All R/C aircraft have an onboard battery. In the case of Sail Planes, or those with Internal Combustion Engines, the battery is used as power for the receiver and servos. In electric powered aircraft the battery must also run the motor. That is why until recently, small to mid sized electric aircraft were non-existent. Li-Po (Lithium Polymer) battery technology has changed all that. Before Li-Po's the power required just to get the weight of the batteries (Ni-Cads) airborne, was so large that it required a very large aircraft to support it. A Ni-Cad battery cannot discharge more milliamps than it's rated capacity. The technology behind Li-Po's allows them to discharge 10 or even 20 times their rated capacity. In other words, a Ni-Cad pack rated at 1300 mA can discharge at 1300mA. A Li-Po pack of 1300 mA can have a Maximum Continuous Discharge of 17 Amps, yes Amps not Milliamps ! 1.3 amps compared to 17 amps, this is why Small to Mid Sized Electric Aircraft Design and Sales have skyrocketed in the last two years. This has opened a whole new world to the R/C Enthusiast. Let's take a look at some comparisons between two of my personal packs, both of 1300 mA.
 Li-Po is the left, extra connector is for balance charging.
Number of cells 4 3 Weight 4 oz. 2.6 oz. Max. Cont. Discharge 1.3 amps 17 amps Charge time 12+ hours 90 mins. Price $50 $45 State at Discharge the closer to 0v if any cell is allowed to Bear in mind that the Ni-Cad pack is a receiver pack for a Glow powered model with a 60" wingspan and 5 servos and the Li-Po pack is the Motor power and power for 4 servos in a 36" wingspan foam park flyer. To compare apples to apples as far as price goes, I have a 60" wingspan electric model as well. The power for it is 2 Li-Po packs of 3250mA each, about $120 per pack. However, without Li-Po technology, neither of these planes would capable of flying on electric power.
 The Xtra Tuffe from Northeast Sailplanes. The Li-Po pack powers this plane. More and more modelers are being drawn to electric power. There is zero mess, motors are maintenance free, and they make less noise. The noise factor alone allows them to be flown many more places without disrupting the neighbors. Electric powered models can now compete right next to fuel powered models in the same categories at competitions because the technology has advanced enough to make the power to weight ratios practically the same. Li-Po batteries require a different type of charger and Electrics also require an Electronic Speed Controller. By the time you add in the flight line equipment for either type, it really ends up a toss up as far as cost goes. So now the choice really is up to the modeler, you can build and fly nearly any model now using either power source.
If you only fly I/C models, then Li-Po batteries really don't make sense for you. You can use them as "receiver only" batteries but it really doesn't justify the cost of a new charger because you aren't utilizing the massive discharge power of it. You can even find Li-Po cells for your transmitter, but again why ? However if you want to fly electrics you have to have Li-Po batteries, but the availability of more flying sites really makes the investment worth it.
|
Today in Aviation History :
July 30, 1935... Lieutenant Frank Akers of the U.S. Navy becomes the first person to make a "blind" landing at sea. His biplane has a hooded cockpit allowing him to see only his controls and instruments. He lands on the USS Langley.
___________________________
Free paper planes for the kids
www.funpaperairplanes.com www.paperairplanes.co.uk/ www.bestpaperairplanes.com/
www.amazingpaperairplanes.com/
www.10paperairplanes.com/
___________________________
Aviation Weather Links
www.nws.noaa.gov/
www.noaa.gov/wx.html
http://maps.avnwx.com/
www.usairnet.com/weather/
  |
