If I have one battery, is a good or bad idea to run the negative cable from the amp to the battery? Did the chasis have more resistance than, let say, 14ft of 4 gauge cable? I'm asking that because I read that grounding the amplifier at the battery minimize voltage drop, don't know if that is true.

I like to ground the amp to the battery negative when they are close together, I wouldn't run a ground cable all the way from under the hood to the amp in the back though.

I've always wondered this too. Sure it is more expensive, but is it effective. Hopefully some others with experience can chime in.

If you have a car or truck with a frame, you will always have lower resistance grounding to the frame. In some very limited cases with uni-body construction and very poor ground placement you could do better with seperate conductor all the way to the battery.

In my opinion, most people run extra ground wires because they don't understand how they could do it better without running the extra wires... Or they think it looks cool...

I did this in a way. I have a 1/0 cable running from the front battery negative to the heaviest metal in the rear of the van where the rear battery grounds. I have that cable connected to ground lugs at each point along the body where the sheet metal is overlapped and spot welded together. It's definitely overkill but solved quite a few electrical issues I had with windows, door locks, etc. operating correctly and that way I know the ground is solid and probably cannot be improved upon.

I doubt it would do much if anything just to help an amp, but it is commonly done for multiple battery setups from what I've seen. I figure it's got to help on vehicles without full frames under them too, like my mini-van. In vehicles without a full frame there's only the body's sheet metal to transfer the current where a full frame is heavy steel and can handle lots of current flow with much less resistance. You didn't mention the vehicle you're doing this in, but I doubt it would be worth the cost and trouble with only 4awg wire, and especially if it has a full frame under it like a full size truck.

95Honda simplified it much better...

Edited August 31, 201114 yr by Alton

Interesting thanks Honda and alton. Sounds like you had quite a list of issues with grounds?

Dunno about other uni-body vehicles, but my Venture mini-van was horrible. Before I ran that separate ground wire from the front battery to the rear battery I tested the resistance at both points at a whopping 121ohms! After running that ground wire and grounding all the body seams together along that wire it's a nice 1.4 ohms which is much much better.

My car is a 1994 Corolla. I did this today: I ground my head unit to the battery and at high volumes the hu display dimmed. I take it out and ground it to the metal in the engine compartment and the dimming stop. My amp is grounded to the chasis. Is a low powering system but the fuse rating of my amp is 60amp with an alternator of 70amp. I want it to reduce the voltage drop in a simple and cheap way because is a cheap sound system. No need to replace my alt nor adding a second battery, worhtless. Thas why I bring this topic, thanks to all of you :-)