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Negative ground buss opinions

Old 10-06-2014, 07:28 AM
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Default Negative ground buss opinions

Background: I am going to perform some clean up of the wiring in console.The boat is wired for 12V and I have 3 batteries. Configuration as follows:

One 8D for house.

Two Group 27 for starting/engines.

Each battery has its own battery switch. House isolated from starting batteries. Other 2 switches for starting can be started from either battery on switch selector.

Onboard battery charger with leg for each battery to charge independently.

Have one common negative buss w/ negative from each battery going to buss.

Question: I have seen this done on other projects and was not sure if I need to run wires from each battery negative to each other in addition to the negative buss or leave as is?
Old 10-06-2014, 08:14 AM
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Hello. Just one thign I would be sure of, the negative buss bar has the ability to handle the amperage that could be put through it. In theory I can´t see a problem with this set up. Hope this helps.
Old 10-06-2014, 08:14 AM
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Originally Posted by 1love View Post
Background: I am going to perform some clean up of the wiring in console.The boat is wired for 12V and I have 3 batteries. Configuration as follows:

One 8D for house.

Two Group 27 for starting/engines.

Each battery has its own battery switch. House isolated from starting batteries. Other 2 switches for starting can be started from either battery on switch selector.

Onboard battery charger with leg for each battery to charge independently.

Have one common negative buss w/ negative from each battery going to buss.

Question: I have seen this done on other projects and was not sure if I need to run wires from each battery negative to each other in addition to the negative buss or leave as is?
As long as your negative leads are high quality low gauge wires and the buss bar can handle the current, I would just leave it that way.
Old 10-06-2014, 08:50 AM
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Thank you for the quick replies buxa and stiletto.

Buxa, are you saying you do not see a problem w/ the way it currently is (i.e. each battery negative to the buss), or that I should tie each battery negative together in addition to each attaching to the buss bar?

The buss bar is Blue Sea 150ADC continuous w/ 1/4"-20 studs.
Old 10-06-2014, 08:59 AM
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A lot will also depend on the grounds to the starters on the engines, if they connect directly to their respective batteries they will provide return for cranking from them but if you ever have to use the house to start an engine, that 150 amp buss bar can be overloaded. If the starter ground all connect to this 150A buss bar also it needs to be upgraded to handle more current to be on the safe side.
Old 10-06-2014, 09:34 AM
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Originally Posted by bills106 View Post
A lot will also depend on the grounds to the starters on the engines, if they connect directly to their respective batteries they will provide return for cranking from them but if you ever have to use the house to start an engine, that 150 amp buss bar can be overloaded. If the starter ground all connect to this 150A buss bar also it needs to be upgraded to handle more current to be on the safe side.
Thank you Bill. I actually have the ability to add another 150amp buss. Do you recommend that I tie them together w/ jumpers or just upgrade to a larger amperage buss (i.e. 600 amp)?
Old 10-06-2014, 01:02 PM
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Here is what I found after Bills last post. Bill was spot on w/ his reply, as my amp requirement per engine is around 150 each, thus totaling approximately 300 amps. My "max" total amp draw on my house is approximately 125 amps. So, this puts me at 425 or so amps and will likely require the 600 amp buss and I will size the appropriate cable for the amp draw for the length required. Any other input or rationale is welcome.
Old 10-06-2014, 04:53 PM
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To be able to start on any of the battery banks I would connect all the battery negative leads together at the batteries, by taking them all to the buss bar you lengthen the total cable length to the engine starters, and create a voltage drop from the battery negative leads to the buss bar when starting. This voltage drop will affect your electronics at engine start if their negative leads are connected to the buss bar.

Use the negative buss bar for all house and lighting loads.

JMO

Jim

Last edited by jfwireless; 10-06-2014 at 05:25 PM.
Old 10-06-2014, 08:09 PM
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Banks should be wired to a bus, not each other. This is proper form. Yours is good as long as the wire and bus is approite size

Batteries in a bank get wired post to post.

Run engines and house loads to bus. Each battery should only have one connection

The buss should be near the batteries.
Old 10-07-2014, 04:34 AM
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Hello again. I agree with all the posts here, I like to wire to the Buss myself, common negative ground, especially if you would need to use another (house) battery for emergency start via a battery switch. I have also seen the batteries negatives tied together at the battery posts, it depends on the layout of the batteries themselves and which option is easier. I try to avoid stacking terminals at the battery posts, but as said in another post, check the buss bar rating and size your battery cables accordingly to avoid voltage drop. Hope this helps.
Old 10-07-2014, 05:35 AM
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Thank you everyone for the feedback. It sounds like I have many options provided the buss and cable are sized appropriate, which is good. So, I am leaning towards doing both, meaning connecting the negative posts together on all batteries, and connecting them to a common negative buss. May be overkill, but logic tells me this will minimize any electrical gremlins from the ground aspect.
Old 10-07-2014, 07:10 AM
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Default Negative battery connection

I would love to see some pics or diagram of how it should be done
Old 10-07-2014, 07:30 AM
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Originally Posted by aln2202 View Post
I would love to see some pics or diagram of how it should be done
These are the pics which gave me the idea once I decided to tackle this. Note that the negative posts are tied together in 1st pic and 2nd pic shows how they all go back to a common buss. pics on pages 21-22 and link found here http://www.thehulltruth.com/boating-...extension.html
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Old 10-07-2014, 09:02 AM
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That setup is comical. Love the loops lol...

And the triple 2/0 feeding the house neg with a few 14awgs.

Someone bought a whole wire spool and needed to use up the whole thing...

Those battery jumpers should be shortened up so they don't rub on each other
Old 10-07-2014, 10:30 AM
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Originally Posted by smac999 View Post
The triple 2/0 feeding the house neg with a few 14awgs.
My assumption is that this was done to create one common ground for the entire system, not solely to power the house common/neg. If I am not mistaken, the outboard(s) become the ground on an outboard powered boat, thus this would likely minimize any electrical issues as a result of an insufficient ground anywhere in the system, since it is all going back to a common buss. Hence the reason for my post.

This diagram shows similar
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Old 10-08-2014, 08:10 AM
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Originally Posted by smac999 View Post
Banks should be wired to a bus, not each other. This is proper form. Yours is good as long as the wire and bus is approite size

Batteries in a bank get wired post to post.

Run engines and house loads to bus. Each battery should only have one connection

The buss should be near the batteries.
One way for all I guess, but not me.

I prefer not to run starter current through the battery bus and not put voltage drops on this bus for house loads when starting engines or other heavy current draws like windless.

Lead acid batteries are huge capacitors that absorb transients, like when starting an engine or possibly any power issue on the boat. Leaving these loads at the battery buss rather than on the negative battery post can allow transient and ground fault current to flow in the wrong direction. Transients are AC in nature not DC, so its reactance not resistance that is important.

I prefer to have my negative common point on the battery negative leads themselves. This does not add any more cables than running all the battery negative leads to the negative battery buss.

Again, just my opinion and respect all others as well.

Jim

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