Newbie here and electrics is not my forte. I can get by with installation of a car stereo and amp but that's as far as it goes. So I own a Series 1 BMW 2007 model and have just had a new AGM battery installed (which lives in the boot) I noticed a few wires coming off the positive end, one isn't connected to anything but the guy left it connected. One wire coming off positive is power supply to my amp. A smaller thinner red wire comes off positive and runs to the front of the car, no idea to what. Lastly is a thicker brown wire which runs to the front but has been electrically taped to a thinner brown wire. The thinner brown wire I have traced goes directly to the rear break lights where several wires have been snipped at the plug end. I have left it alone as my lights to the car all work fine. Just curious why on earth a single wire would be running from the positive to my break lights ( I can only assume at some point someone has messed with it, possibly aftermarket lights fitted or similar). Any ideas.