Electrical Bonding Question?

[Pickles]

I am going to rewire my boat, and I have a question concerning electrical bonding. I have an aluminum boat and I know that you should not attach grounds to the hull, but to the battery itself. I know the engine is grounded to the battery through the starter. My question is should I or should I not ground the hull to the battery as well? I have heard both sides of the coin on this one, and would like a definitive answer? :help:

[Boatdog]

Chris,

Yes.

TC

:)

[chucks electric]

yes you should this cancells out transient voltage. the bonding should be the same size as the negative cable. use a 4 stud buss strip and connect all battery grounds and engine ground to this piece. also add accessorie ground busses tie these together with a 4ga wire. also make sure that your manifolds and fuel tank are all grounded together. i recommend and use blue sea components. there is so much info needed to do this properly. there is a book written by nigel calder, cant remember the name but it can be found by the authors name but i hope this information helps.

[lurking_out_loud]

In my experience the correct answer is NO. By bonding your hull to your battery you are turning your entire boat into a grounding anode. This will create a "HOT BOAT" situation which will effectively shut down your ability to catch fish.

-LOL

[Boatdog]

As you said earlier, Pickles, you have heard arguments both ways. Here is one report on why I said yes. I'll find more.

METAL BOATS

Potential corrosion

Owners of metal vessels must forestall electrochemical damage

by Nigel Calder
Ocean Navigator NO. 63
September/October 1994

"So far as the DC system is concerned, the power source is the boat's batteries, and the path back to the battery consists of the various ground wires to appliances. These ground wires have to be designed and installed to minimize any resistance in the ground circuit. This comes down to using marine-quality wiring (tinned), properly sized for the job (a maximum 3% voltage drop at full load in most applications), fitted with marine-quality terminals. Beyond this, cables should be run in such a manner as to keep them out of damp areas of the boat and protected at all points where chafe might create a risk of a short to the hull of the boat. Finally, if the hull is properly bonded, the bonding system will provide a low-resistance path back to the battery negative so that in the event of a leak to the hull, the leak will be recovered' and lead directly back to the battery, rather than finding a path to ground through the water. (It is interesting to note that, in the case of the boat mentioned at the beginning of this article, the combination of the use of the hull as a ground path and an inadequately bonded hull, caused the current to be radiated into the water to the propeller and so up the shaft to a grounded engine block. Severe corrosion ensued where the current was fed into the water.)"

[Boatdog]

This from
Marine Electrical Check List

A Guide to Inspecting Marine Electrical Systems
This document is available on the Internet at www.islandnet.com/robb/marine.html (http://www.islandnet.com/robb/marine.html) and it is shareware (http://www.islandnet.com/robb/marine.html#Shareware).
copyright © Robb Zuk. All rights reserved.

Bonding and Lightning Protection

Four reasons for a bonding system are:

Electrically connect metal fittings for corrosion protection systems.
Protect metal fittings from stray currents originating on board.
Reduce electronic interference (noise) for LORAN and radios.
Provide a safe path for lightning strikes and the high voltages induced in metal objects by a lightning strikedoes not normally carry current (except for corrosion protection current)

Do not use the bonding system in place of negative power wires (i.e., as a 'ground return') or stray current corrosion problems can result.
the 'main bonding conductor' runs near the centre line of the ship and connects to the Common Ground Point (http://www.islandnet.com/robb/marine.html#CommonGroundPoint) -- all other bonding conductors connect to the main bonding conductor or directly to the Common Ground Point

Running bonding conductors from one fitting to another increases the risk of shock and corrosion damage if stray currents run through the bonding system. Each bonded fitting should have only one connection point and one wire running to it.
bonding system connects with DC power system at Common Ground Point only (test)


Common Ground Point (ship's ground)

grounds from batteries, engine, switch-panel negative bus bar, bonding system, auxiliary power generator, underwater ground plate, ship's 120 Volt (http://www.islandnet.com/robb/marine.html#ACSystem) safety-ground, and LORAN signal ground all meet at one point

This point must be a heavy bus bar or bracket with bolted connections.

Note: When referring to 12 Volt wiring, 'ground', 'negative' and 'ground return' are all equivalent terms.
easy to access and located as far above bilge levels as practicable
labelled as Common Ground Point

[chucks electric]

that was well presented and explained. i should have done a better job explaining thanks for the effort!:bowdown:

[Pickles]

Thanks Boatdog for the in-depth information! :cheers: