1. The CFRs don't specifically exempt battery or cell interconnections.
The trouble is that when these regs were written, battery installations were different thant they often are today.
So the regs lag reality. And unfortunately, it takes an act of congress (literally) to change the CFRs.
I expect that the ABYC will create standards dealing with large battery bank installations soon, and eventually the CFRs will amended to include their rcommendations.
2. The CFRs do not prohibit installing overcurrent protection on the grounded conductor, but they require it on the ungrounded conductor.
3. Starter circuits (and some others) are exempt from overcurrent protection requirements. Perhaps at the time the CFR was written, suitable protection devices were not available?
This is all in this group's files, look for "USCG Electrical"
-Tom
--- In electricboats@yahoogroups.com, John Acord <jcacord@...> wrote:
>
> Tom,
>
> If the CFR requires:
>
> "Each ungrounded current-carrying conductor must be protected by a manually
> reset, tripfree circuit breaker or fuse."
>
> does that mean that in a series string of batteries where the first battery
> is "grounded" that a fuse is required in the "ungrounded" current-carrying
> conductor between each successive battery along the string? The wording
> would seem to imply such! On the other hand one could argue that there
> being no paths for the current other than through the entire string of
> batteries that the "ungrounded" current carrying conductors of the battery
> stack, including the most positive conductor exiting the stack, are in fact
> protected by a fuse where that fuse is connected to the most negative
> terminal of the stack.
>
> Does the CFR "prohibit" having a fuse in both the positive side and the
> negative side of a current carrying conductor?
>
> I'm not trying to nit pick but just want to think about things. In a
> battery stack where they are, in normal usage, operating as a single entity
> with no branch circuits within, then whether the fuse is in the positive
> side of the stack or the negative side of the stack, over current
> protection is intact for the string.
>
> In addition, since things near or in the surrounding area of the batteries
> might normally be "grounded" then a fuse in the positive side does not
> protect from "grounding" an intermediate terminal in the series string.
> Such an incident could occur during periodic inspection of the batteries.
>
> Keep in mind this is all in the perspective of the procedure (right or
> wrong) of working on a connection in the battery stack which started this
> sequence of discussion.
>
> Sometimes rules and common practices are not adequate. I don't know if the
> practice has been changed but one finds starter circuits on ICE's where the
> starter motor is connected directly to the battery without over current
> protection. I had a friend almost loose a boat due to a fire caused by
> abrasion and subsequent grounding of the 2/0 conductor to the starter.
> When that happened they had no way to shut off the current as the battery
> was located in the area of the fire and there was no way to disconnect it.
> (My boat has a fuse and a disconnect switch in the starter battery
> circuit!)
>
> My hopes are that electric boat installations look at all these things as
> well.
>
> John
> --
> Flatwater Electronics
> www.flatwaterfarm.com
> "Neurosurgery for computer looms."
>
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