Matching battery to motor - What fits what? Newbie Question

[LoopBaCK]

I'm new to electrics. Been flying nitro's and more recently gassers for years. Recently got a Swift with a Century 600 motor, CC HV45 ESC and a 7s eMoli battery - just to get my feet wet with electrics. I'm getting more and more hooked on electric each day! Now that I love electrics I need to learn a little more about them...

I'm interested in getting a few more batteries and adding a second electric to my small fleet. Here's where I stumble. Please forgive the very "newbie-to-electrics" question (I tried several search queries but didn't find what I need). Can someone please explain how to take a given motor and know what ESC and battery combo to use? Also how to mix and match the whole setup - even changing gears to get different results? Not to get too broad, my question really focuses on how to know what battery will work (and how well) with what battery.

If it's already been presented please provide link (and sorry for the redundancy).

[jrohland]

Ok this is a big topic but, I'll take a stab at it.

Volts = speed
Amps (current) = torque
Milli Amp Hours (MAH) = flight time
Watts = power

To start, determine what flying style you want to exercise; Somewhere between basic hovering and radical 3D.

Flying style determines the headspeed you want. If you don't know that, check with the heli manufacturer and people who fly that model. And, indirectly, what MAH your battery packs need.

Just like a polluter, the more "fuel" (MAH) you carry, the longer the flights, the heavier the bird and the slower the response.

To set the head speed, determine the range of main ratios available for your model. From that, determine the RPM you want your motor to max out at. As a general rule, I use 25,000 RPM as the top motor speed. Most brushless motors work most efficiently at, or near their maximum RPM rating.

Motor speed is specified by the Kv spec. Kv is RPMx1000 per volt. So, to get 25,000 RPM from 14.8 volts (a 4 cell pack), you want a motor with a 1750 Kv spec (remember motors range from 80 to 90% efficiency). The Kv you want might be different.

Next, determine the current your motor will draw to maintain the desired headspeed under average load. Unfortunately, there is no easy way to do this. As a result, most of us ask other folks with the same model which motor they use.

Now that you have the voltage you want to run and the average current your motor will draw, you know how many cells your battery pack should have and the C spec you want for your packs. Also, you now know the voltage and amp rating for your ESC. C spec determines how many amps the battery can delivery over a period of time. Most modern (generation II) cells do around 15C. Generation III cells are doing 25C.

If you do everything right, you should get:

About 6 to 8 minutes of hard flying on a charge.
Snappy response to stick inputs.
Motor temperatures no higher than 160 degrees (F).
ESC temperatures no higher than 140 degrees (F).
Battery temps no higher than 140 degrees (F).

I hope this helps.
jrohland

[LoopBaCK]

Sorry I didn't get back sooner...

Thanks, jrohland!!! Yes, that helps tremendously. Exactly what I was needing to gain an understanding.

Thank You!