I have a 2005 ultra classic. Saturday I decided to upgrade the turn signals to led and change out the headlights to led as well. Everything was plug and play and I installed the badlands hyper flash control module. When I got finished I hooked up the battery and turned the key on and tested everything. All lights worked radio etc. etc. I went to start it put it in neutral and turned the ignition switch on waited on fuel pump to stop and hit the starter button. I heard a loud clunk and lost all power. Turned the key off and back on and lights were dim and radio would not turn on and gauges flickering. I booked up a small half dead jump box and everything came back to life hit the starter button and click click click click like a low battery. Battery 3 years old. Took battery and got a brand new one. Charged it over night and the next morning same thing. Loud clunk and nothing. Took cap off solenoid pushed it in and nothing. Jumper wire from battery to solenoid nothing. So now I’m thinking crap starter is shot. Original starter with 47k miles. Went to the dealership got new starter, starter relay, and voltage regulator. Installed everything hooked up a charged battery and what do you know. Nothing still doing the same thing. I have checked all my grounds that I can find. Checked all fuses. Voltage meter shows battery at 12.8 and when I hit the start button it drops down to 3 to 4 to 5 volts. Any and all help would be greatly appreciated I’m only off work every other weekend and I’m trying to get some much needed 2 wheel therapy. Forgot to say I even put all the original lights back in and nothing changed. Thanks everyone and sorry for the poor grammar. I’m using a phone and pretty upset.