Battery Cable Fusing

[GordMay]

Originally Posted by missourisailor

Even though the PVC tube is the gray electrical conduit used in commercial applications...it is still plastic!
So it still melts and burns.
It was installed mostly for abrasion protection.

PVC products (conduit) will burn when exposed to a fire.
PVC products, however, are self-extinguishing, i.e. if the ignition source is withdrawn they will stop burning.

Because of its high chlorine content PVC products have fire resistant characteristics, which are quite favourable as:
they are difficult to ignite,
heat production is comparatively low,
and they tend to char rather than generate flaming droplets.

[Maine Sail]

This would be an ABYC "complaint" installation.

[john61ct]

What about the fusing vs imbalance issue?

[Maine Sail]

Originally Posted by john61ct

What about the fusing vs imbalance issue?

The take offs are at opposite ends of the bank helping to minimize imbalance issues. Everything on a boat is a compromise, a port starboard house bank is just one of them. You just do the best you can. With six batteries in parallel, and no fusing, there will still be some level of imbalance as batteries can still vary, even when purchased from the same lot. All we can do is try to minimize balance issues and build a safe installation.

[john61ct]

Completely agree.

Therefore adding unnecessary fuses for "balancing resistance" on the negative side would not be worthwhile.

[Zil]

Does the size of the cables count? OP has 4/0 at 48 inch. I use Maine Sail diagram for connections. Need a healthy fuse. I wouldn't use a MRBF with 4/0 cable. But agree each of the three positives need be fused.

[Frankly]

Would not argue about keeping a balanced configuration on a large commercial battery backup system where there is almost no wiring penalty. My point is on a typical small yacht there are so many other variables/ compromises that creep in (fuse/ switch/ connection/ wiring resistance) that to go out of ones way to try to balance the wiring is probably not money well spent.

One thing often overlooked along the lines of protecting primary conductors with a sheath or conduit. By physically separating the positive conductor from the negative conductor/ any ground surface so that a short circuit/ ground fault is impossible, the system is then intrinsically safe. Overloads can only occur in association with the load and as long as the circuit overload protection is ahead of the load then all is well. We typically place the circuit protection closest to the source because we kill two birds with one stone. But not the only way to skin the cat.

[Cyrus Safdari]

Originally Posted by Maine Sail

This would be an ABYC "complaint" installation.

A better version would maintain balanced charges for all the batteries by using an "S" figure wiring for the + and - cable, there's a picture somehwere on the web

[missourisailor]

Thanks to all who took the time to respond.
When I started this thread, I pretty much knew the answer before asking the question.

I was just hoping that some how/some where in the ABYC std’s I over looked the section pertaining to connecting batteries in two locations.
It appears that I did not.

With my experience with land based storage facilities, I knew that balance circuits were optimal. And pretty much the norm..
What I do not know is how this scales DOWN to our mobile banks.

As Frank and Mainesail has pointed out, I think that I’m making a big to-do out of nothing.

With only 12 or so inches of the interconnect cable outside of a battery compartment (this 12" is what is in the conduit), I’m pretty comfortable with the interconnect being unfused.

But Murphy has a bad nack of derailing the best laid plans.
So to be on the safe side, I’m going to fuse both ends of the pos. interconnect cable. And if need be, I’ll simply swap the batteries around once a year, to maintain some sense of balance.

[missourisailor]

Originally Posted by Cyrus Safdari

A better version would maintain balanced charges for all the batteries by using an "S" figure wiring for the + and - cable, there's a picture somehwere on the web

Cyrus,
I'm sorry but I can not visualize the connection plan that you are describing.

I don't know what you mean by "S" configuration.


Please elaborate.

[john61ct]

Once MS has given the answer better to just stick with that.

[Cyrus Safdari]

Originally Posted by missourisailor

Cyrus,
I'm sorry but I can not visualize the connection plan that you are describing.

I don't know what you mean by "S" configuration.


Please elaborate.

This page explains it, there are others
https://www.impactbattery.com/blog/t...s-in-parallel/

[john61ct]

This is Gibbo's page on the topic, canonical afaik

http://www.smartgauge.co.uk/batt_con.html

But the variations don't handle the fact that half the bank is a distance from the other half, and it is important to minimize the number of over-long wire segments.

MS' use of the #2 pattern afaict is the optimal balance.

[Zil]

Originally Posted by john61ct

Once MS has given the answer better to just stick with that.

Yes. He may do an article and use you for the "bad example"

[missourisailor]

Originally Posted by Cyrus Safdari

This page explains it, there are others

Cyrus
Thanks for the explanation.


But if you place batteries "A" & "B" in a separate compartment from batteries "C" & "D" you still have the problem of how to protect the long interconnect cable from pos "A" to pos "C". Which is the problem that I'm trying to resolve.


Additionally, thanks for the link.
I have not ran across the "impactbattery.com" site.