grounding front and rear batts

[Swaggasaur]

So ive been looking on the forums and from what i can tell, there are two ways you can wire a front and rear battery in parallel to get 12v.

You can either run + to + and -to - to the batteries

Or you can run + to + skip the - to - and ground both batteries to a good grounding point.

Im guessing the - to - to both batteries is best, but is it neccessary?

Im going to run a D3400 and an XP750 on a mechman 220a alt.

Amp is an AQ3500 powering 1 DC XL m2 10" at 1 ohm. I dont plan on dishing all 3500w to the sub.

So a bit of voltage drop wont hurt me.

As of right now i was gonna do 2 runs of + and do 2 grounds to the front and rear batt.

To sum it up, do i absolutly need to run another 2 runs of - from the front to the back for this to work?

Thanks for any input

[Blackedout]

No you don't need to run isolated grounds. Make sure your voltage drop from front to back is within 3-5% of your total voltage. (~.5 volt)

Measure your voltage at the front and back with the car on.

[Swaggasaur]

Thanks bro, exactly what i was lookin for

[Blackedout]

If you can't get the voltage from front to rear within a reasonable range after completing the big 3, you should consider going with an isolated ground at that point.

Though, If your grounds are clean and solid, it's usually not a problem.