A123 Battery Cells For the Radio Control Model Airplane
Electric model airplanes have been around for roughly three decades. A big problem in the early days was battery energy density. In other words, they just weighed an excessive amount of for that amount of juice you have access to out of them. This example has improved dramatically recently with the advent of Li-Poly cells, but a battery pack for a larger model can certainly cost big money. The advent of electric cars, such as the Toyota Prius has spurred an enormous amount of research into new battery technologies. In this post, I will describe a substitute for Li-Poly batteries that provides intriguing possibilities.
Thunder PowerA123 Systems produces Lithium-Ion Nanophosphate cells. These cells possess a nominal voltage of 3.3 volts and will withstand continuous discharge rates of 30C. They may be safely discharged as a result of 2.0 volts. The voltage remains fairly constant with the discharge cycle, nevertheless they will have a sharp drop-off by the end. Expect 300 cycles before you notice any lowering of capacity while at 1,000 cycles you will have 75% of the original capacity. They're very safe and secure. Overcharging or over discharging is not going to cause a surge and will have little effect on the life from the battery. Balancing cells if they are charged continues to be a good idea, but not absolutely required. They can be charged immediately after used in Fifteen minutes.
The cells can be purchased in two sizes. The initial M1 cell includes a capacity of 2.3 Ah and weighs 70 grams (2.47 oz). A newer, smaller size can hold 1.1 Ah and weighs 40 grams (1.41 oz).
The key source for A123 M1 cells may be DeWalt 36-volt portable power-tool battery pack. Each pack contains 10cells. I purchased 2 of these for $100 each through Ebay. The costs appear to have risen recently towards the $120-$130 range. Single cells can also be purchased online for $15 from a growing variety of vendors. You'll find a couple of the smaller cells inside a Black & Decker VPX battery pack which will cost you about $15. The smaller cells can be had for $12.50 each.
There are many Li-Poly chargers that support or can be modified to aid the charging of those A123 cells. Because of the sharp voltage drop-off when discharged, maybe you are better off utilizing a timer whenever you fly. Otherwise you need your ESC to shut from the motor when 2.0 volts per cell is reached.
Important thing? These cells provide you with 70% the power density of Li-Polys for about 45% from the price. For a lot of folks, that's a good trade-off. They may be extremely safe and could be charged in Quarter-hour. Should you end up buying half as much battery packs due to the shorter charge time, they be a greater value.