I wired my Cobra lights (with daymaker bulbs) to the accessory wire in the headlight bucket. I did not run a relay to the battery. Inside the headlight bucket there is a Honda accessory harness that has 3 wires. 1 ground, 1 12V+ switched, and 1 12V+ switched that cuts out when the high beam is on (on with low beams only). I opted to wire my lights to 12V switched (so they do not cut out when the high beam is on).
This is the harness in the headlight bucket:
The switch relay is under your clutch side cover (either painted or chrome) under your seat. This is where they are on the 1300, I'm not sure about the 1800's (see the link below for which 1800's are different). When you get the no load relay, you will see a harness that matches the relay plug, remove the OEM relay, and put in the no load relay.
This site has a TON of good info:
Replacement Universal Motorcycle Flasher Module | Bareass Choppers Motorcycle Tech Pages
There are cheaper, but this is the one I have:
Standard Flasher Relay (customdynamics.com)
This is the harness in the headlight bucket:

The switch relay is under your clutch side cover (either painted or chrome) under your seat. This is where they are on the 1300, I'm not sure about the 1800's (see the link below for which 1800's are different). When you get the no load relay, you will see a harness that matches the relay plug, remove the OEM relay, and put in the no load relay.
This site has a TON of good info:
Replacement Universal Motorcycle Flasher Module | Bareass Choppers Motorcycle Tech Pages
There are cheaper, but this is the one I have:
Standard Flasher Relay (customdynamics.com)