2001 bmw e46 whelen fire siren advice

Hello, First of all please excuse me for bothering you all, I am not an automobile technician and I am only here after reading about you online. Any help and advice I can find is very much appreciated! We are currently putting together a show vehicle for our business and have bought a siren / air horn unit for our vehicle. We are in the process of installing it and I hoped you'd be able to help. The vehicle has no cigarette lighter but the live cabling is in place. It is possible connect the positive and the ground direct from the cigarette lighter rather than wire directly to the battery? We have been trying this today but we seem to keep blowing fuses on the siren unit and we are not sure why this is happening. Any advice is very much appreciated. The manual for our siren can be found here: http://elightbars.org/documents/reviews/295hf100/295hf100.pdf

The problem with 'normal' sized cig sockets is that at best they are rated for 15A but many have difficulties supplying a few Amps and can melt or flame trying top do so. Unless it's the newer smaller (Merit, Euro etc) socket, I would not recommend drawing 15A from it. The internal fuse is 15A? (20A for other 295HF models.) Try it direct off the battery and see if it blows. If it doesn't, then the 'blowing' supply is insufficient - you'll need a better supply.

Use one of the thick red primary colour wires either at the fuse box, ignition switch or lighting switch or the thick red in the right hand side floor loom then a 15 amp fuse. The battery is in the trunk but you could pick up at the jump charge point in the engine bay, run a smaller gauge from your switch to the relay.

Thank you both so much for your help. I will try both of these things today. I never thought as a newbie I would get such kind support! :) Thank you again.