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sizing batteries for quad copters

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rickeis View Drop Down
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  Quote rickeis Quote  Post ReplyReply Direct Link To This Post Topic: sizing batteries for quad copters
    Posted: 06/Mar/2012 at 1:50pm


I am building my first quad copter and already have the 4 motors, propellers and speed controls.

I would like to see the calculations to find an appropriate battery.

These are the motors I have

http://www.hobbyking.com/hobbyking/store/__5423__FC_28_12_Brushless_Outrunner_1534kv.html

These are the speed controls

http://www.hobbyking.com/hobbyking/store/__11615__Turnigy_AE_20A_Brushless_ESC.html

The 4 props are 7 X 3.5 two are reverse or counter rotating.

Thank you so much for your help
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rickeis View Drop Down
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  Quote rickeis Quote  Post ReplyReply Direct Link To This Post Posted: 06/Mar/2012 at 3:09pm
Should I get 4 batteries.....One for each motor?
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  Quote engineersupreme Quote  Post ReplyReply Direct Link To This Post Posted: 06/Mar/2012 at 4:27pm
No
One battery is all that is used.
You need to get a power supply board that connects all 4 esc to the battery.
In other threads in the multirotor section are pictures of boards made by other members.
I myself made one then decided to get the dedicated items, NOT avaliable from HK yet. fleabay has them in multiple shops they are about 3 to 7 dollars US, they make everything neater
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  Quote rickeis Quote  Post ReplyReply Direct Link To This Post Posted: 06/Mar/2012 at 10:31pm
Thanks engineer supreme - So how does one calculate the size of battery and if it should be 20C or whatever?
Thanks again,
Rick
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  Quote rickeis Quote  Post ReplyReply Direct Link To This Post Posted: 07/Mar/2012 at 3:36am
I read a lot about folks burning up speed controls etc. Can you suggest a battery to get me started?

I was looking at purchasing a few ZIPPY Flightmax 1000mAh 3S1P 15C for my set motors and speed controls decribed above.

15C would give me 15 amps with this battery (if I am understanding things correctly), and it would have a 20A to 25A burst capability.

Now the speed control says it could handle 25A for 10 seconds....so it appears to be a good match...yes?

Where it gets confusing to me is when we have 4 motors? It seems this battery would run out very quick. But if I go to a 2000mAh, a 15C battery would have the potential of 30 amps or more ....again assuming I'm understanding things correctly. And it appears 30 amps could blow out one of the speed controls ??

So, what am I missing..or do I have it right?

Thanks again,

Rick


Thanks

Rick
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  Quote engineersupreme Quote  Post ReplyReply Direct Link To This Post Posted: 07/Mar/2012 at 5:52pm
Im not into the calculations, however the Hobbyking Super Mini Quadcopter Frame with Motors (445mm) has a recommended package as below

ESC: 4 x 10A
Battery: 1000mAh~1300mAh 7.4v 2S

for running the four motors

Motor Specs:
Rpm/V: 2800kv
Voltage: 7.4v (2s)
ESC: 10A
Weight: 16.9g
Suggested Prop: 6x3"

Motor Test Data:
6030 7.0V 6.9A 48.3W 12660RPM 226G
6030 7.8V 7.5A 58.5W 13140RPM 252G
6030 8.4V 7.9A 66.3W 13320RPM 262G

There are many sites with untold data already worked out for them

Im still trying to work out the multirotor stuff

having more fun with cheap flybarless gear refitting my 450's and 500's
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  Quote dsiee Quote  Post ReplyReply Direct Link To This Post Posted: 27/Mar/2012 at 10:18am
amp draw is more about potential, just because the battery can deliver 20A doesn't mean it will.
so if you have 4 motors drawing 16A (this is for a DT700) thats a total of 4*16 so 64A so a 2200mah battery must be 2200*x=65000mAh thus must be ~30C.
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  Quote rickeis Quote  Post ReplyReply Direct Link To This Post Posted: 27/Mar/2012 at 1:43pm
dsiee,
Thank you.
Excellent...this is exactly what I was looking for. So assuming all four motors were running on 16 amps and assuming we are talking about a 3 cell battery......what do the calcs look like to estimate the running time of this battery you use in the example
Thanks again,
Rick
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  Quote IslandScott Quote  Post ReplyReply Direct Link To This Post Posted: 19/Apr/2012 at 2:59am
I run the 1200 KV version of your motors. My quad weighs 1 KG. With 9x5 props I pull around 18 amps at hover and 44 amps at full throttle. You are using a smaller prop, but higher KV motor, so I suspect you will see a similar current draw.

I like to oversize my C ratings a little so I'm not stressing the battery.I mostly use 2200mah 25C (50C burst) batteries (capable of 55 amps constant). This gives me 2.2 / 18 = .122 hours = ~ 7.3 minutes.
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