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Old 08-05-2015, 00:01   #16
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Re: Charging Dilemma .

Quote:
Originally Posted by sailinglegend View Post
Beware this calculator doesn't use there and back distance just the single length from load to battery. Many of these calculators are like this, but they don't tell you exactly what "distance" they require. This chart will give you a cable size that is twice as large as you need - maybe not a bad thing - but a huge extra cost, and profit for the manufacturers as most of these sites sell or make the cables.

Most chart-based calculators use there and back as the distance for their calculations.

Try this one:

Circuit Wizard - Blue Sea Systems
Thank you millions for pointing that out!
Electrics has always been my weak point and I regret i didn't take any courses when I had a chance. Correct wire sizing must be one of the most important factors in boat DC electric circuitry I guess. Get it too thin and bad...
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Old 08-05-2015, 17:31   #17
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Re: Charging Dilemma .

Very sorry about the late reply , the joys of cruising and the internet.
riccorrea2002. I have just returned to Brazil and my boat .I share your grief
DeepFrz , thank you for your solid advice . To answer your question l have the Betta Battery Model No : 6 -CNFJ-100 . Our internet is very sketchy at the moment but their spec sheet is very detailed .
Regarding my cable sizing , are you happy with the 50mm ?
The 16mm tails are very short but l hear you in saying that l should run 50mm right onto the alt . I was advised to go with the 16mm tails from the bulkhead clamp to the engine because of the rigidity of the 50mm cable and the movement of the engine .
I would appreciate your thoughts on my Lead Crystal batteries
Many thanks for your interest .
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Old 08-05-2015, 17:41   #18
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Re: Charging Dilemma .

Allan-
When plumbers have to deal with vibration work-hardening small copper tubing (i.e., the water line that runs into the icemaker and chilled water supply on a refrigerator) they typically put one or more loops, generously sized loops, in the tubing. This tends to mitigate some of the vibration, so instead of having it flex the cable back-and-forth all the time, it spreads out the area of adsorbtion and lets it flex the cable over less of an angle, distributed through the coils.
I'm not sure that having that extra mass unsupported in space wouldn't be an issue, probably some type of rubber mounting would be useful. Just throwing the idea out for consideration.
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Old 08-05-2015, 20:27   #19
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Re: Charging Dilemma .

Quote:
Betta Battery Model No : 6 -CNFJ-100
6-CNFJ-100 12 100 31.50 330 172 220 220
These batteries are rated at 100 ah for 10 hr rate instead of the industry standard(?) for deep cycle batteries which is 20 hr rate so its a little difficult to compare. However at the 20 hr. rate they would be rated at approx. 108 ah. if I have extrapolated correctly. It seems that LA batteries have about an 8% increase in ah rating from the 10 hr to the 20 hr rate. So a little lower than you had specified but not terrible. Other than that I really can't say much (anything). I had noticed that some of their other batteries were rated for a 3 hr. rate which seemed strange to me.

Regarding the flexing of the alternator cabling if you are using marine cabling and there are no sharp bends you shouldn't have a problem. How much does your engine bounce around? The calculator recommended the 1 AWG (44 mm2) wire but also suggested that 4 AWG (21 mm2) could be used if you aren't concerned with the 3% voltage drop. I'm just concerned that the 16 mm2 is causing to much of a voltage drop so ensure that your sense wire is coming directly from the batteries.
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Old 09-05-2015, 08:17   #20
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Re: Charging Dilemma .

If the 16mm wire is short (<0.5M) it is ok.
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Old 09-05-2015, 20:02   #21
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Re: Charging Dilemma .

Hellosailor . My current installation has the 16mm tails ( Transmitterdan approx 500mm length ) hung in a gentle U loop from the bulkhead clamp to the alt allowing hopefully a stress free installation for the cable .
This came about after a bad experience when my first method of the 50mm neg cable direct to the alt sheared behind the crimp on the lug almost resulting in a fire onboard . Had it not been for my wife's keen sense of smell , l reckon we would have gone up in smoke . The fault in that instance was either a bad crimp or the lack of movement in the cable from the bulkhead to the engine . That is when l was advised to go to the lighter 16mm and increase the U loop to allow for the movement of the engine which ( DeepFrz ) is a bit wobbly on idle otherwise smooth from high idle upwards to my normal motoring rpm . I am pleased you feel that the cable is sized correctly .
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Old 09-05-2015, 20:20   #22
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Re: Charging Dilemma .

I would like to ask you guys a simple but possibly a stupid question . My background is hydraulics and pneumatics and we avoid at all costs doing installations that have tight bends or 90 degree changes in direction because of the restrictions they create in flow .

Does the same rule apply with DC current ? My installation has the 50mm POS and NEG cables coming up vertically alongside the engine to the bulkhead clamp and then the two 16mm tails falling back into U loops to the alt . In other words in hydraulic terms bad news as the current flows up to the end of the 50mm and then reverses direction down through the loop onto the alt .

Please forgive if my question is ridiculous .
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Old 09-05-2015, 20:58   #23
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Re: Charging Dilemma .

No, the bend shouldn't restrict current flow. At least I have never experienced a problem with that sort of thing. The previous problem with the larger cable was most likely because it wasn't secured ahead of the cable connection. Was the cable connection soldered by any chance? In any case the cable shouldn't be allowed to flex at the connector although it can be difficult to find a good place to secure the cables.

Edit: The cables should be secured to the engine before leaving the engine and in that way the flex will not be at the connector.
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Old 09-05-2015, 21:14   #24
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Re: Charging Dilemma .

Allan-
In the US, that 50mm2 cable would be a little thinner than a 1/0 ("0") AWG cable, and somewhat thicker than a #1AWG cable.
Considering the way that so many people say "crimp your cables, if you solder them they will work harden and fail" I guess we have proof here that crimped cables are not always any better than soldered ones.(G)
Without knowing how it was crimped, it is hard to say if that was just a bad crimp. Many "crimps" are just staked, or crimped in whatever die is at hand. unless they come from a "professional" facility or maker.
What you have no works for you, so...it is apparently doing the job. A "u" shaped bend will relieve more vibration than no bend, and of course electricity does not suffer flow restrictions from friction and turbulent flow, etc. that fluids in a pipe would. I suppose that somewhere, someone, has standards for installation issues like these, but that might take some sleuthing to find. And even more to find out if their standards had ever been laboratory tested and proven.
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Old 10-05-2015, 19:54   #25
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Re: Charging Dilemma .

Thank you for your replies and l feel quite comfortable now that my problem is not in my cabling sizing but lies elsewhere .

From this post l have learnt a lot and will now conduct some tests to establish where this problem of low current output could be .
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Old 11-05-2015, 17:35   #26
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Re: Charging Dilemma .

Just one more question, even if you plug the shore cable you can't go above of 55 Amps?
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