New Quadcopter Build: SK450 Dead Cat

Now that we are back from Florida and parts have arrived, it is time to start the new build.  I salvaged whatever I could from the Flying Flowerpot (may it rest in peace).  Two motors, the four speed controls, battery, flight control, receiver, and camera were all salvageable.  However, I decided to replace some of these parts and to change the configuration of the quadcopter to "Dead Cat" - a non-square quad setup with more room for cameras.  See the picture below for the basic setup, not fully assembled.

The other changes that I plan to make are:

• New flight control system (Pixhawk) with more accurate GPS (LEA-6H).  I bought the genuine 3DR versions instead of the Chinese clones to ensure quality.  My old APM 2.6 system was a Chinese clone and had limitations and unknown quality.
• New receiver (Spektrum AR610).  This receiver is highly regarded compared to the Orange R615X, which has rumors of range issues.  New Spektrum DX6i transmitter.
• Use of a PCB as a frame to distribute battery power, bought from Hobbyking.
• Dead Cat configuration using a conversion kit from Hobbyking.  I made a mistake and assumed that all I needed was the previously mentioned SK450 Dead Cat PCB, but it turns out that you need this plus the Dead Cat conversion kit.
• Full monitoring of power by the control system.  This was included with the Pixhawk.
• A proper cover instead of a flower pot, sourced from Quadrysteria.com.
• Receiver power from the Pixhawk or separate UBEC, not from the ESC's.  This should be higher quality power with less interference.
• Use of loctite on all screws to reduce the chance of loosening with vibration.
• Carbon fiber props.

The new control and radio system are shown below.

Storing LiPo Batteries

I am still coming up to speed on usng LiPo batteries in models.  The latest thing I learned is that you should not store the batteries fully charged, or let them fully discharge.  The prevailing wisdom is that you should store them at 3.85 volts per cell, or 11.55 volts for the 3 cell packs that I am using.

I don't have a fancy charger yet so I was not sure how to get them down to 11.55 volts.  Luckily I remembered enough of my old Circuits class and am enough of a pack rat that I could create my own discharge circuit.

Using an old 50 watt 7.5 ohm resistor, a homemade heatsink for the resistor, some wire, and my newly purchased XT60 connectors, I was able to solder together a discharge circuit.

              + ------------ resistor
 XT60                             /
              - -------------------/

I monitor the voltage with a voltmeter and was able to discharge my packs to 11.55 volts and then store them in a LiPo protective bag (good precaution) on the concrete floor in the basement away from combustible material.  Always stay close to and monitor your batteries continuously when charging or discharging them.

Note that LiPo batteries can be dangerous and you should follow ALL manufacturers' warnings on the use, storage, and charging of these batteries.  I am not an expert and you should check the Internet and the manufacturer of your batteries and charger for accurate information.