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**RDOIII** · 01-30-2012, 06:02 PM

I am not sure of the issue on grounding. I have commoned everything to the engine grounds and have not had a problem.

One other comment on the wiring is I am not sure if it is stock but it appears that the two alternators are connected to their respective start batteries. The house then gets a charge when combined with the start battery through the respective CR. The problem with this is the voltage that the alternator will see is the combined start and house battery. The resultant charge will be greatly diminished. I would consider placing the output of both alternators on the house battery and then combine to the starts. The house bank will charge considerably faster and when nearly charged will be connected to top of the start batteries.

**Guest** · 03-10-2012, 09:31 AM

Hi all, just bumping this thread for any comments and opinions, especially from the electric guru's.

Many thanks

Rick

**ksanders** · 03-10-2012, 10:34 AM

Rick

To answer your original question, the shunt is as you've indicated in series with the negative lead on the house battery. The easiest way to do this physically is to run a 4/0 cable from the battery negatice post to the shunt, then from the shunt to a buss bar where any other negative cables connect.

On the positive side, the connection should include a separate disconnect switch for the inverter, and not utilize or rely on the house disconnect. Also remember that you need a fuse on the positive lead of the house battery. The way I like to do this is to use a battery post style fuse, then a 4/0 cable feeding a buss bar. This makes interconnection of new systems easy.

**JimMc** · 03-10-2012, 05:08 PM

I can not address all the questions you seem to ask.

I can say in general you are correct in that the shunt should be the last and sole path to the House Battery Negative.

My labels are a bit hard to see but the shunt is in the middle right connecting to the bottom of the vertical buss. The cable leads from the shunt to the house battery negative.

**ksanders** · 03-10-2012, 06:06 PM

JimMc wrote:
I can not address all the questions you seem to ask.

I can say in general you are correct in that the shunt should be the last and sole path to the House Battery Negative.

My labels are a bit hard to see but the shunt is in the middle right connecting to the bottom of the vertical buss. The cable leads from the shunt to the house battery negative.

Yes, thats exactly how I described it. Battery->shunt->buss bar.

Great installation!

**Guest** · 03-10-2012, 10:00 PM

Thx for the replies guys. Since I first posted, I have set up according to the small attached schematic, and as you have both recommended.

Great installation Jim

Cheers

Rick

**2850Bounty** · 03-11-2012, 06:33 AM

I'm chiming in very late on this.... forgive my redundancy if so.

ricks3988 wrote:

Hello all, I am hoping for comments / opinions on the most correct way to layout negative cabling for an inverter charger / smart shunt on my 2001 3988. I have added an alternate layout option hoping for opinion on which is better, or if either layout is fine.

[COLOR]"#0000FF" wrote:
Double check me on this, but if Xantrex (or similar) the main Pos cable should make a direct House Bank Batt Connection (fused).... IOW, do not allow an MBSS path!

However, the Negative must pass through the shunt upon it's return to the battery bank being monitored.

If the Inverter Negative uses the "system negative common", it can't help but do this! [/COLOR]

I believe the feedback re alternators could be connected to house bank and then combined to start banks is possibly a good idea, although with stock alternators I would worry about them over working (heating). The boat is equipped with an 8kw gen, so the current layout helps a bit toward charging house while running, but house is mostly charged by generator.

[COLOR]"#0000FF" wrote:
Talk to Jim McNeely about the use of ACR's and/or VSR's for this.[/COLOR]

I have read extensively on the forum and the vault section (re shunts) as well as my Nigel Calder manual, and inverter install manual, but I still come away with some uncertainty. I have attached a portion of the modified electric schematic. I have drawn in the Inverter / Charger and smart shunt as well as two Charge Relays (combiners). I have placed the I/C and shunt into the electric layout as designed by Bayliner. From house bank DC negative to shunt (batt. side) and then I/C into shunt (load side) with DC negative to the Engine Block 'system common' and from there to the Main DC Buss Ground.

On some of the Vault thread layouts; The house bank DC negative would go to shunt (batt. side) and then I/C into shunt (load side) with DC negative running to the Main DC Buss Ground, and a separate cable from the Engine Block 'system common' to the Main DC Buss Ground as illustrated in the additional layout.

I am unsure if the way I have drawn this makes the engine block 'system common' current carrying?

[COLOR]"#0000FF" wrote:
Rick....., some of the Xantrex schematics are confusing in that they show one terminal of the shunt being used for a termination point only.

If you'll notice, this connection does not allow current to pass "through" the shunt unless the source is the battery bank being monitored.

It's simply using this stud as a termination point, and I assure you that this is a System Negative Common.

This is perhaps where the "to" -vs- "through" the shunt has been confusing to some.

I wish that they'd NOT show it this way! [/COLOR]

The inverter company recommends the Chassis ground should connect to the engine block 'system common'. This brings me to questions regarding non current carrying DC ground, DC negative buss, and AC ground buss. Should a 12V non current carrying Chassis ground (for any 12V appliance/electronics) connect to the current carrying Main DC Buss Ground (that is the DC negative buss) or the non current carrying AC ground buss where all AC appliance grounds connect as well as the bonding conductor, and then a single cable connects this to the Main DC Buss Ground.

Any clarity will be greatly appreciated.

[COLOR]"#0000FF" wrote:
That is a great question, but easily answered if you think in terms of ALL Negatives using the "System Negtaive Common".... I.E., Engine Block.

When done this way, and when the shunt is installed correctly, any and all negative current as a result of HLBB power, has no choice but to pass through the shunt resistor. [/COLOR]

ksanders wrote:
Rick, To answer your original question, the shunt is as you've indicated in series with the negative lead on the house battery. The easiest way to do this physically is to run a 4/0 cable from the battery negative post to the shunt, then from the shunt to a buss bar where any other negative cables connect.

I'd personally take the Shunt's negative directly to the engine block (aka "system negative common"), and then feed a buss bar from the engine if needed......, but your method will certainly work.

JimMc wrote:
I can say in general you are correct in that the shunt should be the last and sole path to the House Battery Negative.

Yep! This has been an area of some confusion here for quite a while, and is what prompted me to write up the Vault page on this topic.

Rick, I also agree with Jim, Kevin, RDOIII and the inverter company's recommendation for the Negative connecting to the engine block 'system negative common'.

I like the term "system negative common".

This is where our starter motor and alternator heavy loads receive their initial path to Negative, so it only makes sense that all other Negatives use the same path.

Or IOW's, use an engine termination point as a "Home Base", so to speak.

Then if we need a remote Negative "buss"..., that also can connect to the "system neg common".

Here are two schematics. They have each been touched up by me.

One (and as per how some Xantrex schematics have shown this) has lead people to misunderstanding the Shunt configuration,

It has become confusing by showing one of the shunt terminals being used to terminate two negative, but separate, battery bank cables.

In either of these schematics, they could just as easily have shown the Start Batt making it's own System Negative Common connection..... completely avoiding the use of the shunt terminal.

.

Attached files http://baylinerownersclub.org/media/...mage.jpg[/img] http://baylinerownersclub.org/media/...mage.jpg[/img]

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Inverter DC cable layout on 3988-gctid348418

Inverter DC cable layout on 3988-gctid348418

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