There is no noise, if there was a noise, it would scare me.I know this is an older post but have a question about your battery tender. I connected my NOCO genius directly to the battery at first and when I plugged it in and turned it on I was getting a clicking noise coming from the fuse box does your truck make any noises when the tender is on? I have since moved the negative from the battery to a ground close to the battery. I have not turned it back on yet to see if I am still getting the clicking noise form the fuse box. I only installed the tender due to I go out of the country for work for about 3-4 months and the wife will drive the truck but not very often.