I seem to have an accessory plug on my"05" RSTD by the battery that came stock. I am confused by the plug tip? I don't know how to tap into that style, never saw that look before.
First you need to unplug it, then push out the two little black rubber plugs in the end of it. Then I identified the positive side of the plug so I could install the wires in the correct side of the the portion I unplugged. I striped the wires back (1") on the wire that I plan to install in the plug. Next I tinned the striped wires (soldered), making sure it is tinned back into the wire sheathing. Now identifying which side the positive wire is to be installed I pushed the tinned wire into the hole and pulled it in until the small gripers in the plastic plug is griping the plastic sheathing of the wire with only the tinned wire sticking out. Now duplicate the process with the negative wire side. Next I cut the tinned wires back where they are about 1/2 to 5/8" long. Lastly I plugged the two pieces back together making sure they go into the side of the female plug that the contacts are on. This sounds difficult but if you have done any wiring it will all make sense when you start taking it apart. This save you searching around for the plug with wire pigtails. BTW this is fused @ 5w, which is exactly what my 100w Shark stereo had on the power lead.