Third wire (it's actually 3 separate wires connected to a small connector...) is for balancing, it plugs into the charger or an adapter board that connects to the charger - depends on the charger - it allows charger to monitor the individual cell voltages and adjust (balance) the voltages between cells. That link explains this kind of stuff.

Sorry, didn't realize you're from Aust - the lipo was in the USA warehouse and HK has an Aust warehouse - just find the same one in the Aust warehouse.

For a charger, this one will work -

http://www.hobbyking.com/hobbyking/s...wer_COPY_.html

This is the orig charger, not the copy linked above -

http://www.hobbyking.com/hobbyking/s..._GENUINE_.html

Get the genuine one, its better quality.