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Old 08-04-2019, 16:08   #31
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Re: Where can I find new terminals for this cable?

So, I'm leaning towards installing two battery studs on a piece of wood, epoxying it to the hull and bolting the existing giant cable to the studs, then a 1.5' piece of 4/0 cable from the studs to the inverter/charger. From what I understand, this should not introduce any undue resistance and since the run of 4/0 cable will be so short, I am still getting whatever advantage there might be from the remainder of the giant cable (to my understanding, that advantage is low voltage drop and increased life of the cable because I am only running a fraction of the amperage through the cable compared to its design specification, which is 724amps).

But, I want to try and learn why many people seem to be saying there is an inherent problem using oversized cables, but others are not saying that. Yes, it is apparently not to ABYC specs, it exceeds them. Why is this bad?

The original cables were installed 19 years ago by a guy who worked at a boat yard where I had the original inverter/charger installed. I did not supervise this work 19 years ago, although I paid for it and the inverter/charger has worked great for 19 years, never a problem (until last week when I soaked it accidentally and fried it).

I think I know a lot more now than I knew then, but I still don't understand what the down-side is to using an oversized cable, in this specific scenario.

If I believed there was a down-side (other than the difficulty in crimping new terminals) then I might decide to go to the hell of swapping them out for 4/0 cables (which everyone seems to agree are the right sized cables to use for this application, though one guy I talked to said 2/0 was sufficient).

I always thought that the bigger the cable, the less voltage drop and less wasted current. So, what is the down side to using these oversized cables?

Thanks to everyone who has commented so far! Really appreciate the input.
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Old 10-04-2019, 16:34   #32
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Re: Where can I find new terminals for this cable?

In case anyone is interested, here's where I ended up. Oversized DLO cables routed to a pair of battery terminal studs which I screwed into a block of wood that's epoxied to the hull. Then a pair of 18" 4/0 "patch" cables to the inverter/charger. Everything is purring away.

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Old 10-04-2019, 19:00   #33
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Re: Where can I find new terminals for this cable?

Nice job. Go to Lowe’s and get an electrical box with a cover for protection
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Old 10-04-2019, 19:56   #34
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Re: Where can I find new terminals for this cable?

Quote:
Originally Posted by meridian28 View Post
Nice job. Go to Lowe’s and get an electrical box with a cover for protection
Piece of vinyl hose split down one side and screwed to the top of your block works well to prevent accidental shock. You’ll prob need some 1.5” to cover that. You can notch the cable sides to get a custom tight fit.
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Old 10-04-2019, 21:01   #35
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Re: Where can I find new terminals for this cable?

that 4/0 looks like a twig next to that mcm. crazy
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Old 11-04-2019, 05:06   #36
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Re: Where can I find new terminals for this cable?

Quote:
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... These handy tools are readily available for $20. Will reliably crimp #8 - 4/0.
https://www.ebay.com/itm/Cable-Hammer-Crimper-Tool-Battery-Welding-Wire-Terminal-Lug-Connector-8-4-0-AWG-/132074169267 ...
The O.P.'s 500MCM+ cable will have a diameter of about 3/4". I've never seen a hammer crimper designed for cables that large.
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Old 11-04-2019, 06:24   #37
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Re: Where can I find new terminals for this cable?

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But, I want to try and learn why many people seem to be saying there is an inherent problem using oversized cables...
No one has said that. What they have said is that appropriately sized cables would be much easier to work with, and would cost less than buying a crimper just for that grossly oversized cable. Which, it appears, is the conclusion that you have come to.
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Old 11-04-2019, 08:23   #38
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Re: Where can I find new terminals for this cable?

I always solder mine, crimped or not. Once the copper corrodes inside the crimp or adjacent, and battery cables ends always do even if it's just the formation of cuprous oxide, it creates resistance. Crimp, solder and you are good to go.
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Old 11-04-2019, 12:26   #39
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Re: Where can I find new terminals for this cable?

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Once the copper corrodes inside the crimp...
If the crimp is done properly, this is impossible. Solder is a fix for a bad crimp. With a proper crimp, soldering buys you absolutely nothing.
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Old 12-04-2019, 21:19   #40
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Re: Where can I find new terminals for this cable?

Quote:
Originally Posted by rbk View Post
Piece of vinyl hose split down one side and screwed to the top of your block works well to prevent accidental shock. You’ll prob need some 1.5” to cover that. You can notch the cable sides to get a custom tight fit.
I did cover the terminals after this photo was taken (with these: https://www.amazon.com/Fastronix-Mil...df_B01068FSJI/). I had to "modify" them a bit and use cable ties to secure them.
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Old 15-04-2019, 07:29   #41
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Re: Where can I find new terminals for this cable?

I don't know what kind of loads you've been running but is the cable fried and brittle inside from overheating? Otherwise I would think you could unsupport it, make your curves a little bigger and remount to remove the excess.
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Old 15-04-2019, 07:47   #42
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Re: Where can I find new terminals for this cable?

This thread was really interesting to read...

What is the actual Amp that can run on the cable before a fuse is blown? What length and what is an acceptable voltage drop on the cable for your implementation?

An oversized cable will create less voltage drop but is more expensive and harder to work with. Without knowing the requirement of the cable it's impossible to know if it's oversized or not.


Still think the best and most possible cheapest recommendation you got was to order a new cable with the correct size, lugs, and length based on the fuse, load, and acceptable voltage drop.
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Old 15-04-2019, 08:42   #43
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Re: Where can I find new terminals for this cable?

Do you NEED the cable to be this big, especially if you are shortening the length? I would reconsider removing it and buying the appropriate sized cable. It will be smaller, so easier to install, and likely lighter to boot. Lugs are cheaper and crimpers more readily available. (West Marine stores usually carry x/0 cables and lugs, and usually also have the tools to cut/crimp them for customers to use -in store- for free.)

Once you cut that cable, there is NO going back if you ever want/need to.
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Old 15-04-2019, 09:32   #44
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Re: Where can I find new terminals for this cable?

You should be able to rent a crimper and a cable cutter from electrical company that services the commercial electrical business. Here in southern Ontario “all-trade” is one company we use
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Old 15-04-2019, 10:19   #45
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Re: high ampacity DC cable connections

I agree that the best electrical connection is a proper crimp followed by soldering to prevent corrosion. The terminal connector has to be suitable for the cable conductor stranding. Fine stranded cable requires special connectors and crimp tooling.


The use of terminal posts joining short patch cables is clean. There needs to be a rubber boot covering each pole to prevent inadvertent short circuit.


Finally but not the least importance, each leg of the DC bus between battery bank and inverter/charger needs to be fused that is rated to clear a high amperage DC arcing fault. Rectifier failure mode includes failing in a short circuit, which if occurs in the inverter/charger leads immediately to generating an electrical fire.



I suspect many marine electrical fires involving inverter/chargers occur when the DC bus was not properly fused to isolate the battery bank from the inverter/charger in the event of bridge failure.
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