How to wire Dual Batteries

[14Fusion]

I have looked through the forum on this, but I suppose I havent used the proper search terms.

I want to hook up a second battery, and need to know if both positive and negative terminals need to be connected or if I can ground the rear battery to the frame. I have a 0 AWG run from my D1200 in the front with a 240A Singer and kind of dont want to put the effort of running the second 0 AWG if I dont need to.

I dont need the second battery, but I had it from a different build that ended up in the junkyard, so I didnt want to waste a good XS D5600 battery.

[reedal]

positive to positive, negative to negative/frame. how much power are you running? Tony D and Tony C did a test video showing that systems over 3kW benefited from running a ground to the front battery's negative terminal.

[ChevyBoy95]

positive to positive, negative to negative/frame. how much power are you running? Tony D and Tony C did a test video showing that systems over 3kW benefited from running a ground to the front battery's negative terminal.

That test was specific to his vehicle, not all vehicles.

[reedal]

positive to positive, negative to negative/frame. how much power are you running? Tony D and Tony C did a test video showing that systems over 3kW benefited from running a ground to the front battery's negative terminal.

That test was specific to his vehicle, not all vehicles.

Fair enough

[ShadeTreeMechanic]

A separate ground might be needed for a unit body vehicle. Full frame vehicles benefit from cutting a hole in the floor to ground directly to the frame. The big 3 would have a ground from the frame to the battery and alt / motor to battery. Also you will need a fuse at the front battery as well as the rear so in the event of an accident the pinched cable will disconnect from both batteries.

[GS300Cali93]

A separate ground might be needed for a unit body vehicle. Full frame vehicles benefit from cutting a hole in the floor to ground directly to the frame. The big 3 would have a ground from the frame to the battery and alt / motor to battery. Also you will need a fuse at the front battery as well as the rear so in the event of an accident the pinched cable will disconnect from both batteries.

I have 98 Subaru. Forester planning on running second. Battery need some detail. Do. I run + to + - to - then second. Battery - to frame? And you said I need a fuse on both ends?

[14Fusion]

positive to positive, negative to negative/frame. how much power are you running? Tony D and Tony C did a test video showing that systems over 3kW benefited from running a ground to the front battery's negative terminal.

Running about 2500 watts at the moment, but Im looking to be able to expand without doing too much extra electrical.

A separate ground might be needed for a unit body vehicle. Full frame vehicles benefit from cutting a hole in the floor to ground directly to the frame. The big 3 would have a ground from the frame to the battery and alt / motor to battery. Also you will need a fuse at the front battery as well as the rear so in the event of an accident the pinched cable will disconnect from both batteries.

I have a unibody, so recommendation is having a negative run from the front battery to the rear? I would hope that just using a factory ground in the rear would work because there is alot of crap behind my firewall making it difficult to run wire. I do have the big three done, H/O alt and have all the fusing required for both batteries.

I suppose I will try using a grounding point in the rear and hope it works, if not ill have to really explore a better manner of running cable to the trunk.