 PM
222 km/hr Parkjet flyer
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Quote:
Originally Posted by Jstryin2fly View Post
should it be a 25c batt or more, less?
It all depends on amps demand of your motor / prop combination.

It;'s nice if you can use a 20C ... as they are cheap and cheerful prices. Also they are lighter and you can go for a higher mAh capacity for increased run-time.

But generally you would want to go for higher C rating and then battery is suitable for other models as well ... it allows a greater amp demand on it.

When looking at spec's of motors - remember that amps they quote are usually way lower than you experience in real life. Second that the volts range is as designed - but often you can go 1x S rating higher if you are careful with throttle.

To choose your battery :

a) you need to know what cell size ( S rating ... in your case it's pretty obvious you'll go 3S .. 11.1V)
b) you need to know the max amp draw ... with the prop and motor combo. A Wattmeter is called for there .. you could ask around and see if anyone has similar set-up and what size LiPo and ESC they are using.
c) you need to know battery compartment size for maximum pack size possible.
d) you need to know weight of packs.

Most LiPo adverts will give sizes and weights ... so that's sorted. The question remains about amps ... which decides run-time and also what ESC to use ...

Also note that you can go up in prop size and reduce S rating accordingly ... it is common for a model to perform better with a larger prop on 2S pack than a smaller prop on 3S ... using a 2S can also give you a lot better run-time and much bigger capacity pack for same weight etc.

Nigel
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Old Oct 17, 2012, 09:11 PM
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Thanks for all the help
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