House bank negitive to start bank negitive

[motion30]

My house bank is completely isolated from the start battery bank except for a dc-dc charger. So my question is. Should the negitive terminals of the buss bars be connected?

[Bowdrie]

Originally Posted by motion30

My house bank is completely isolated from the start battery bank except for a dc-dc charger. So my question is. Should the negitive terminals of the buss bars be connected?

Are the Neg. of each bank fastened to the engine?
If so, they are already connected together.
Generally good practice is to keep grounds separate in separate systems and then connect them together at only one place, some kind of Main Ground Bus that gathers everything together, so to speak, and connect that to the engine with one big cable.
The Neg cable from the start batt should always connect directly to the engine, (close to the starter,) without any additional terminals/bus bars/claptrap interrupting its run.

[s/v Jedi]

Originally Posted by motion30

My house bank is completely isolated from the start battery bank except for a dc-dc charger. So my question is. Should the negitive terminals of the buss bars be connected?

Have you verified this with a multimeter?

[smac999]

I guess you don’t have an emergency Parellel switch then. Because that would require the grounds to be connected.

But yes. For that and other reasons. The neg of all battery banks on board should be common.

[Bowdrie]

Originally Posted by motion30

My house bank is completely isolated from the start battery bank except for a dc-dc charger.

Originally Posted by smac999

The neg of all battery banks on board should be common.

Not necessarily, the OP speaks of the house bank "completely" isolated from the start bank.
If you want true/real isolation of start/house banks you go to a dual alternator arrangement in which the house alternator and the house batts have zero electrical connection to the engine, or anything that deals with the engine.
You have the engine/gages/preheat/start/electric fuel pump, (if used,) existing in their own little world with zero connections to the outside world of the ship and its house systems, or, (because of a "Drivesaver",) to the outside world of the water.
In this pic you'll see the big Leese-Neville that runs the house batts/loads and the small engine mounted alternator whose only job is to charge the engine starting batts and run the gages/preheat/fuel pump.
Never the twain shall meet.
As a side note, a remote oil filter with a drip pan under it is so much better than some little can screwed onto the engine,

[S/V Illusion]

Originally Posted by motion30

My house bank is completely isolated from the start battery bank except for a dc-dc charger. So my question is. Should the negitive terminals of the buss bars be connected?

It’s “negative” but to answer your question, yes, they could all go to a common ground for various reasons regarding electrolysis not worth describing unless you are interested in the ‘why’.

[motion30]

Originally Posted by s/v Jedi

Have you verified this with a multimeter?

Actually no, but after spending a week rewiring it all. I am confident in what I did

[s/v Jedi]

Originally Posted by motion30

Actually no, but after spending a week rewiring it all. I am confident in what I did

Okay, do check it though… it’s hard to keep things isolated.

You can ignore the naysayers talking about galvanic corrosion. A house battery and associated wiring isolated from boat ground and other batteries is by far the best method for preventing galvanic corrosion. It is like having a cellphone in your pocket: that can’t corrode your boat either

For emergency start you can simply use jump start cables like used for cars.

[boatpoker]

Originally Posted by S/V Illusion

It’s “negative” but to answer your question, yes, they could all go to a common ground for various reasons regarding electrolysis not worth describing unless you are interested in the ‘why’.

"Electrolysis" is an induced process found in industry and laboratories in which the anode is positive and the cathode is negative whereas on your boat it’s the anode that is negative and the cathode which is positive … it simply cannot occur on a boat.

[S/V Illusion]

Originally Posted by boatpoker

"Electrolysis" is an induced process found in industry and laboratories in which the anode is positive and the cathode is negative whereas on your boat it’s the anode that is negative and the cathode which is positive … it simply cannot occur on a boat.

Nonsense. Semantics aside, the effect is the same to boat metals and can be caused by, among other things, multiple ground (negative) loops. Word games serve no purpose here.

[s/v Jedi]

Originally Posted by S/V Illusion

Nonsense. Semantics aside, the effect is the same to boat metals and can be caused by, among other things, multiple ground (negative) loops. Word games serve no purpose here.

Nonsense. With an isolated system, and no ground at all, there is no loops let alone ground loops.

The OP has an isolated house battery.

[boatpoker]

Originally Posted by S/V Illusion

Nonsense. Semantics aside, the effect is the same to boat metals and can be caused by, among other things, multiple ground (negative) loops. Word games serve no purpose here.

If one does not understand the difference between "electrolysis", "stray current" and "galvanic corrosion" the all your electrical advice is questionable.

[S/V Illusion]

Originally Posted by s/v Jedi

Nonsense. With an isolated system, and no ground at all, there is no loops let alone ground loops.

The OP has an isolated house battery.

As a practical matter on a boat, there is no such thing as completely isolated.

[S/V Illusion]

Originally Posted by boatpoker

If one does not understand the difference between "electrolysis", "stray current" and "galvanic corrosion" the all your electrical advice is questionable.

I’m an electrical engineer with 40 years experience. You?

[boatpoker]

Originally Posted by S/V Illusion

I’m an electrical engineer with 40 years experience. You?

Then surely you know that in electrolysis the cathode is negative and the anode is positive and cannot happen on boat.