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Old 12-15-2017, 09:54 PM   #21
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Yes those MRBF are great, also Class-T and ANL all good for high currents, and getting close as possible to the post is A Good Thing.

Only caveat for MRBF, be careful the base of the "other end" is well supported if very heavy gauge wire is required, and the wire itself so as not to bear down with too much weight.

If heavy leverage is applied in any direction on the "outside" end, it can put too much stress on the battery post or bolt area, maybe eventually causing wear or cracking.
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Old 12-15-2017, 10:46 PM   #22
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Originally Posted by tiltrider1 View Post
Post 10 shows the correct way to do things. Don’t over look the fact that all the wiring and terminal connections are symmetrical.
If you upgrade your wiring, the symmetry becomes less critical.

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Ditto...The post by CMS is the way to do it.


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If you use MRBF fuses and have lots of head room, that just might work. Many boats of my size lack the room above the batt bank to allow for that. I added an MRBF fuse to my start battery and had to bend it down to make room for the cover.
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Old 12-16-2017, 12:01 AM   #23
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I have 6 golf cart batteries. Each pair runs a heavy cable to a high-current fusible link. So there are 3 of these fuses. Then the individual pairs are switched by 3 cutoff switches so each pair of two 6-volt batteries can be isolated, and finally two heavy copper buss bars provide a positive and negative buss. These are on the back wall of the electrical panel, the front of which pulls down (hinged) for access. All breakers feed off these two buss bars.

Two group 24 starting batteries have their own fusible link and cutoff switch, and there is a fifth switch that can connect the house bank to the starting bank.
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Old 12-16-2017, 01:05 AM   #24
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Each fuse and switch adds resistance thus voltage drops that can add up quickly.

My preference is minimum necessary for safety, but at least be aware and measure for issues.
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Old 12-16-2017, 05:20 AM   #25
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"have their own fusible link"

Do you carry on board replacements , should a problem arise?

Class T fuses are rated for most wire amperage used on boats , and replacements are easily stored and installed.
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Old 12-16-2017, 10:43 AM   #26
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ABYC states if you use an unsheathed wire, you must have current protection with in 7” inches. You also increase the risk of an accidental short from a dropped tool or part. While you have meet the letter of one rule you have made the situation much less safe.
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Old 12-16-2017, 01:50 PM   #27
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You also increase the risk of an accidental short from a dropped tool or part.

Very good point!
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Old 12-16-2017, 02:25 PM   #28
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I do believe ABYC discusses connections inside a battery box.
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Old 12-16-2017, 08:38 PM   #29
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Keep these busbars as close to the bank as is possible and the positive lead should have over current protection within 7" of the positive terminal.

Ok. So therein lies the problem! According to Bluesea: “In any case, fuses, circuit breakers, and switches should not be installed in battery compartments because of the risk of corrosion coupled with the potential presence of explosive gasses.”

So...how do you realistically achieve this? On the stringer near the battery box?

My over current protections located near the positive bus bar, some distance from the battery box. Currently (pardon the pun) I am not in compliance.

Jim
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Old 12-16-2017, 10:02 PM   #30
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Ok. So therein lies the problem! According to Bluesea: “In any case, fuses, circuit breakers, and switches should not be installed in battery compartments because of the risk of corrosion coupled with the potential presence of explosive gasses.”

So...how do you realistically achieve this? On the stringer near the battery box?

My over current protections located near the positive bus bar, some distance from the battery box. Currently (pardon the pun) I am not in compliance.

Jim
First you get 72” before you need over current protection. That’s plenty of distance to find a good location for a buss bar. At that point you can separate your starter path from your house path. If your circuit breakers are farther than 72” from the battery you can put in a large fuse to protect the house circuit wire. Starter circuit does not need to be fused.
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Old 12-16-2017, 10:51 PM   #31
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"have their own fusible link"

Do you carry on board replacements , should a problem arise?

Class T fuses are rated for most wire amperage used on boats , and replacements are easily stored and installed.
Excellent point. Added to my punch list for bringing this old girl into full readiness.
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Old 12-16-2017, 11:21 PM   #32
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Originally Posted by JDCAVE View Post
Ok. So therein lies the problem! According to Bluesea: “In any case, fuses, circuit breakers, and switches should not be installed in battery compartments because of the risk of corrosion coupled with the potential presence of explosive gasses.”

So...how do you realistically achieve this? On the stringer near the battery box?

My over current protections located near the positive bus bar, some distance from the battery box. Currently (pardon the pun) I am not in compliance.

Jim
Maybe an MRBF fuse like this could be used to feed the bus bar.



https://www.bluesea.com/products/519...k_-_30_to_300A
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Old 12-17-2017, 09:39 AM   #33
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IMO any battery boxes' purpose is to keep them from moving, protect from metal objects shorting them and to contain any spillage.

They should **not** be sealed, up but vented to dissipate gasses released.

Sensitive gadgets should not be mounted directly above the batts themselves, or in the venting path, as the fumes are corrosive over time

but the bank fuse(s) should be - if not within 7" - then as close as possible to the post.

72"??? Where did that come from?

The cutoff switch should also be mounted close, but where you can quickly and easily get to it in an incident or before working on wiring.

Ideally the battery compartment area is designed to accommodate these recommendations. If not then modifications or compromises are in order.
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Old 12-17-2017, 10:02 AM   #34
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Legally??

Looks like title 46 covers commercial boats, title 33 covers gasoline boats. If you have a recreational diesel boat, I have yet to find US legal verbage on wiring near the battery. Must be there somewhere.
There are definately some excellent recomendations, though.
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Old 12-17-2017, 10:17 AM   #35
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Between CMS / Maine Sail http://www.trawlerforum.com/forums/s...d.php?p=617683

and ABYC specifications

that is "the law"

As enforced by surveyors and insurance companies.
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Old 12-17-2017, 10:22 AM   #36
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they cant "enforce" anything cause its not "law".

Surveyors can note and suggest, insurers can insist but can also be convinced otherwise.

Some ABYC standards are mentioned in the CFRS like UL standards, but genetally dont apply to recreational vessels except in the manufactuiring stage.
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Old 12-17-2017, 10:37 AM   #37
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Yes exactly my point.

Great guidelines to follow even if you're self-insured and never going to resell your boat.
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Old 12-17-2017, 10:48 AM   #38
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I am quoting ABYC standards. Over current protection must be with in 72” of the battery terminal if sheathed wire is used, 7” if unsheathed wire is used, over current protection is not needed on a starting circuit but if you tapp off that circuit you are allowed up to 40” to place overcurrent protection.

ABYC also states a maximum of 4 connections to a battery terminal. Many people quote 3, I do not know we’re that comes from but fewer is better give the corrosive neighborhood of a battery terminal.

ABYC is not law, however it’s always my goal to leave any part of a boat that I touch at or above ABYC standard. Some old boats just can’t be brought up to the standard.

You can be with in the letter of the standard but cheat the spirit, this does not make you safe. You can follow the spirit of the standard but be outside the letter of the standard, this does not make you unsafe.
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Old 12-17-2017, 11:58 AM   #39
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Aha, sheathed as in wiring conduit correct? That can increase wire gauge required. . .

Yes, I also think striving for best practices wrt electrics is only sensible.

And CMS has pointed out several areas where the ABYC specs are deficient, like termination pull-test standards.
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Old 12-17-2017, 12:02 PM   #40
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Years ago in my waterfront neighborhood, there was dense, black smoke. I thought it might be a boat fire. Just a few houses down, it was a boat on a trailer. The owner was attempting to put it out with a garden hose. Less than a 20 footer, it was also parked under the eaves, and now he had a house fire on his hands also. No real progress was made until a quint showed up and had it out in about 30 seconds.
It sat around and just looking inside, it seemed likely to me that a long length of wire was responsible, fore to aft. Just a guess though.
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