hi..

i wanna build a quadrotor...i dont know which battery would suit best for driving the quadrotor....with four 18A ESC....i want to fly the quadrotor for around a max of 15 minutes...can any specify which battery would suit best...i mean the specification of the battery..

will i have to use four battery for each of four esc...or only one battery is enough..

Its better to use 1 battery cause if you use 4 batteries and say you turn left more than right then you'll use up the right battery more and it will run out earlier than than the left battery....

Ok if ur using 18 A esc, then you need 18*4 = 72 amps.. thats the highest amps you'll be drawing from the battery... now you see the C rating of the battery...multiply the C rating with the ampere hours rating of the battery and that is the maximum amps you can draw from the battery so if you take a 15C battery rated at 5000mah you can draw 15*5 = 75 amps from the battery.... so its good...

To calculate what maH battery you need, you calculate the average amps you'll be drawing from the battery, that you'll have to experiment around with... just see how many amps your drawing from the battery when your hovering, say its 40 amps, so you need atleast a (40*15)/60 = 10 aH battery or 10,000maH battery... Now note your average current drawn will be a little more than 40 amps because your always not on hover mode....

What I did was to plan for 1 or 2 batteries. 30C, 40C and even higher C rating batteries are common now, so one battery should be able to do it (not sure about 15 minutes, that would require quite a bit of mAH, at the risk of added weight).  Plus, hopefully you never need full throttle power (assuming your prop selection etc is good), so one battery should do (this is what I am seeing in practice, although my quad is still not stable).  If the time/need comes, be prepared to use two batteries.  I have rigged up deans connector setups for either one or two batteries.

Hey Anwar do you mean using 2 batteries separately or 2 in parallel?

Just drive two ESCs with one battery, and the other two with another battery.

hey ....


how long will the battery last..???if i use 5000mah 15c battery..

will i use 2s or 3s battery./...??

hey...


what do u propose me to  use.......1 5000mah 15c 3s battery...or 2 2500mah 15c 3s battery..??
which one is better..??in case of full throttle which 1 is better..??

Please read above responses carefully.  There are never really exact answers to many questions, you have to experiment. 

5000mAH would be quite heavy.  If it were me, I would plan for two 5 to 7 minute flights using one 2500mAH battery at a time, instead of one 15 minute flight using a 5000mAH battery.  BTW, I do NOT imply that a 2500mAH battery will yield exactly 5 to 7 minutes flight (those were just sample numbers), the actual flight time depends on many factors, a major ones being the AUW of your craft, your prop selection etc.

hey....

in your previous thread u posted that i rather use 2 2500mah one at a time...

will a single 2500mah 15c be sufficient to power 4 18A esc..??i dont think so...??

Like I said, it is all about experimentation.  Calculations work as guidelines, there are practical considerations that come into play.

I am playing with 2 1000mAH 30C batteries and 2 2200mAH 40C batteries (and couple of prop sizes), and for my stricken quad to lift off and hover, I need less than 50% throttle.  The idea to experiment with different weights, at least that is what I was doing. 

Secondly, I never mentioned anything about 2500mAH 15C being sufficient.  One cannot categorically write them off either... if your craft setup is good (light enough with right prop etc)  you don't need high throttle, so even a 15c battery can work. One thing is for sure, you cannot go wrong with higher C batteries (which are very common now) !

The key issue is that everyone's aircraft is different from each other, and there is no "measured quantity" that fits every case.  Over engineering a little bit seems to be the best route.  Do a bit of research on the weights of batteries of various mAH, and see what it adds to the AUW of the quad.  If you have read through the electrical power threads here, you will realize that the first thing people ask for during power system selection (motor, ESC, prop, battery), is the weight of your aircraft, and you have not posted any such detail so far.  Having said that, even if you posted the weight, it is not clear how the thrust calculations of a single motor setup is translated to a quad setup (do you need x/4 thrust or x/3 thrust or x/2 thrust for each motor, as compared to a single motor setup?).

If you are looking for someone to tell you to go get exact specifications of a battery for YOUR quadrotor, I think you will be disappointed   There are enough variables and lack of personal experience here (from what I have seen so far) for someone to be that precise.

how long did your flight last..

My quad is not still stable enough for sustained flights, I am waiting for additional equipment.  From my secured tests, it should hover for about 8 minutes with a 2200mAH battery, possibly more. I will post exact numbers once I get the setup fully working.

i am thinking of using the 18A esc and a brushless motor that has a specification of giving a thrust of around 700gm....the max weight of my quad would be around 1.3 kg including battery...
the prop i intend to use is the 3 blade prop from hk...both counter and normal prop....
http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=5250

i intend to use this motor
http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=8621&Product_Name=2210N_1000Kv_Brushless_motor_for_AXN_Floater-Jet_


what do u mean by x/2 x/3 thrust...?

Quote from: d33ptam on June 03, 2010, 02:48:20 PM
what do u mean by x/2 x/3 thrust...?

So your whole craft has a weight of 1.3kg.  Assume that you found a single motor/prop combo with 1.5kg thrust.  Allowing for some inefficiencies, this would allow you to lift the 1.3kg using the thrust of a single motor.  Now consider the case where you have 4 motors.  Since you have 4x the thrust now, can you get away with each motor having only 400gms of thrust (roughly x/4) ?  Or does each motor need to have 500gms of thrust (x/3) ? 

In short, I am not sure (in real life), what is the thrust requirement for a quad when 4 motors are working together.  In theory, you will need only 1/4th the thrust of the single motor, but in practice, it may be more.

kk

would u mind seeing the motor that i selected is right for my quad...??
and the prop selction also..

Here are some things I learnt about motor selection for quads (mostly from rcgroups.com).

1.  3 blade props are not really recommended, as they are less efficient.  I did not find a good source for counter rotating props, so went with 3 bladed ones from HC.  They work, but performance will be better with 2 bladed ones.

2.  Regarding the motor, you want to keep the KV low (1000 or less). 

3.  You need enough combined thrust from all motors working together to hover the quad.

4.  Given a choice, smaller props of slightly higher pitch were recommended. 

In your case, you are looking at 700gms of thrust advertised on the HK site, but that is using a 2 blade prop.  With a 3 blade prop, you may not get that much thrust.  I would put the actual thrust of your motor + 3 blade prop at less than 700g, and for the sake of calculation, we can assume something like 500gms.  So you should still be OK when 4 of them work together, assuming the AUW of the quad is no more than the current weight of 1.3kg. 

Worst case, you may have to shed some weight, probably by using a lower mAH battery.  I would also consider upgrading the motor a bit, so as to swing a 3 bladed 9x5 prop.

Let me be very clear that these is what I *expect* to happen.  I cannot be sure until I do more tests on my setup.

A single 2500 mah 15 C battery will not be enough to power 4 esc's..... whilst a 2500mah 30C battery will be good enough.... you see the the C rating multiplied by the mah rating will give us a measure of the maximum current that can be drawn from the battery.....the mah rating gives us a measure of how long the battery can run....
Anwar I think 1 5000mah would be lighter than 2 2500 mah as an example http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6501&Product_Name=ZIPPY_Flightmax_5000mAh_3S1P_15C this is a 500 mah battery weighing 364g

while this battery http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6518&Product_Name=ZIPPY_Flightmax_2200mAh_3S1P_15C is only 220mah and weighs 170g so even 2200x2 = only 4400 mah with a weight of 340g so the 5000mah battery is a better choice... since your getting 600 mah more with gaining only 24g of weight..

Now balancing might be easier with two batteries as they can be placed symmetrically but that shouldnt be a problem if you are making an IMU controlled quadcopter....
Also wont the point I gave earlier that 1 battery might run out before the other may favour us using a 5000mah 15C battery?

Anwar can you please tell me how you test your quad.. I mean what power supply do you use for testing? Do you keep on using many betteries or do you have a power supply?

I never used 2 x 2200mAH ones together so far. Also, my point is not to fly for 15 minutes. I will be happy with 5 minute flights, landing and changing batteries, and then going up again.  The idea is to keep weight in control, instead of putting undue load on the motors.  The idea is to be flexible enough so that one can try different scenarios.

I have multiple batteries of various mAH ratings to test. 

And my tests currently are short, that gives me enough time to charge others. I test either by holding it up from underneath and slowly increasing the throttle, OR just keeping it on the ground and slowing trying to lift off (sort of relying on my heli flying reflexes to handle any "scenarios" but accidents/toppling does happen, and I am impressed with how the props are holding up, even without a prop-saver setup).

hey anwar..

can u recommend me a motor with much more thrust..at abt 700grams with 3 blade props.....what material did u use for making tha body of your quad.??

If you upgrade the motor, you will likely end up upgrading the ESC as well, so one suggestion would be to go with the 8x4 3 blade props (if you are getting them from HK) and use the motor you suggested.  Keep the frame and battery etc weight to be minimum. I built my frame using balsa, and it weighs next to nothing.

what is the cost of balsa wood...

how about using simple wood beats that is used foe door decoration and others...??
i am intending to use the 6 chnnel rx/tx by hk...would it be appropiate..??

You can also try the aluminum frames that are put on window frames, they are lightweight(thought not compared to balsa) and easy to drill holes into plus they are stronger than balsa wood.

People have built quads from a variety of materials.  Do not kill yourself over such details now.  Use what you can find, including alu frames, carbon rods, balsa sticks, bamboo sticks, lite ply, heli tail booms.... whatever is lying around.  If the overall craft turns out to be heavy and that is causing you issues, then consider tweaking the frame again. 

Of course it is easier to get it right the first time around, but that should be a factor that hinders the progress of your project.

About drilling holes, I can vouch for just cable ties doing this job perfectly, at least for motor mounts.  I have been through a few topplings/crashes so far, and the cable ties are holding strong.  Have one tie cable go around the base of the motor first, then have two tie cables that hold the motor on to the frame stick.  Make sure these two tie cables pass through the first  tie wrapped around the base of the motor.  I think this will be my preferred method for mounting motors, at least on balsa electrics with a properly defined balsa motor mount.

hiii is any1 here for help

hey bro anwar i need u r help..... i m going to make quadrotor....can u help me... my id is ..