I used the frame because its the best direct path to the battery. If you did the Big 3 it is even more wise to go to the frame on the same side the battery is grounded.
Best would be a pos and neg run right from the battery. Just not as cost effective.
SInce when was the battery part of the circuit path from the alternator?
Electron flow is
Alternator ground to negative on the amp,
thru the device and out the positive amp terminal
then back to the alternator's +
I see no battery there...
nor is there any "ground" in a 12V DC circuit. There is only Positive and negative.
Thehoe92: I agree re: more & more incorrect info.
However, the first paragraph of your post is symptomatic of the cancer afflicting this forum... I'm sorry but... you are 100% wrong.
The alternator/engine block/transmission is your 'ground'... Now Which is connected to the drivetrain directly in multiple places, the body/chassis assembly or the battery?
The body OR the chassis (and especially both bolted together) is the largest most current flowing damn wire you can have. Big enough to flow LIGHTNING without damage. It is so large a "wire" you can essentially ignore it or consider it as having 0 resistance (though the wires completing the circuit do have resistance)
The issue on SOME VEHICLES is there can be a piece of sheet metal that is bonded in place or uses plastic fasteners, rather than being welded or securely bolted. Or maybe it has only the equivalent of a tack-weld connecting it. Connecting an amp to those would have poor electrical continuity to the body shell.
A seat frame is a structural component, and will have one of/if not the best connection to the chassis/shell possible. Lots of surface area and Huge cross section.
The really ****** thing about doing it the way you suggest is this:
1: the current capacity & voltage drop/resistance of a wire is inverse to its length. 6" of 8 gauge has less resistance and voltage drop than 20ft of 1/0!
2: if you ever have an issue with your battery to chassis ground or battery to engine block for whatever reason (loose bolt, corrosion inside the wire or terminal are the most common), then you have provided an alternate path for the starter motor to source 'battery negative' thru your stereo equipment.
IE: thru your amp's negative to the rca ground shield to the head unit's chassis negative, to the driveline to the chassis straps.
If the amp is mounted to chassis metal with conductive hardware, you might get lucky and just have it flow thru the amp circuit board to the amp shell and thru the bolts back to the chassis.
It lets the magic smoke out of your devices VERY VERY effectively.
"But I have a circuit breaker/fuse on my battery wire!!!"- Anonymous dufus
-Since power is not flowing on the positive side of the aftermarket amp circuit, you won;t even pop your + circuit breaker/fuse when 300amps runs thru your equipment.
To further prove the battery isn;t in the circuit---
You don't even NEED a battery for a vehicle (and it's electrical systems) to operate if the engine is running... Batteries weren't placed in cars until 1911! Model Ts, for example, didn't get batteries standard until 1926, 9 years after electric headlights.
If all the above doesn;t convince ALL OF YOU that the battery is NOT the "ideal" place to connect your negative wire, nothing will.
Even in my BMW with a convenient rear mounted battery, I used chassis 'ground'...
In my MGB, same, even though that was only 1" from the battery negative.
DSM, same, and it was front mounted battery...
and 3 times I have seen someone attach a neg. amp lead to the battery and fry their equipment.
