House bank negitive to start bank negitive

[Bowdrie]

Originally Posted by S/V Illusion

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

Define "Completely" in the context used.

[noelex 77]

Originally Posted by S/V Illusion

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

With double pole switches and circuit breakers why is it impossible to isolate the DC negative?

[team karst]

Originally Posted by Bowdrie

Define "Completely" in the context used.

Easy. If/when lightning hits the boat, surviving wiring and devices were isolated. [emoji1362]
That test would take measures beyond multimeter readings.

[Bowdrie]

Originally Posted by team karst

Easy. If/when lightning hits the boat, surviving wiring and devices were isolated. [emoji1362]
That test would take measures beyond multimeter readings.

Haha, you got a point.
Lightning is always the raging bull in the China Shop, damage may be mitigated, but it's a toss of the coin.

[s/v Jedi]

Originally Posted by boatpoker

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

In Dutch college taught as being the KNAP rule (knap means handsome or smart in Dutch), standing for Kathode Negatief, Anode Positief.

Wonder if other countries have similar tricks to remember

[s/v Jedi]

Originally Posted by S/V Illusion

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

And yet, this is what the OP has.

I also have a completely galvanically isolated battery for electronics.

[S/V Illusion]

Originally Posted by s/v Jedi

And yet, this is what the OP has.

I also have a completely galvanically isolated battery for electronics.

Not worth debating but suffice it to say almost everything on a boat is interconnected via the water, mast ground, water tank pumps, potable water tanks, shore power connections, lightning ground, radar dome, VHF wiring, ….. so as a practical matter, it’s naïve to suggest something is isolated even when it’s attempted.

[s/v Jedi]

Originally Posted by S/V Illusion

Not worth debating but suffice it to say almost everything on a boat is interconnected via the water, mast ground, water tank pumps, potable water tanks, shore power connections, lightning ground, radar dome, VHF wiring, ….. so as a practical matter, it’s naïve to suggest something is isolated even when it’s attempted.

No, it is isolated. Galvanically isolated. That is a specific term for how it is and you can test the isolation. For example, the Victron isolated dc-dc converter is isolated up to 200V DC which is high enough for everything except a lightning strike (which is why there is a battery as well… so that the dc-dc converter can be disconnected to remove that weak link)

All the examples you state are in play for common house battery and start battery environments. None of that is in play with an isolated battery because it wouldn’t be isolated if it was

[SailingHarmonie]

Originally Posted by S/V Illusion

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

Nonsense. If, for example, you have an aluminum boat you damn well better have isolated grounds, or you WILL have major issues with stray current corrosion (not “electrolysis”) There are advantages to doing it with FRP boats as well, although it is admittedly less critical.

Your EE degree means squat when it come to boat wiring.

[deblen]

Isn't the discussion about corrosion? https://www.corrosionpedia.com/defin...ytic-corrosion

[skenn_ie]

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?

As with so many things: It depends., mostly on whether the DC-DC charger is isolated or has a common negative or, very occasionally, common positive. If it is common negative, the 2 negatives are already connected, albeit with a low-current connection within the charger.. In that case, DO connect both battery negatives to the same place.