The OEM battery in my 09 C14 finally died for good and I had to replace it. I took out the old, took it with me in case they wanted it for a core charge, and bought the new one. I had a few things to do so I didn't get around to putting it in til the next day. Got it installed and the bike cranked right up........... but........... none of my add-ons were working. No power to my GPS, back-off module was not supplying power to my brake lights, my air horn was silent, etc..... I added an extra fusebox under the seat that houses all my fuses and they were all good. I checked the couple in line fuses near the battery and they were good. I started removing plastic and tracing all my wiring. Then I got to a relay that I added to supply power to the fuse box when the ignition is on. The relay wasn't clicking and was not supplying power to the fusebox. Replaced the relay and all is good again. I have probably used 50 relays since my teenage years in all kinds of different automotive applications. I have never had one stop working. Maybe I have been lucky or maybe this one was just bad, but it only lasted 3 years. So, the moral of the story....... when you have checked everything else, it might be the relay.