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Which batteries for HK 500.
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Rotormaster View Drop Down
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Posts: 161 		  Quote Rotormaster Quote  Post ReplyReply Direct Link To This Post Topic: Which batteries for HK 500.
    Posted: 01/Dec/2010 at 5:18pm
Hello there. I am new to R/C flight, and am planning on getting a 500. 

My question is as follows.
Keeping in mind that I am a total beginner and do not need serious power of any kind (let alone 3D performance), would I be able to power a 500 on a single 3S? I am thinking that it should be more than fine, but I would just like to confirm with you guys seeing as though you have had actual experience with this stuff.

I think 20C might be a little too low to run safely and reliably, but maybe 25C and definitely 30C should be ok. 

On paper, I can see that, assuming a 30% efficiency loss through electronics, and a -+10% loss through drive train, 11.1v at a rate of +-916 mA should be more than sufficient for lifting a 1,700 kg weight of the ground. Even if only for a period of around 3 minutes on a 2200 mAh pack. 

On 2200 mAh, a 20C pack should give me around 730 mA per minute, whereas a 25C pack should give around 916 mA per minute.

Of course, just because a pack states 20C does not mean that in real world it will rate at exactly 20C. There is fundamentally a limit to the accuracy of everything, not to mention that efficiency can vary upon a multitude of conditions. Also I really do not know the efficiency of these ESCs and what minimum is required to operate them and the BEC safely and reliably, which is why I am inquiring with you folk who have had the experience with these equipment. (Remember, I am a beginner so I am only going to be hovering)

Any and all help will be greatly appreciated.


Edited by Rotormaster - 01/Dec/2010 at 5:22pm
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colin hoover View Drop Down
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Posts: 106 		  Quote colin hoover Quote  Post ReplyReply Direct Link To This Post Posted: 01/Dec/2010 at 7:06pm
i have a 500gt running 2 3s 2270 bats as 6s so thats 22.2v 2270mha
and get about 3 mins with ok power.
and cant wait to get a couple 6s 3000mha bats for $40 +shipping each to get about 5 mins flight and good power.
i dont know all the math you did to fig it out but after playing with 4-5 450's and 3 400's for 3 years.
2 min flight just wouldent get it.
and your right i wouldent even think of a bat of less then 25c for any E-heli power system.
Just my 2cent worth.
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Posts: 1623 		  Quote wchiro Quote  Post ReplyReply Direct Link To This Post Posted: 01/Dec/2010 at 8:44pm
As a beginner I doubt that you will be hovering, more crashing than anything else.  Seriously I would recommend you to get yourself a good Flight Simulator and practice flying a heli on it.  I do tell the beginners that if you crash your heli on the sim 4 times (which you will easily surpass) the amount of parts you would have to buy will pay for the simulator itself.

The flight sims are pretty accurate in the way the heli flys in real life.  Good sims are Real Flight or Phoenix.  I've heard that the Phoenix is more realistic for heli.
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Posts: 168 		  Quote pigsy Quote  Post ReplyReply Direct Link To This Post Posted: 01/Dec/2010 at 11:32pm

You can get Realflight 5 and phoenix cracked versions for about 15usd that use a usb toggle and plug in your transmitter it what i use.



Edited by pigsy - 01/Dec/2010 at 11:33pm
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Posts: 455 		  Quote hairykarts Quote  Post ReplyReply Direct Link To This Post Posted: 02/Dec/2010 at 1:18pm

Certainly get a simulator.

If you want to use a 3s battery use 2 linked in series . the c.o.g. will probably be wrong if you dont.
There is a thread on this sub forum.
Rob
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Posts: 161 		  Quote Rotormaster Quote  Post ReplyReply Direct Link To This Post Posted: 02/Dec/2010 at 4:45pm
Originally posted by colin hoover

i have a 500gt running 2 3s 2270 bats as 6s so thats 22.2v 2270mha
and get about 3 mins with ok power.
i dont know all the math you did to fig it out but after playing with 4-5 450's and 3 400's for 3 years.
2 min flight just wouldent get it.
and your right i wouldent even think of a bat of less then 25c for any E-heli power system.
Just my 2cent worth.

You only get 3 minutes on 6S? sounds rather poor. What type of flying do you do 3D? I'm guessing you either fly 3D or there is an abnormal inefficiency somewhere.
Also, why do you think that a 20C's 733 mA per minute would not be sufficient to keep a 1700 kg weight of the ground? Do you think it would be unsafe as it could cause the ESC to potentially starve the servos? Such a failure would be my main concern, additionally, I am aware that this is also bad for the battery itself as well. Your two cents are appreciated. 

Originally posted by wchiro

As a beginner I doubt that you will be hovering, more crashing than anything else.  Seriously I would recommend you to get yourself a good Flight Simulator and practice flying a heli on it.

Big smile Oh, common! You do not give much hope, but then again your uprightness on the most likely truth of the matter is much more appreciated than overly hopeful and unrealistic optimism. How hard really is it? keep it coming! You give me ever more anticipation to wield the controls of this little machine. I do like a challenge, but if that is what you think with the 500, than do you think there would be absolutely no chance with the much lighter 450?

Originally posted by wchiro

I do tell the beginners that if you crash your heli on the sim 4 times (which you will easily surpass) the amount of parts you would have to buy will pay for the simulator itself.

Although I appreciate your advice, I need to get this battery information out of the way, if you don't mind. You do have a good point, however. Crashing 4 times on the sim will pay for the sim itself in the money that is thereon saved on parts that would have been spent, had those 4 crashes been with the real model instead of the simulation. Very good thought. 




Edited by Rotormaster - 02/Dec/2010 at 4:50pm
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Posts: 455 		  Quote hairykarts Quote  Post ReplyReply Direct Link To This Post Posted: 02/Dec/2010 at 4:58pm
Believe us all, it is NOT easy. Buy spare feathering shafts , blades, main shafts,upgrade to metal as many parts as poss and check all alignments thoroughly. After you have done that ... go on a simulator . Rob
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Posts: 161 		  Quote Rotormaster Quote  Post ReplyReply Direct Link To This Post Posted: 02/Dec/2010 at 5:00pm
People, although I appreciate your concern, I started this thread because I need your experienced advice on the battery issue. Although I had planed to make a thread regarding sims anyway, can we abstain from turning this thread into one about sims, as you all seem to be doing? 

Originally posted by pigsy

You can get Realflight 5 and phoenix cracked versions for about 15usd that use a usb toggle and plug in your transmitter it what i use.


pigsy, what exactly is this "cracked version"? Also, are not all computer sims controlled by a USB cable that is connected to the transmitter? 

Originally posted by hairykarts

Certainly get a simulator.

If you want to use a 3s battery use 2 linked in series . the c.o.g. will probably be wrong if you dont.
There is a thread on this sub forum.
Rob

C.O.G is not an issue and it is simple to adjust. Is there a reason other than center of gravity that you do not recommend using a single 3S?
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Posts: 1956 		  Quote Mustang Sally Quote  Post ReplyReply Direct Link To This Post Posted: 02/Dec/2010 at 7:22pm
Your choice on batteries will rather depend on the headspeed you want and motor you will use.
A minimal technical knowledge is required for this hobby; please ensure you know the differences between up and down.
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Posts: 5 		  Quote Carbon38 Quote  Post ReplyReply Direct Link To This Post Posted: 02/Dec/2010 at 8:36pm
Originally posted by pigsy

You can get Realflight 5 and phoenix cracked versions for about 15usd that use a usb toggle and plug in your transmitter it what i use.

You should be banned for saying things like that...
 
Anyway, learning on a simulator is absolutely neccessary imo
 
Originally posted by Rotormaster

C.O.G is not an issue and it is simple to adjust. Is there a reason other than center of gravity that you do not recommend using a single 3S?
 
it is quite simple to adjust the c.o.g on a plane but on this heli, you don't have a lot of space to move the battery pack (don't forget the canopy). I made some measurement last evening and you will need about 0,7kg of battery to get a correct c.o.g.
 
One other point is the Kv of your motor. you probably know that Kv * Voltage = rpm. Don't forget the gearing wich reduce the speed of the main rotor. You should keep at least 1500/2000 rpm to the main rotor.
 
So make your own calculation and choose your battery pack (and eventually your motor pinion)
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