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Battery selection

Old 04-24-2013, 05:27 PM
  #1  
GaryJ
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Question Battery selection

Motors,esc's,props.recievers,batteries,etc so many items all with there own numbers.Finding it difficult to match components w/each other.Original power system I put together has motors that just don't look right on plane(RC 2212-6 outrunners)Ultimately decided to go with a pair GWS gw/eps 100-280 brushed motors wich look more suitable to plane.Now I have to choose a battery and find myself swimming in numbers again.Moto-Calc's recommendation for my system is a Kokam 3 cell 360shd 20c 360mAh 3.7 volts.Only thing I get on a search for this batt is a page from german website about tech characteristics.Trying to find equivalant and can't seem to get my head around all these numbers.Somebody PLEASE point out some inexspensive alternates can't seem to find any 360mAh mostley 400 or over and am I correct that I need a batt that is a total of11.1v(3 cells @ 3.7x3=11.1v??)

Last edited by GaryJ; 04-24-2013 at 05:48 PM.
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Old 04-24-2013, 06:09 PM
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rreid7
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My favorite source for batteries and many other items is HeadsUp RC. In addition to good prices and great customer service they include a lot of useful information on their site.

Here's a link to the equivalent battery you are looking for:
http://www.headsuphobby.com/111v-350...tery-F-279.htm
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Old 04-24-2013, 06:14 PM
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Originally Posted by rreid7 View Post
My favorite source for batteries and many other items is HeadsUp RC. In addition to good prices and great customer service they include a lot of useful information on their site.

Here's a link to the equivalent battery you are looking for:
http://www.headsuphobby.com/111v-350...tery-F-279.htm

+1 on Heads Up Rc

great place for information and parts with excellent customer service
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Old 04-24-2013, 06:16 PM
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GaryJ
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Moto-Calc says 360mAh and your recommendation is a 350mAh is the 10mAh difference that negligible or would I be better off with a 400mAh
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Old 04-24-2013, 06:20 PM
  #5  
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It is difficult to answer your question without knowing more about the plane you are building.
It sounds like you are building a twin engine plane.
The motor you mention requires, if I can remember correctly, either 7.2 or 8.4 volts.
I don't think you can run this motor with a lipo pack. You will need to get a NIMH battery pack for it and a brushed ESC.
I highly recommend going with a brushless setup as it will be lighter, and provide more power with longer flight times.
Try doing a google search for your build and see what others have used in their build with success.
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Old 04-24-2013, 06:40 PM
  #6  
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My favorite for batteries is Nitroplanes.com / Hobbypartz.com (same place)

Sky LiPo 20C 4000 mah 4S packs X 3 (for 12S) in a plane with a BVM 5612 EVF... 5000 watts at 105 amps peak power.


Sure, I could get the 40C and get 5500 watts... at double the cost. Its not enough of a difference to matter and higher power = lower flight time unless you increase capacity too.

************

You can run ANY motor with a LiPo pack. You can use ANY ESC with a LiPo.
You must use a brushed type ESC with a brushed motor... 2 wires between ESC and motor.
You must use a brushless type ESC with a brushless motor... 3 wires between ESC and motor.

Select the cell count so the voltage is in the operating range of the motor and ESC. if that range is 7.2 to 8.4 then a 2S LiPo is ideal (8.4 peak, 7.4 nominal)

The issue that arises is the LVC setting capability of the ESC.
Some do not have LiPo safe LVC settings and then you need to be careful not to over-discharge.

But it still works... You can usually see a loss of performance before the LVC triggers even with a LiPo safe LVC setting.

Land at the loss of performance. Its usually noticed at appx 20% capacity left in the pack.

LiPos survive far more charge-discharge cycles if you don't discharge below appx 20% left in the pack.

I have 4 yr old packs used in that big EDF model that are just starting to show laco of ability to deliver rated current.
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Old 04-24-2013, 06:41 PM
  #7  
GaryJ
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oops should have said plane is a 1909 Wright Military Flyer 41in ws, wing area of 530 sq in,wing load of 3.6oz sq in weight before motor,batt and esc is approx 10 oz.Flying weight is approx15-17 oz
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Old 04-24-2013, 06:47 PM
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Originally Posted by GaryJ View Post
oops should have said plane is a 1909 Wright Military Flyer 41in ws, wing area of 530 sq in,wing load of 3.6oz sq in weight before motor,batt and esc is approx 10 oz.Flying weight is approx15-17 oz
Small.. appx 500mah... 2S LiPo. Should give it a decent flight time with lower weight than using a NiCd that would give HALF the flight time.

http://www.nitroplanes.com/skylipo2s.html

The 2S 350mah or the 2S 500mah will serve just fine.

Note that the 3S recommendation of motocalc can also be followed... just look down the page for the 3S 350 mah
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Old 04-25-2013, 04:24 PM
  #9  
GaryJ
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The more info I get it seems the more confused I am.Let's see if I got this all right.When it comes to the mAh rating a higher number than recommended won't hurt,it will just increase flying time because it holds more power?the total number of cells governs the voltage?So if I have a 3 cell batt and each cell is rated at 3.7 v then my total voltage adds up to 11.1?And the 20c number indicates the max current discharge.If a higher discharge rate is used then the esc must match or be higher?The problem a 2 cell is that moto-calc says power w/ this batt would make take off and landing difficult.An experienced pilot could probably overcome that difficulty,but I could not.To me ease of take off and landing very important.Once in the air I figure the sedate flying characteristic(and being only rudder,cannard and throttle)should make it fairly easy to fly even for a non-pilot like me.
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Old 04-25-2013, 04:41 PM
  #10  
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Default kit recommended schematic

This is the kit recommended system.Probably would have gone with that,but dare wanted $110 for motors,esc and batt.Thought that was way over my budget as are most of the motor recommendations given me here $40 and up,not gonna happen.
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Old 04-25-2013, 05:27 PM
  #11  
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Originally Posted by GaryJ View Post
The more info I get it seems the more confused I am.Let's see if I got this all right.When it comes to the mAh rating a higher number than recommended won't hurt,it will just increase flying time because it holds more power?the total number of cells governs the voltage?So if I have a 3 cell batt and each cell is rated at 3.7 v then my total voltage adds up to 11.1?And the 20c number indicates the max current discharge.If a higher discharge rate is used then the esc must match or be higher?The problem a 2 cell is that moto-calc says power w/ this batt would make take off and landing difficult.An experienced pilot could probably overcome that difficulty,but I could not.To me ease of take off and landing very important.Once in the air I figure the sedate flying characteristic(and being only rudder,cannard and throttle)should make it fairly easy to fly even for a non-pilot like me.
Discharge rating of the pack indicates maximum current the pack can deliver... if the ESC and motor demand it. With 20C rated packs that means you should be able to drain the pack in 3 minutes without hurting the pack.
We generally want to be able to fly longer than that on one charge...
I just make sure the pack is rated high enough capacity for the desired flight time (if that much battery size/weight can fit in the airplane) Since its hard to find less than 20C rated packs now I'm not too concerned about C rating.

Moto-calc lies a bit... I have had it say the plane simply couldn't fly at all and my airplane was capable of the full AMA Advanced Pattern Aerobatics sequence.
Moto-calc doesn't understand Canards or biplanes at all, especially something like the Wright Flyers.

The size and weight of your model... a 2S pack should easily give adequate power.

Motocalc tries to tell me I'll need 3S and 2 X 50 watt motors in a plane that has been proven to fly on 2S and 2 X 10 watt motors...
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXTKS4

http://www.bphobbies.com/view.asp?id=V504635&pid=gws103 (discontinued)
Weight: 29.92 grams
Gear ratio: 3.50
Indoor Power System Parts Schematic
All our IPS power systems and replacement motors have carbon brushes. Running your IPS motor above 11 watts you will need a heat sink. You will greatly decrease the IPS motor life on 8.4V or 9.6V.
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Old 04-25-2013, 05:44 PM
  #12  
GaryJ
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Ok makes sense that moto calc "lies" as sometimes seems the info given conflicts with what I'm told on this forum.This is probably where most of my confusion comes from.i've already ordered (before any of this discussion)a turnigy 1000mAh 2s 20c lipo.Would this battery be sufficent for my needs?
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Old 04-25-2013, 05:56 PM
  #13  
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2S 1000 mah will be a bit heavy and require more power...

The plane can probably lift it but won't fly in a scale manner at that weight.
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Old 04-25-2013, 06:05 PM
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GaryJ
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Ok 500mAh?
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Old 04-25-2013, 07:16 PM
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Originally Posted by GaryJ View Post
Ok 500mAh?
I'm gonna disagree with the advice offered so far. This is not a tiny model. A 41" span biplane weighing 17oz is a fair size. As a rule of thumb guideline LiPo battery weight should be at least 20% of the model flying weight (more in most cases). That means a battery of 17 x 0.2 = 3.4oz (95g)

That would put you in the region of a 2s 1500-1600mAh or a 3s 1000-1100mAh. Trying to fly a model of that size and weight on a 2s 350mAh or 500mah would probably mean the battery couldn't deliver enough power and if it did flight time would be ridiculously short.

By the way... is this your first RC model? If so I'd strongly suggest you put it away for safe keeping and get a trainer to learn how to fly. Trying to learn on a plane like this is 100% certain to have a bad outcome and it would be a shame to destroy all the hard work that's gone into building the plane.

While on the subject of crashing I saw you planned to fly on rudder and elevator; i'm afraid that wont work. This plane has no dihedral so will be uncontrollable on rudder only. You either would need to add dihedral or rig up ailerons or wing warping (the original plane used wing warping)
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Old 04-25-2013, 07:29 PM
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Flying weight is approx 15oz after addition of motor,esc and batt.8.3oz before addition of flight pkg and doping .Aircraft designed by Paul Trittle to fly with rudder and cannard.wings DO have some dehidral.Wing tips approx 1/2in higher than center in a "gentle curve"as required by kit plans.Another example of conflicting information that has me seriously considering scrapping the whole project.All I wanted was for someone to put themselves in my shoes and empty pockets and say this is how to get flying
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Old 04-25-2013, 07:41 PM
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Originally Posted by GaryJ View Post
Flying weight is approx 15oz after addition of motor,esc and batt.8.3oz before addition of flight pkg and doping .Aircraft designed by Paul Trittle to fly with rudder and cannard.wings DO have some dehidral.Wing tips approx 1/2in higher than center in a "gentle curve"as required by kit plans.Another example of conflicting information that has me seriously considering scrapping the whole project.All I wanted was for someone to put themselves in my shoes and empty pockets and say this is how to get flying
Sorry, the photos looked like the wings were flat. If it has dihedral then it should turn on rudder ok, Pat knows what he's doing so i'm sure it flies ok.

But have you flown before?

PS... see my comment on motors on the other thread for motor selection.
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Old 04-25-2013, 07:46 PM
  #18  
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Originally Posted by GaryJ View Post
Flying weight is approx 15oz after addition of motor,esc and batt.8.3oz before addition
that's a bit less than you said before, so battery can possibly come down in size a bit, maybe a 2s 1300-1500 or a 3s 800-1000.
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Old 04-25-2013, 08:18 PM
  #19  
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lost a couple oz's by eliminating pilot figure.I was gonna use one of my grandson's pokemon action fig (5in tall )
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Old 05-02-2013, 10:49 PM
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Guys,,
Here a possible game changer to RC batteries. From Ni-cad to Lipo to this?

http://www.engineering.com/DesignerE...cKHvio.twitter
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Old 05-02-2013, 11:18 PM
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Outstanding.One of my fields of interest is nano technology and quantum physics.Can't say I fully understand the math parts but I usually get the idea.Anyway the reasearch concerning nano batteries has been in the works for a while.Kudos to the team that made the power/energy ratio break thru.I'll bet when these new batteries are ready for the consumer market they will cost an arm and a leg





(who would have thought that the guy who doesn't understand electricity would understand quantum physics???)
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Old 06-13-2013, 12:44 PM
  #22  
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Got these LiPo batteries at lowest price. Better deals on other stuff too.
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Old 06-19-2013, 02:56 AM
  #23  
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Figured I'd post my question here rather than start yet another thread.
I purchased this plane.http://www.nitroplanes.com/95a387-21792-bf109-arf.html

I have been looking at 800 mah batteries but they range from 20c to 35c.
I don't want to fry anything, and am confused about the C rating. I am not sure what c rating would be best for this plane.
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Old 06-19-2013, 03:19 AM
  #24  
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C rating is maximum discharge rate. For general purpose 20C will be adequate. I drive my 5000 watt EDF with 20C batteries.

Higher C will have lower internal resistance and thus give a little more power, but I don't find enough difference to be worth the cost to me.

I could drain my packs in 3 minutes (and a couple of my planes are capable of operating at that level of power) which is operating at 20C. I try to manage throttle and/or battery capacity aiming for 6 to 12 min flight times.

As battery costs come down I may opt for the 30C... later.

"YMMV" but unless you need the higher C for competition I don't really see the need.
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Old 06-19-2013, 03:59 AM
  #25  
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I agree with Fred but I do find many of the C-ratings over-rated. More marketing than anything. I have a Genesis 1000mah 4S that says it 65C. Yeah right.

My new best friend for lipos is: www.chinahobyline.com. US warehouse. Great service. Top quality lipos and excellent prices. All the good and none of the bad. orth checking out. I just ordered a 14.8V 3300mah 4S 30 C for $34.00 shipped. Pretty darn good IMO. Check em out !
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