I have the [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKBF5&P=M]Great Planes ElectriFly C-35 Mini Brushed ESC w/BEC[/link], the max rated currents for it is 35A continuous. I want to use this battery pack with it: [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9167&Product_Name=Turnig y_1600mAh_3S_20C_Lipo_Pack]Turnigy 1600mAh 3S 20C Lipo Pack[/link]. How do I figure out how much a ESC can handle? What do I need to look at in the battery specs or ESC specs to tell if they are compatible.

You just need to look at the front of the ESC. It says 2-4 lipo, so it will work with a Lipo from 2-4 cells, so what you have will work.

Be careful with the motor, however, you need to choose a prop that doesn't draw too much current for the motor too.
Good Luck,
Curtis

20C equals 32 amps. I would get a larger battery. Of course, it all depends on the flying style/weight of the aircraft you plan on using this with.

There is a chart on the internet. watts per pound, that will give you an idea of what to expect with that combination. 3S is 11.1 volts (nominal) so current times voltage equals watts. 11.1 volts X 35 amps = 388 watts (again, nominal), by the way.


Watts per pound Performance Potential
< 50 watts per pound: Unable to rise off ground
50 to 60 watts per pound: Can rise off ground and perform simple aerobatics
60-75 watts per pound: Easily loops from level flight. More impressive aerobatic performance.
75-100 watts per pound: "Fighter"-like performance. Aggressive climbs
100-150 watts per pound: Extended vertical runs. Unlimited aerobatics
> 150 watts per pound: Wings are unnecessary

Here's another viewpoint from the makers of Eflight:

1 horsepower = 746 watts

Watts can be determined by multiplying ‘volts’ times ‘amps’:

10 volts x 10 amps = 100 watts

We can determine the power requirements for a given model based on these Input Watts Per Pound Guidelines (using the RTF weight of the model, including battery pack):

• 50–70 watts per pound: Minimum level of power for decent performance, good for lightly loaded slow fl yer and park fl yer models

• 70–90 watts per pound: Trainer and slow fl ying scale models • 90–110 watts per pound: Sport aerobatic and fast fl ying scale models

• 110–130 watts per pound: Advanced aerobatic and high speed models

• 130–150 watts per pound; Lightly loaded 3D models and ducted fans

• 150–200+ watts per pound: Unlimited performance aerobatic and 3D models

As a note, these input watts per pound guidelines have been developed based on the typical performance of E-fl iteâ„¢ brushless motors. These guidelines may vary depending on the use of other motors as a direct result of actual motor effi ciency and prop size/effi ciency.

How did you figure out that 20C equals 32 amps? Also here is the plane I want to get for this battery and ESC: [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJCC2&P=0]Great Planes YAK 55 3D Park Flyer EP ARF 33.5" [/link]. This is going to be my second one, the first one got banged up after too many grass landings. Also I want to upgrade the motor but Im having trouble figuring out all this electric stuff, Ive been only flying glow the whole time. I found these really cheap motor esc combo's on hobbycity.com that are getting good reviews. Heres a link to the page of motor combo's: [link=http://www.hobbycity.com/hobbycity/store/uh_listCategoriesAndProducts.asp?catname=Towerpro+ Combos&idCategory=179&ParentCat=192]Motors[/link], which one would work good for my plane, and again what do I need to look at the specs for. Sorry but Im new to the electric stuff. Thanks for the help though.

20C=32amps is kind of a misnomer.
That is what the battery is capable of delivering, not neccesarily what the motor will draw.
Rate your ESC on the motor as far as amp rating.
By the way he figured it by the mah rating.
The battery has a 1600mah rating or 1.6amps for an hour and is capable of 20C or 20X that capacity=32amps BUT at that rate the battery will only last 3 minutes until the 1600ma are used up (actually less since you never want to completely drain a lipo)
The real current draw should be much less than 32 amps, I would be surprised if you draw 10 amps.

Any help on the engine upgrade question?

I can understand your confusion. There is a lot of information out there and specs differ widely by manufacturer. Even the way motors are sized depends on manufacturer. Some spec diameter of the outer can and then the length of the can. Some spec the diameter of the stator, and the length of the stator. I would recommend this combo for you [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4854&Product_Name=TowerP ro_BM2410-08T_/_18A_BEC_/_1047_Prop_Combo]Towerpro combo[/link]
It says that it comes with a 10x4.7 GWS prop, and that is what the Yak recommends. Based on your weight of the plane, i think it will work, but you can get bigger if you want to try things not in combo form. Not sure how the motor is mounted on your plane (looks like a stick mount). You will have to figure this out. You can buy accessories to do a stick mount. I might also recommend LightflightRC.com for good combos and accessories too.
Good luck,
Curtis

Here's a stick mount adapter if you need it. [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6782&Product_Name=Stick_ mount_10mm_stick_/_3g_weight]Adapter[/link]

Thanks for all the info, I also saw that combo as an option. And yes this stuff is confusing at the moment. Im open to any suggestions so if you know of a better combo or engine Im all ears. What would you recommend from that website as far as a good inexpensive brushless setup? Another thing I forgot to ask, with the stock brushed motor there is a gearbox attached, is a gearbox needed for brushless or is it a direct prop to shaft link?

Here is what I am using on my Simple Stick which weighs about 20 ounces with the wheels and about 25 ounces with floats. It is very aerobatic, but not 3D. If you put it on your Yak, I think you could safely bet on being 3D with it.
Here is the motor - [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7705&Product_Name=TGY_Ae rodriveXp_SK_Series_28-26_1000Kv_/_240W]Turnigy SK 28-26-1000[/link]
The ESC - [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6457&Product_Name=Hobbyk ing_SS_Series_18-20A_ESC]Hobbyking Super Simple ESC[/link]
I think you might be able to use that Stick attachment with this motor too. I use a 9x6APC E prop on it and it is fantastic. It has a prop adapter that will mate right up to the motor. You don't use a gearbox, the benefit of the outrunner motors is the windings can be varied so much, that you can find one that will match your voltage and give you a good speed range. My 9x6 will turn in the 7000 RPM range.
Let me know if you have any further questions.
Curtis

Cool thanks for th info, I do have a question. What do the three numbers associated with the engines stand for? I see that most of them have it. 28-26-1000.

In the case of the Turnigy motors, 28 means the outside diameter of the can (which holds the magnets) and the 26 in this case means the length of the can. The 1000 is the kv and that is the number of RPM's per volt you should expect fromt he motor when it is run full throttle and not loaded with a prop. Using this number and the pack configuration, you should be able to size a motor properly. I typically run in the neighborhood of about 7000-10000 RPM with my motors, and I want to load the motor to about 70-80% of the no load speed with the prop (that's usually where the system is most efficient). So I target a no load speed around 9k-10k RPM. With a 3S battery (11.1) I use about a 900-1000 kv motor and with a 6S battery I ould use about a 450-500 kv motor. The 2826 part tells me roughly how large the motor is and how much current and power I can safely put into it.

I hope this helps, at least it is a starting point.
Curtis
P.S. When you are looking at Scorpion and AXI motors or the Towerpro motors, the 2826 would refer to the diameter and length of the stator within the motor (a 2826 AXI is considerably larger than the 2826 Turnigy)

ok well I think I have decided to go with this [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=664&Product_Name=TowerPr o_Brushless_Outrunner_2410-08T_890kv]towerpro motor[/link] since it recommends the 10x4.7 prop. And I will go with the same ESC that you recommended since it sounds like a easy setup. And I will probably get [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6308&Product_Name=ZIPPY_ Flightmax_1300mAh_3S1P_20C]this[/link] battery to power it.

Ok.. first of all, the current available is the MAH rating of the battery pack. And, that is in miliamps per hour, which is what mah means.

So, if it's a 20C pack, then the max available current, for a short period of time that is, is 20 X the mah rating (in theory) which in this case, is 26 amps. 1300 X 20 = 26000 miliamps or 26 amps.

You may wish to re-figure the battery you want to use if you expect to operate a motor/ESC combination that is capable of 35 amps, and that is if you wish to fly for longer than a few minutes.

CGr.

Hey Beach,
I think that is a good setup you have there. On the link to the motor, you will notice there is a chart with different props on different voltages and this one will draw about 10.9A on 11.1, so I think the ESC and the battery will work out well for you. It also says that it will put out about 21oz thrust too, so you should be able to prop hang with it. As far as C goes as CG was stating, the battery is setup to deliver 20C continuous and 25-30C burst, so the 10.9A will be about 8C, which means you should be able to fly at full throttle for less than 7 minutes, but if you are just cruising around doing some loops on less than WOT, then it will extend your runtime. I say go for it.
Curtis
P.S. Don't forget the matching set of bullet connectors. They usually come with the motor, but it looks like this one does not include it. [link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=66]Click me[/link] Too bad you need to buy in a set of 10, but you will need at least three pairs unless you want to solder the ESC directly to the motor, which I wouldn't recommend. You might be able to find a couple of sets at the LHS, but maybe not as cheap as these.

Well, then, I guess it's a waste of time discussing the weight of the aircraft he plans to use this combination on.

Good luck with it.

CGr.

Ok what do you mean by this statement? Im a complete noob to electric flying so if you can find me a better setup please do so, the plane weight is 12- 14 oz. The only reason why I chose that battery was because it seemed towards the lighter side for a 3s 1300 Ma battery. Also Im trying to keep the battery as light as possible, the way the plane is designed the battery sits up in a compartment right behind the motor. SO this makes for a nose heavy plane and the only way to balance is to add weight to the tail. So the lighter the better. But with every post from you guys Im learning a little more. So which battery would be better for my needs? Im all ears so please dont hesitate to lead me in the right direction. Thanks

CG, in post #5 he mentions that he wants to put it into a Great PLanes YAK 54, that's where all of the information comes from.
Curtis