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Battery size needed


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You could probably get away with one of the sealed 12v batteries that they use to power alarm systems but for not much more I would get a small size car battery that could run a few other things if it had too. Be even better if it could start your motor.

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There is another way to be looking a this.

Your House Bank should be a few Hundred Ahrs, so even when flat (50%), running the Navman would not be much of an issue to it. In other words, 12Ahrs of further discharge on 200Ahrs of House bank is not going to be of major concern, as I am also assuming this is not a regular issue. If it is regularly flat, you need to get a bigger House bank.

Or you could get a Solar panel. It would be cheaper, will charge your House at the same time as supplying some sunbugs to the Navman and then hopefully, there is enough charge for the House bank to get through the night.

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I still suggest a slightly larger Main battery. But Vic has not given us the full story here.
Why is his main battery going flat?

How flat is flat?
If by meaning Flat is absolutely nothing left, then he needs a bigger main battery. Or he is going to need to replace it often.
If he means flat as in 50% down, then lets say it is a really small 100Ahr Batt. 600mA/hr (= 12Ahr over a 12hr period) is a very small draw and that is not going to be detrimental in anyway to the Batt.
Replacing the 100Ahr with a slightly larger Batt, say 150Ahr, could be a win win in every sense. The Batt is not discharged as far, thus will last longer, or whatever is discharging the Batt can be run for longer and the extra 12Ahr is catered for. No extra wiring, no extra gear to charge a separate Batt and so on.

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I'm with Wheels on this. Easiest thing to do, no additional bits or alterations to wiring, Why complicate things, and by the time you start taking your time into account and buying all the bits for other options, probably no more expensive.

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Something else to consider is wiring size and quality. Not a lot of energy is lost through bad wire but some cabling particularly Chinese stuff is quite high in resistance. I have even come across 'fake' stuff, steel thats copper coated! Short runs probably not a issue but small gauge will rob you. A larger voltage drop.

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To get to that stage shows very poor vessel management. A 13hp will run a 50/60 amp alt, no problem.

A decent jump start pack will provide the power you need as a last resort.

Cabling:

Be aware everyone, you are LEGALLY REQUIRED to use cable that meets AS/NZS5000.1 on your boats. Just because only surveyed boats actually have this checked, does not exempt you. This could potentially have insurance ramifications, if you update something, or add something, and it causes an issue later. There is a lot of substandard cabling available here in NZ, including from "reputable" suppliers. If your supplier or marine electrician says your not in survey so this is OK, proceed with caution!

Again, the standard is 5000.1

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This is a new one on me! I have done installation work and had no idea recreational vessels not used for hire or reward are legally required to have certified wiring for dc supply!!!? Can you please link to the regs for this? Act?

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Yep, it’s in the 2008 regs, which are the current legal regs. The newer one is not yet law. I’ll find the relevant section and post it tomorrow when I’m in the office. There is no exemption for recreational vessels.

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Everything I can find is only related to wiring that is capable of being fed by mains (shore) power. The only low voltage DC regs relate to commercial vessels. This very interesting! I look forward to your info.

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There is no difference between Commercial and Private. Same applies to AC and to Gas.

More confusion..are you saying this "illegal" wiring is AC MAINS or DC? Or both? Another search on line and I can find nothing relating to DC wiring in private vessels? Time to hit the phone..

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Hmm..MSA "not sure, ring a surveyor" (Thomas). Rang Dansford Marine and spoke with David Potter who said there is also standard NZS3004.2 and IEC6009.350 but it is not illegal to wire your own boat and thought the word "illegal" is a bit out of place as any wiring should be of sufficient robustness for its intended use, on or off shore. Essentially Island Time is right in as much as there are standards for wiring but use commonsense when passing high current through conductors that are of sufficient size. At leased thats what I understood he said.

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You probably cant find it online for free. You have to BUY the standard (Which is stupid!!)

The Standard is AS/NZS 3004.2, section 6 is the appropriate area;

 

"6.1 SELECTION OF CABLES FOR MARINE ENVIRONMENT

Cables shall conform to AS 60092.350 or AS/NZS 5000.1.
The conductors used in cables shall be annealed copper with cross-sectional area, stranding
and conductivity conforming to Class 2 or Class 5 of IEC 60228 or AS/NZS 1125.
The use of solid conductors (single wire) and the use of aluminium conductors is not
permitted.
6.2 CABLE SELECTION AND INSTALLATION
Cables shall be selected and installed in accordance with—
(a) AS/NZS 3008.1.1 and AS/NZS 3008.1.2; or
(B) IEC 60092-352; or
© Table 1 of IEC 60092-352 plus Clause 6.4.
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Let me update you on this.

I have a job next week, on a boat about to go into survey. The discussion about these cables was had with the electrical surveyor. It is not legal for ANYONE to use substandard cable on ANY vessel. Only the surveyed ones are checked though. These are his words.

My job is basically to remove all the wiring, which is in good order and well installed, but it is stamped with the NZ well known marine industry suppliers name, and the words " does not comply with AS/NZS 5000.1" . Why any reputable company would sell such cable is beyond me.

I'm going to do the work, he will inspect and sign off. This is all DC stuff, not AC. (I'm not a registered electrician, can't do AC)

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Ha! Have the same problem, electronica trades cert with electrical fitters endorsement which I needed (Aussie) to work on mains single phase powered equipment but can not do certification work on the mains side (geyond the plug!) unless the work is signed off by a qualified electrician. Makes sense, to get the "endorsement" required sitting in front of a video then answering a few questions! Good luck on your wiring. This has been an interesting exercise for me, thanks IT, now retired but do mates jobs from time to time (repairing a TV tomorrow) and have seen atrocious wiring in some boats!

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Err, unless the regs have changed yet again...has it. I can't keep up. Mind you, I have let my Registration lapse and don't attend the courses anymore. I got annoyed I had to have a 2 yearly First aid cert when I was working on my own anyway.

Anyway,
it was once a case that you could not do electrical wiring full stop, if it was for someone other than yourself. ie your own home. You could not do any work within the switch board full stop and any of the other work had to be inspected and signed off in compliance before it could be used.
Those like me with limited reg can do work on any appliance up to the wall connection, disconnect and reconnect, but no new appliance (like an Oven) can be connected to the wall connection by other than a full sparky.
So no, IT can not install AC. Which is ridiculous in reality. DC is no more " safe" than AC as far as cable selection, installation requirements under the act, termination and whatever else. In the end, no one other than a sparky can connect AC to the switchboard. So why can't anyone install AC wiring as long as it is inspected and conforms to the regs and then connected and tested by a sparky. Really the only main difference between AC and DC is AC has an Earth wire and proper earthing is required.
 

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