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Author Topic:   Using battery as bus bar?
pcrussell50 posted 12-28-2012 01:39 AM ET (US)   Profile for pcrussell50   Send Email to pcrussell50  
In Jim's seminal article on small boat power distribution and wiring:

There is some slight admonition about having more than one item connected to a given battery terminal. Does this mean one besides the motor's leads? Or is it better form to have a robust bus bar for each pole of the battery, and connect the motor's leads to each of respective bus bar, along with each load?

Or is it OK to hook the motor leads to the battery AND one more lead to each bus bar?


jimh posted 12-28-2012 09:47 AM ET (US)     Profile for jimh  Send Email to jimh     
In a perfect world of electrical connections, there would be only one terminal connector under each terminal fastener. In terms of your boat battery, this means the posts for positive and negative would only have one cable connected to them, and that cable would carry the current to a bus bar or some other device for distribution. You would expect to find that sort of installation on a commercial or military vessel.

Even though I am aware of this practice and encourage it, I have to confess that I don't always follow it myself, and on my recreational boat I have more than one terminal connected to the positive and negative posts of my battery. But I don't have a gaggle of terminals connected. Two cables is about the limit, and in most cases one of them is a small diameter conductor for a battery charging unit.

In the article (linked above) I describe the same sort of practice and note that it is not always followed. If a terminal post is used to receive more than one conductor, be certain that the ring terminal connectors are making good connection, and use the appropriate flat washers and lock washers to retain them. And then make sure the retaining nut is tightened securely.

Installation where three, four, or five cables are piled up on the battery posts is not good practice.

Also, be certain that the battery cables are clearly identified for polarity. The positive circuit should be carried on conductors with RED insulation, but if that is not possible, the conductors should be clearly marked with red color vinyl electrical tape. Accidentally connecting the battery to the boat circuits with the polarity reversed is usually a disaster.

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