First Build - Power System Help (and introduction!)

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IgnorantCarb0n

New Member
Hi there, introducing myself! and embarking on my first build and have bought some motors that were cheap, http://www.giantshark.co.uk/product/171775/c3536-09-kv910
so i decided to build around these, i bought some 70amp ESCs to go with them: http://www.hobbyking.com/hobbyking/store/__7340__hobbyking_ss_series_60_70a_esc.html

....I then found the calculator :http://www.ecalc.ch/xcoptercalc.htm and have been playing around with it to find a suitable battery/prop combination. But i cant seem to find any combinations that give me flight times of more than 10 minutes of hover and much less of normal flight.

anyway onto the question(s). am i approaching this in the right way? is the calculator an accurate model? what flight times should i be reasonably expecting, considering that my build will be aimed toward efficiency and flight time rather than maneuverability? Basically any advice on battery/motor/prop combos for efficient flight would be most welcome.

Thanks in advanced!
 
I'm somewhat confused as to why that motor page is suggesting 70A ESC's. The max running amps on those motors is around 37 - which means you'd be good with a 40A ESC. Any 40A ESC can run 40A continuous and will burst to 55 or more for up to 10 seconds. If your max amps on your motor is 37, you'll probably never draw near that as long as you don't run more than 4S batteries and use the right props.

ecalc is fairly accurate, but the only way to get good potential flight time data is to copy someone else's setup or use ecalc to come up with good designs, then test and tweak. Long flight times are definitely possible, but then again it depends on how big your copter is going to be and how much payload you want to carry (cameras, FPV equipment, etc.). If you're just looking for max flight time, build one of these =)

http://www.diydrones.com/profiles/blogs/my-97minute-06second-record-quadcopter-flight
 
hey thanks for your reply, i like the look of that setup, i was aiming for something similar (large props lightweight materials) but maybe with more potential payload. I guess i went in the wrong direction buying motors first? I am only just beginning to understand the ratings of rc equipment like kv etc. for example am i right in saying kv doesnt really fully represent the motors power, but its max current rating? when selecting batteries does the C rating relating directly to the max current draw from the battery? and S the number of cells relates to voltage suppplied?

thanks again for your help!

EDIT: PS how can i find the number of poles of a motor?
 
kv is basically the number of revolutions per minute per volt applied to the motor. A 910kv motor will theoretically spin 910x per minute for each volt applied to it. kv is somewhat confusing though. As a general rule:

Lower kv (1,000 and below) - You'd run bigger props and more cells in your battery (4S and above). This setup will give you more torque, thrust, and ability to lift. Also, bigger props at lower kv will be more efficient. This setup is more stable, but less agile. I've flown both styles and I think this is much easier to fly because it gives you some time to think.

Higher kv (Above 1,000) - You'd run smaller props and can run 3S batteries. You'll get more speed and agility here. You can still run a GoPro and FPV and carry a decent payload though, even with 3S batteries and 1200kv motors. It will just be a bit less stable in the wind - but more sporty and responsive.

For your second and third questions, this should be pretty helpful:

http://multicopter.forestblue.nl/lipo_need_calculator.html

S is number of cells and different types of batteries gives slightly different voltage per cell. Lipo batteries is about 3.7 volts per cell. Don't ask me why cell is represented as "S"! C is simply the max continuous discharge rate of your battery. Some batteries also give you data on burstable discharge rates. The C rating will give you the max amps you can continuously draw, but you have to do some calculation (see the link above).

The number of poles in a motor is sometimes listed in the motor specs... or usually. Not always though. If it's not, you'd have to ask the retailer or manufacturer.
 
Hi mate a friend of mine has just finished his and has a 19 min flight time thats good , as mine is for speed and acro will only fly 5 mins my boys light weight one does 10-15 mins , he is a link for is video
 
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