Wiring configuration for multiple amps

[bake0296]

Hey Guys,
I have just installed three amps in my boat with a 3 battery bank. Do I ground each amp on a battery or can I ground them on the Tower? The tower has a 1/2 bolt that comes through under the dash and I was thinking of grounding them on that solid unpainted bolt. Would it make any difference in grounding them there or on the batteries? It is just completing the circuit right?

Thanks

[lee]

You must ground to the batteries. The tower is not a grounding point.

[spharis]

Second that.

If you want to ground to a central bolt, you can either buy a non-fused distro block and tie it in, or you can epoxy or screw a block of wood with a bolt through it somewhere near the battery and tie everything to it; basically a homemade distro block.

[bake0296]

I read something about the grounding as a positive-posititve grounding system vs a positive-negative grounding system. I know one is similar to a car amp where your positive goes to the amp, negative goes to the car chasis. The other is grounding right back to the battery power source negative. Is there a major difference between the two? Is it better to wire my battery bank in series or parallel? Does it matter?

Thanks

[spharis]

I read something about the grounding as a positive-posititve grounding system vs a positive-negative grounding system.

You lost me there. Some older vintage and British cars had a positive grounding system, but it was in the wiring only. The battery was still the same. It was based on the theory of current flow; of course was not a really good idea as it broke standards so it went away; or I hope it did anyway. Alot of people seem to forget that electrons travel from negative to positive. Using a car chassis therefore puts the weakest part of the wiring at the first part of the current travel. Reversing this would be a more efficient way to wire.

I know one is similar to a car amp where your positive goes to the amp, negative goes to the car chasis. The other is grounding right back to the battery power source negative. Is there a major difference between the two?

There is no difference between the two other than a greater chance of ground loop in an auto. Since we are talking about boats, ground to either a grounding lug tied to the battery, or all the way to the battery. Either way you are grounding directly to the battery.

There are 2 reasons auto installs ground on short runs:

One reason is gound loop: a car can be grounded to the chassis/frame/other locations is because the entire chassis is connected to the charging/electrical system ground. Open your hood and look at the negative lug on you battery and I bet it is tied to the fender or firewall, engine block, and frame. Ground loop is caused by many couple of things, here are two common ones: one is a paramagnetic effect. Anytime current travels through a wire, it creates an electrical field aound it. That interference will creep into non or poorly insulated wiring if it crosses it or if it runs parallel with it. So by grounding on a short run, you remove the chance of creating a loop. The other thing that causes ground loop is having two components seeking ground through a common wire. If you ground two amps close together, the components will try and find ground in the wiring back to the other components. You have heard this as alternator whine (when it has bad diodes) or clicks and pops when adjusting climate control fans. There are other ways to have loop two, but those are the two most common.

The other reason to ground to the chassis is to lower install cost and for current load safety. When calculating wire size for an install, you have to add the total wire length for the entire circuit. This includes power and ground wires. If that distance is far, you may need to go up higher in AWG to safely connect the components to the electrical system. Grounding to a common chassis ground removes this need.

Is it better to wire my battery bank in series or parallel? Does it matter?

That depends on the output you want the batteries to have as far as voltage. If you wire 2 batteries in series, they will output 24 volts, and you will likely cook some stuff. Wire them in parallel and you will remain at 12V with a combined AH and CCA from the batteries in it.

[dogbert]

Some older vintage and British cars had a positive grounding system, but it was in the wiring only.

...and, given their stellar track record on wiring, I'd say that pretty much rules this out as an option