My girlfriend and I are working on building an rc plane from scratch. We dont have any pior experiance with with rc planes at all, however we have almost completed our fusalage. We are having some difficulties with the electronics though and could use the assistance from this group. Today we tried to setup our electronics that we ordered online and we ended up burning up our esc. The parts that we purchased are as follows:

Sky lipo battery 3 cell 20C 11.1v 4000mAh http://www.nitroplanes.com/77p-sl400...-20c-3333.html

ESC 18A http://www.nitroplanes.com/60aelbrspcoe.html Not sure why this started smoking...

Fly sky 6 ch radio http://www.nitroplanes.com/79p-ct6b-...diosystem.html

BP 16.5 A brushless outrunner 200 watt http://www.bphobbies.com/view.asp?id...p;pid=C3481965

blue bird mirco servo http://www.bphobbies.com/view.asp?id...mp;pid=T557857

Is an 18 Amp ESC too low for this battery. I tried connecting just the battery to the ESC and it became very hot and started smoking right away. If anyone could provide some assistance to wheather these electronics are compatable I would greatly appreciate it.

Thanks so much

Did you get the polarity right when you connected the battery to the ESC? Connecting the wrong way will fry an ESC fast. (I assume that you had not connected the motor at this time).

The thing that will most affect the current the motor draws is the battery volatge and the size of prop you put on it.

Terry

I did not have the motor connected, I simply had the ESC connected to the battery. Is the ESC that I used not strong enough for the battery?

Without the battery connected the ESC should not draw any significant current, irrespective of the size of the battery. The only thing I can think is that either you connected the ESC backwards or it was faulty to begin with.

Did your ESC and battery come with connectors already fitted?

Terry

I did have the ESC connected to the battery and that made it super hot. They did not come with connectors so I just kinda held everything together. Your saying that the ESC should not have drawn any current from that battery?

The ESC will draw a small amount of current without the motor hooked up, but not anywhere near enough to hurt it. They are saying that you either hooked it up backwards and killed it or the ESC was bad from the factory.

OK, so my next question is, is an 18 amp ESC strong enough for the other electronics I've chosen. Obviously I will need to get another ESC. Are all the electronics I have in my first post compatible, also what should I get to connect the battery and ESC, is it a one size fits all kinda thing?

Thanks so much you guys are providing alot of insight!!

The set up will work as long as you put the right size prop on the motor.

For a given battery voltage the motor will always try and run at a particular speed, the bigger the prop the more work it has to do and hence the bigger the currentit will draw from the battery (and through the ESC)

I am not familiar with the motor you have so I can't say what size will be right, maybe someone else can help here. Most common way to connect the battery to the ESC is with what is called Deans connectors.

I do have a couple of electrics but I'm nore into glow/gas powered planes, so I don't claim to be an electrics expert. I can however confirm that connecting an ESC to a battery the wrong way is bad news!


Terry

In order to pick out a motor and esc combination, you really need to know the weight of everything you are putting in the air. You already have the battery, so weigh that. Weight the servos, receiver, fuselage with the wing and tail, everything. Then go to a vendor's web page and get the weight of the motor and esc you would like to use and add it all up.

Read through the following and work it out.

Once done, you will know what wattage you are working with and what motor and esc to buy. Always go to the higher level when figuring out what motor and esc to buy.. if it works out to 17 amp ESC, go to a 20 amp ESC. Match the motor to the esc. If it doesn't match up with what you picked out, move to a motor/esc combination that does, get the weight (should not be that much difference) and work it out again and get the right one.

You should be fine.

Here are some guidelines:

1. Power can be measured in watts. For example: 1 horsepower = 746 watts

2. You determine watts by multiplying ‘volts’ times ‘amps’. Example: 10 volts x 10 amps = 100 watts

Volts x Amps = Watts

Therefore,

Amps = Watts / Volts ( / = divided by ). Simple elementary math.


3. You can determine the power requirements of a model based on the ‘Input Watts Per Pound’ guidelines found below, using the flying weight of the model (with battery):

50-70 watts per pound; Minimum level of power for decent performance, good for lightly loaded slow flyer and park flyer models
70-90 watts per pound; Trainer and slow flying scale models
90-110 watts per pound; Sport aerobatic and fast flying 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 3D and aerobatic models

4. Determine the Input Watts Per Pound required to achieve the desired level of performance:

Example:

Model: E-flite Brio 10 ARF
Estimated Flying Weight w/Battery: 2.1 lbs
Desired Level of Performance: 150-200+ watts per pound; Unlimited performance 3D and aerobatics
2.1 lbs x 150 watts per pound = 315 Input Watts of total power (minimum) required to achieve the desired performance

5. Determine a suitable motor based on the model’s power requirements. In this case, you will need a motor/esc/battery combination for 30 amps continuous... 3 cell LiPo at 11.1 volts (nominal) is 315/11.1=28.xxx amps, round out to the higher 30 amps.

So, get your paper and pencil out and work out the details. Let us know if we can help.



CGr

I've seen CGRetired type out the explanation that electric power systems must be chosen based on the finished plane many times, and he's always right! You get your plane ready first, then pick a power system to run it. To answer your question about your selections being right though, your motor and ESC are appropriate for each other, but your battery is way too big. It won't hurt the motor or esc to run on that battery, but the battery will be too heavy for any air frame appropriate for that motor/esc. If you go much over a pound ready to fly with your completed design (RTF means your total takeoff weight), you're going to be under powered even using the biggest prop and a 3 cell battery.

The motor we have is rated at 200 watts and 16.6 Amps and I dont want to do any hardcore flying. I most likely want to shoot for the trainer category. The 4000mAh battery weighs about 13oz and our plane is made out of foam and does not weigh much. Altogether I expect the plane to weigh about 32oz or 2lbs. Is my battery really to heavy?

Motor is 200 watts. Using 80 watts per pound * 2lbs I get a need of 160 watts right? So the battery shouldn't be a problem?

Also would you guys recommend a 20 Amp esc for me since I fried the first one? Are there any other specs I should look for when choosing an esc for my setup?

You still have not confirmed that you did not connect the ESC to the battery with the wrong polarity or not. You MUST be sure to keep polarity correct.

I think I may have messed up the polarity, I only had it connected that way for less than a second... I guess thats all it takes though. It started smoking after that when I hooked it up correctly

Yep, that sounds like fried ESC!

First electric stuff I got came without connectors. I couldn't find anything about which way the polarity should be on the Deans plugs (no marking on the plugs) so I soldered them all up the same way. As I got new bits I duly sodered connectors on being sure to stick with the same convention.

All way welll until I bought a new ESC that came with a connector already on it! I plugged it in without a thought, with the same results you got. The way I had been connecting my plugs was the opposite of the rest of the galaxy!

BTW, you don't mention battery charger. You know you have to have a special charger for Lipos, and that you have to take some care when charging them.

Terry

Redback, the Deans plug do have polarity marks on them, a + and a - molded into the connectors. Some of the knock offs may not have this embossed marking.

Rodney,
Yes, have seen the markings on the later ones I got, but couldn't find any on the 1st ones I got. Once I started I kept going the same way!

Sometime, when I feel like an evenings soldering I'll change everything around!


Terry

Just an idea, but have you ever thought about contacting a local club, joining and have someone with experience help you? It will be easier and cheaper, plus you get a teacher to explain everything to you right up front.

It's hard to show or explain exactly how for you to build a plane from scratch on the interweb. It's better to have someone in person show you the ropes. I started with a RTF and moved up to a ARF, then a Kit etc. A kit and ARF would explain things with detail how to put your electronics in and etc. If you don't want to join a Club and do it that way I suggested.

It's easy to get way over your head. Personally I leave the Scratch building to the experts until you have enough building time under your belt. JMHO



Pete

Jester is correct. That battery is way to big for the system you have. At 13 oz and a RTF weight of 32qz (which is to heavy for the power system you have) your air frame, covering, motor, esc, will have to be 19oz or less; not impossible or really that hard to do, but your finished plane will fly much better at 16-20oz. When you ask for advice it may be to your advantage to take it. Small heavy planes are difficult to fly.

He says he's building out of foam, so that actually makes it harder to stay under weight. You have to figure every wire, wheel, pushrod, piece of tape, etc. I don't mean to discourage you at all though. Have a great time working on the plane and give it a try. That's how aviation started so enjoy your successes and learn from you failures. I do still believe though that you'll have a more successful first run if you'll go down to a smaller battery.

Should i need to do anything to the battery before I begin using it?

Charge it!

But be sure to use a charger intended for LiPo batteries.

Also, when Lipos first came out a number of people experienced batteries catching fire when being charged. This is really bad news because once started the fire is self sustaining! It is therefore a good idea to charge the battery outside or on a non flammable surface.

I've being using Lipos for a while now, and they aren't that scary, however it never hurts to take a few precautions!

Terry

Would it be a bad idea to plug the battery directly into the motor to confirm it works while i wait for a new esc?

It won't work for a brushless motor.

The ESC feeds current to the windings in a particular way to create a rotating magnetic field which in turn rotates the motor. Connecting directly there is a strong risk that you could damage both the motor and the battery.

Wait until you get the ESC.

Terry