Grounding an Amplifier

J.unio.R · Outlaw Joined: 23 Feb 2009 Posts: 154 City: E-City, NC

Im installing an amp in my boat and I would like to know where can I put the ground wire? The manual says to keep it 3 ft or closer to the amp but I have heard that you ground it near the battery which is farther than 3 ft from my amp Question

. Any info would be appreciated. Thanks.

gx205 · Outlaw Joined: 23 May 2007 Posts: 118

I was told to run my ground wire, and positive wire all the way back to your battery. If you install a second amp, you can jump your positive off of the first amp, but it still is best to run all amp grounds back to the battery.

Hope this helps

J.unio.R · Outlaw Joined: 23 Feb 2009 Posts: 154 City: E-City, NC

Yeah thats what Im going to do. Thanks.

Brit Rider · Posted: Mar 07, 2009 5:43 am Post subject:

gx205, Not necessarily true unless using a distribution block and doing the figures on wire gauge.

J.unio.R, You will need to run all ground wires to the battery. What amp is it? We can do the maths and work out what size wire you will need in order for this to be safe. You also need to fuse the amp; this DOES need to be within 18" of the battery.

gx205 · Outlaw Joined: 23 May 2007 Posts: 118

Brit Rider, I guess I did forget to mention the distribution block.

I have three amps on my boat, one for the subwoofer, one for the boat speakers, and one for the tower speakers. I ran two main positve cables from my battery switch, to a distribution block, and then jump three positive cables to each amp(one per amp).

My local stereo guy told me, that it was alright to share positve feeds to amps, but he highly recommended running ALL negative ground cables from each amp, all the way back to the battery on a boat, since it's hard to get a true ground.

So far this setup has worked fine for me.

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

Not to threadjack here, but I'm looking to install my deck and one amp for right now. I will have two batteries with a selector switch. My amp and stereo will be up front and the batteries will be right near them. Should I do a distribution block of some sort or just wire striaght to the batteries. My plan is to run the stereo off whichever battery is "selected" at the time, so I can run off the "engine" battery while the engine is running and a deep cycle battery when we are parked.

J.unio.R · Outlaw Joined: 23 Feb 2009 Posts: 154 City: E-City, NC

I am running a 1200 watt SSL amp to four 300 watt SJS Designz speakers. The ground and power cables are 4 gauge with a 60 amp fuse. I finished the install today and everything worked and sounds great.

Now I am really itching to get on the water! Confused

Brit Rider · Posted: Mar 08, 2009 4:32 am Post subject:

Okie Boarder, Sounds like a relatively straight forward setup but I think you need to think about your power a bit more.

The idea of dual batteries is that you have 1 dedicated starting battery. This should be isolated from everything else and just be wired to the essential gear such as engine starter, instruments etc.

The other battery or 'house' battery is for powering the other stuff like stereos.

So what you will want to do is leave the battery you have now, then just add a 2nd via a battery selector switch/combiner and put all your stereo stuff onto this battery.

Then you cna bump your stereo all you want, and once that batts dead, you can switch over to the starter battery and the boat has power to get going and can then charge your batteries back up.

Therefore, in regard to your question, you won't need a distribution block, just a fused power feed from the house battery to the amp and a ground going from the amp to the house battery. In terms of powering you stereo deck you can run wires direct from the house battery, again, just make sure everything's fused and you'll be good to go! Very Happy

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

So, I'm always running the second battery to power the stereo? Hmmm, never thought that was the way it was done. Is it best to go with a deep cycle?

The way I understand the battery switch, it will control which battery is getting an input from the alternator and which outputs to the system, right?

I may be misunderstanding this, so maybe you can set me straight. If you have some sort of wiring diagram, that would be very helpful.

Brit Rider · Posted: Mar 08, 2009 10:56 am Post subject:

Okie Boarder, Kind of, the reason for the second battery is to deal with the ampere requirement of the stereo and to allow a starting battery to be protected at all times.

A battery switch will allow you to 'feed' power to a particular battery, but in practice you'll leave it set to 'both' which wil allow power to be drawn from both batteries, and for the alternator to feed them both. its only when you turn the engine off, and wan to play the stereo for a while that you would switch over to the ancillary battery.

Generally, its more popular these days to go to an auto relay system. this means that when the boat is running, both batteries get charge... then when you turn the engine off, a relay snaps open, which isolates the starting battery from the stereo one. the stereo then draws its power from the extra battery.. come turn-key time, the relay snaps closed and allows all the batteries to crank the engine... this is cheap and reliable. Also, if the relay were to fail, you'd still have a protected starting battery. Cool

Does this make sense?

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

Yup, makes sense. Seems like a lot of work for the set up I'm looking to do. The stereo isn't going to pull much juice, but the amp will pull some. I have an extra deep cycle battery, so I think I'm going to install that and power my amp and sub off it for now, since the stereo wiring is already connected in to the electrical system. I'll just let it run independent and charge it at home instead of trying to connect it into the electrical system. Since I'll run the amp off it and the stereo off the main battery, should I tie the two battery grounds together at the batteries or run a ground from the second battery to the engine?

Brit Rider · Posted: Mar 09, 2009 4:55 am Post subject:

IF you're thinking of doing it that way, to keep things simple... I'd just throw the two batteries together and call it done. that will give you plenty of reserve power.

Just put the new battery next to the other and add a 4 guage cable from the positive of the current battery, to the positive of the new one. and the same on the negative posts.

Your alternator will then charge both and you'll still be able to isolate the power when you use your current isolator key (assuming you add amps and stuff tot he isolator, not the actual pos terminals on the batteries.

This will be easy and straight forward for you Cool

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

Brit Rider · Posted: Mar 09, 2009 7:48 am Post subject:

Okie Boarder, When you leave your boat, don't you have a switch to flick or a key to turn and unplug that isolates the electrical circuit from the batts?

What boat do you have?

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

I have the ignition switch, and also have push button switches for main power and for radio on my dash. It is a 1989 Supra Sunsport.

pet575 · Posted: Mar 09, 2009 11:44 am Post subject:

Okie Boarder, I'm not saying Brit Rider doesn't know what he's talking about but I go with a different setup. I have 2 batteries that are on a switch. I rarely, if ever, use the "Both" selector on the switch. I nearly always use 1 or 2 only, switching between them on different days.

Does this put the burden on me to switch them back and forth? Yes, but it is a lot simpler than wiring up separate batteries, isolaters, etc. I'm aware of the shortcomings of my system, but rarely using "Both" is a good safeguard against those shortcomings. I've never had a situation where I've killed 2 batteries on the water because I used the "Both" selector on my battery.

Just an alternative method that is simpler to install...

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

pet575, so do you just have two batterys and the selector switch and you alternate between them?

Are they both "Marine Starting" or "Deep Cycle" or one of each?

At this point I might do the selector, but I'm thinking just to put the deep cycle in there and run the amp for the sub off it. Everything else would just stay running off the normal battery wired into the boat's electrical system. Then, when the deep cycle needs charging I'd just hook my charger to it at home.

If I went without the selector, running the amp only off the deep cycle, should I tie the deep cycle's ground to the other battery ground or to the motor ground?

pet575 · Posted: Mar 09, 2009 12:41 pm Post subject:

Yes. Both are combo starting/deep cycle batteries.

Only downside to your "I might" proposal is that if (for whatever reason) the deep cycle dies on the water then you are without tunes until you can get that charger hooked back up for a few hours. The benefit of hooking it into your boat's system is the alternator's ability to recharge the batteries on the water.

I don't see any need to ground them separately if you went without the selector.

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

Ahhhh, OK. I have the one "starting" and one "deep cycle". I'm concerned about an imbalance with the way they work as far as both being charged at the same time.

Actually, I'd run the deck and 4 main speakers off the main battery tied into the electrical system, so I'd only lose my sub if the battery went dead.

pet575 · Posted: Mar 09, 2009 1:38 pm Post subject:

Many people use that setup with the thought that the deep cycle handles the prolonged draw better, relying on the starting battery to keep separate. A good and simple setup. Might be a bit risky running deck off of one and amp off the other if you lose track of time. Just something to think about with that kind of setup.

I'm no electrician, but I don't see why using the same ground is a problem. Are you thinking there is the potential that a dead starting battery would drain the deep cycle if they share a common ground?

Okie Boarder · Ladies Man Joined: 03 Mar 2008 Posts: 10056 City: Edmond

Nope, I'm thinking more of preventing a floating ground situation and picking up ignition noise in the sound system. Yeah, I'll have to think about how I want to do it, in the end. Maybe it is better to have the whole audio system on the deep cycle...I dunno.

Brit Rider · Posted: Mar 09, 2009 2:45 pm Post subject:

Seems to me like this is getting complicated, in order to keep things simple...pet575, you definitely raise a fair way of doing it and I agree that your way is another option.

Okie Boarder, At the end of the day, There's probably 10 different ways to do this, you'll have to find the solution that best works for you...

Personally, I'd just do it properly the first time (Auto-switching relay system with 2 isolated batteries, as I described first) rather than trying to save time by doing half a job or 'making do'... the more I think about it the more i think that by 'keeping it simple' the more chance of problem there could be later on and time/money savings are minimal.

m_lesney · Soul Rider Joined: 22 Feb 2008 Posts: 358 City: Austin

Ive got two batts and all the wires to the boat are ran to the perko switch so its no half on one half on the other and it works great!! Wink