Get a 450 micro-farad electrolytic capacitor (you can get them from Radio Shack. . .easy)

It will have the positive pole marked - just take an old connector and solder that to the positive wire and the negative to the black. Black should be the OUTSIDE pin and the positive should be the middle (I believe. . .double check. . .) but it's exactly the same as when plugging in a BEC or even your personal transponder - that only taps power and your supplying power. . .