running an Ign wire?

im running a fuse block in the back of a car im workin on im running 3 screens,reverse camera,video amp,power inverter,neons,etc.. and want it to come on with the ign. now i figured id run a 10ga cable off the ign wire at the key (2000 BMW 328ci)and run it to the fuse block. now should i run a relay to that the to the block or run relays after the black to each component??? also how do i conect the 10ga to the wire itself will it be of to solder that thick wire to a smaller one?? or is there a better way to do what i want thanks

its ok to run all the accessories off of one relay its not going to draw to much???i was going to run a realyoff of each fuse. also how would i conect the 10 gauge cable(is that thick enough or to thick??) to the ign wire just solder and tape it ok? thanks

Most Bosch type relays are going to be good up to 30 amps. The relay should have this stamped on it for that matter. You are not running a 10 guage line to the ignition wire at all. You are running a small primary wire to the main ignition line. This line (fused at the ignition) then turns on the relay at the back of the car where your equipment is going to be. Look closer at the diagram.Top Secret, I can tell you but then my wife will kill me.

ok i understand now so instead of 30 going to each accessory it will go to the fuse block input and then each fused terminal will go to what i want it to go.. so instead of running 10 gauge run like a 16ga wire and them maybe use the 10-14 gauge or so for the constant 12v to the relay thanks