I'm redoing my boat which includes a new front deck capable of supporting a Xi-5 Motorguide tm. It is only a 12 volt, but I'm considering hooking the rear battery up in parallel with the front one for extended run time. This would also satisfy the requirement/recommendation to have a common ground (to prevent electrolysis), but I'm unsure of the wire gauge size to use for a run of approximately 16 feet. I presently use a 2 bank MinnKota on board charger and understand that I should break the connection between the two batteries when charging and could do this with a simple disconnect switch. Would someone who has knowledge/experience please weigh in on this. I will not have any issues with my ff as I use a 12v dry cell battery for it. Also, if I did not connect the two, what size wire should I run just to accomplish the common ground? Feel free to speak about any other issues I may not be considering.