[TManiaci]

So, we have been having discussions on Electric system setup for aircraft. I thought it might be nice to cover the basics of e-power in a thread dedicated to the technology. It's not as simple as it seems, and actually confusing at first. There are many factors to consider in the selection of hardware to power an aircraft.

All the components have thier own ratings, capacities and performance factors. To properly set up a system the items that make up a "system" need to be selected properly to deliver the most bang for the buck, and provide the least weight for the desired power requirements. The key ingredients in the mix are:

a. Motor: Wattage/Amperage Capacity, kV (rpm/volt),
b. Battery: Voltage, Amperage Capacity, C Ratings
c. ESC: Continuous Amp Rating, Burst Rating, BEC capacity
d. Propeller: Diameter and Pitch
e. Power needs of the Control System

These items all can influence each other. So let's discuss the details of these items and thier attributes that we must consider.

[CA$HEY]

Im in,,im pritty right on everything,EXCEPT,,the 1P,,and 2P thingey

[TManiaci]

The key consideration is to put together a system that will perform to your desired needs. What is desireable is probably the first question to address.

Some may disagree, but it the basic rules-of-thumb FOR 3D Aircraft is probably best described as follows in terms of Wattage, where wattage is the best and easiest measure of electrical power.

Performance of 3D aircraft is one of the most demanding requirements. We all want robust power to pull out of 3D stall speed manuvers. That punch can get you out of trouble, and many 3D acrobatics require monster power to execute. This is probably best described in terms of power to wieght ratio. For e-power, Watts per Ounce or Watts per Pound are the units of measure we can all mathematically derive. The ratings I find best describes our world is as follows:

Under 10 Watts per Ounce = weak, will fly okay but not enough.
10-13 W/oz = Good, where most people fly.
13-15 W/oz = Very good, great pull-out and ample power to do anything.
15-20 W/oz = Strong, more than you need but a helloffa lot of fun.
over 20 W/oz = Stupid power... you really over-did it!

[sandman]

Once you learn the very basics, learn to use a motor power calculator, and then invest in a data logger like the ones from Eagle Tree Systems. With the motor calculation program you can determine battery need, prop selections, etc. and with the logger, you can see if in flight performace matches the predictions. The data logger makes comparing props, batteries, ESCs, motors, much more objective. I have found this invaluable for finding the lightest, most powerful setup for electric aerobatic planes. If you'd more information about using a logger, I'll be happy to contribute here.

I have also developed a simple test to evaluate motor quality.

[TManiaci]

In the simplest terms, the power comes from the battery, is controlled and delivered by the ESC (Electronic Speed Controller) to the Motor and the motor converts the electrical energy into radial motion to turn the propeller.

So, let's start with the power source, the battery. For high current delivery and light wieght, the best option today that is affordable is the Lithium Polymer battery pack, also referred to as Lipo or Lipoly. These little guys really pack a high energy density. So, let's focus on this popular battery type.

Battery ratings are a little cryptic, so let's get that lingo dialed in here.

mAH, or milliAmp-Hours, is the measure of "capacity". 1000 mAH is equal to 1 Amp-Hour (AH). The bigger the number, the more energy that is stored, and the bigger and heavier the battery will be. The units mean the number of Amps the battery will deliver for a given time peiod. So, a 2100 mAH battery will deliver 2100 mA (2.1 A) for 1 hour.

The "C" rating... a measure of Amperage Delivery Capacity. Most Lipo's provide a "Continuous" and a "Burst" rating. The meanings are obvious, and we generally don't engineer our systems to pull more than the Continuous rating at full throttle, often called WOT (Wide-Open Throttle). The "C" is a multiplier of the AH rating. So, a battery that has a mAH rating of 2100 and a 25C rating will deliver the product of the AH x C, or 2.1AH x 25C = 52.5 Amps.

[TManiaci]

Thanks Sandman. You're comments are really appreciated. You are referring to some fairly advanced aspects of this topic. After we get the fundamentals all laid out, let's discuss your experience with loggers. That will tie all the pieces together for everyone.

[snap]

Looking good t-man, I hope we go to lin-bec vs switching bec,then 2.4 with high voltage electric systems vs 72mhz. If you need any info I love to contribute ,I do a class once a month to certify electric flyers at are field.

[TManiaci]

I hope we can cover that and a lot more Snap. I'll need some help with ultra-high power system issues, and the 2.4GHz issues. Let's save that for later after we get basics down.

[snap]

This is very cool, like an online class, looking foward to E-flight 105
lol

[crash]

I'm glad you are doing this TMan, now maybe I can figure out which kv motor I need for a plane. I have always been lost on this.