Deans T Plug Parallel Lipo Battery Adaptor 

This Parallel Adaptor is generally used to increase the run time

of Model Aircraft, Boats, Cars etc

so with you connect 2 x 4s 2200mah lipo batteries to the parallel

adaptor the voltage will be the same at 14.8 volts but the mah will be increased to 4400mah achieving a longer flight time

Over many years now this adaptor has proved to be very stable