So I recently purchased a D3400 for my build, it was going to replace my stock battery. Well, it doesnt fit, I swear I measured three times Well I decided to just buy a D1200 to replace my stock battery and mount the D3400 in the trunk. Two questions, Do I have to run a ground from battery to battery or is okay to ground the battery in the back, to the frame? and Which battery do I run off of to my amps?