Electric Flight

Hi,
I am a newbie in the world of electrics, having flown glo for many years.
I have a few questions:
1) My biggest concern is flight times - what sort of average times can I
expect from a mid size - say 400 motor aerobat?
2) Where can I get Li-ion's from in UK - and what discharge rates can I expect?
3) How can I calculate the amp draw from individual motors - I am unsure what size to go for?
4) Although I understand the need to match the battery voltage to the motor voltage, is there any restriction on what mah (other than weight) that I can use with particular motors?
Sorry for the ignorance, but it seems quite appealing if I can begin to understand some of the maths.
Ta,
Paul
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Simple! Just go to http://www.ezone.com & ask away!

motor
can
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nope! go to http://www.ezonemag.com / and click on discussion groups

years.
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Paul Lamb wrote:

3-5 minutes Nicad, 5-10 minutes NiMh, 10-40 minutes Lithium Polymer. Those are VERY approximate sort of figures assuming many thiungs that may not be true.

I hope you mean Lithium polymer.
In the UK, Irvine are distrubuting Kokam and one other brand.
One guy is importing E-tech, and a few others are bringing in Kokams.
I get E0techs from Japan www.aircraft-world.com and some really good cells (Irate) from www.cheapbatterypacks.com. They have both proved reliable suppliers.
Thunderpower cells are available fom West London models.

Ask on the E-zone. Generally manufacturers are ratuing their cells by the ration of current drawn to teh one hour capacity. i.e. a '5C' cell of 1200 mA/h capacity is rated at 6A drain for sfaety. E-tech are probably a 6C cell, Irate 10-12C, Thunderpower between. Kokam 7-10C.
www.motocalc.com is a free trial program that will save you more money than it costs.
www.ezonemag.com is the best electyric flight resource center on teh net. Free.

There is no particular need to match teh voltage to what it says on te motor can.
For example, I ran some tests yesteday on a 6v motor drivibng it from 3 cell LIPO - about 12V. It performed far better than it does at its usal 6-9v.
You can use whatever mA/h you like, provided it can deliver the peak currents without overhgeating and exploding. Current rates of at best aroudn 10C means in general you will always get at least 6 minutes flat out with a LIPO pack. If you take 6C as the maxium rate yiu really ant ti use on a continuous nbasis, you will get a minimum of 10 minutes full throttle. In practice unless plylon racing, you use the throttle, and will get far more.

Hit the ezone - I am around there, and would prefer to pass on teh little that I know there. Its a better forum than here.

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Trial Motocalc? Sweet. Gotta go.... Thanks for the link, i thought it was expensive so i never bothered to look.

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wrote:

Not as powerful and complete as Motocalc, but for basic calculations, my web based Eflight calculator will do the job:
http://www.csd.net/~cgadd/eflight/calcs_motortest.htm
Chuck Gadd http://www.csd.net/~cgadd/aqua
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Howdy. Mee to, i just have a couple months head start...

Depends on the battery you can afford. Maybe 6minutes minimum to 30ish max depending on throttle usage, prop, plane, and what battery you get.

Dunno. Been to the UK once. When i was 14. Lovely place, lousy weather. Discaharge rates vary dramatically depending on battery. Best bet is to find out what motor the plane your interested has, Then what prop works best, then what amp draw the combo produces, then select a big enough ESC, then select a pack big enough to deliver the amps. A 1500 kokam can (IIRC) deliver 12 amps. Try not to work in circles. Select a few planes, write them down, and work from there. Research. Google. Not hard, but time consuming. Always get stuff that can handle more than what you need. If your desired setup will call for 12 amps, buy a 20amp esc. That gives you playroom for different props/motors/gears.

Motor size is usually based on the plane its flying. Make a short-list of planes and compare. Many sellers show you the recommended motor/esc/battery on their site. My GWS slowstick - no aerobat by any means - draws maybe 7 amps with the GWS-recommended prop and gearing. Its well-matched to an 8.4 900mah nimh or a 1200+ lipo. Otherwise, ask somebody with the Motocalc Program to check it for you. There are several guys on rcgroups.com who are really helpful at this.

Voltage? some motors tend to burn out rapidly on 9.6v & up, but usually an 8.4v will be fine with plenty of power. With amps, your only restricted by what your pack can deliver. I got a cheapie 600nicad with my plane...at 7amp draw, the battery cant supply it fast enough so the voltage dips and trips the Low Voltage Cutoff feature on my esc. Generally, bigger or better quality cells can pump out more amps. I recommend Nimh because its lighter, so you can go bigger for more runtime and current capability.

Just wait till you start looking into brushless...yeeesh. Best of luck, mike

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