johncsi

I actually own a Lincoln MKZ, which is the exact same car with a little extras, and I leased it back in 2015. That makes it a little over 2 years old. This car has been plagued with dead 12 volt battery problems from the start, 5 dealer tries and 2 batteries and have finally won a settlement from Ford. I really don't like it, but it is better than nothing. So, now what I would like to do is install a second battery in the trunk. It would not always be connected, but it is a little difficult to know where to attach the ground. As I said before, this MKZ Hybrid is the same as a Ford fusion; in fact they have the same wiring diagram. On the negative terminal there is a battery monitor attached to the battery and from there a larger (maybe #9) wire attaches to that small module and then to ground. It also is connected to the positive side of the battery. If I went this route, where would be the best place to connect the negative side? To the battery or the frame after the battery monitor? And just in case you think there is no recourse about a dead battery, all information was in my owner's manual and a key for the vehicle is either attached to one of the teeny tiny 3" x 2" key fobs, or in them by prying them open. You can then get into the vehicle and under the hood and get to the main or high powered battery fuse box. On the driver's side on the left side of the box is a place to connect the + from another battery. Then attach the - to a bolt toward the back.