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Old 22-05-2010, 15:40   #1
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A 12vdc Boat - KISS ?

About a week ago I started a thread seeking advice regarding how to make a boat compatible with different shorepower voltages worldwide. My current project is a 42' mono that the builder is half way through. The best advice I was given was to buy a copy of Nigel Calder's Mechanical and Electrical handbook. Having taken the advice and now read the electrical sections of the book, I am convinced that there are definate advantages in building a 12 volt boat without a generator or even an inverter, but simply a charger that can hook up to 110v - 240v shore power. I prefer to build the boat with good shade and ventilation rather than install air conditioning. It has huge tankage (1100 litres) and deck infills rather than a watermaker. I can buy a 12 volt microwave and keep my laptop charged with an in-car charger. Everyone, including the builder presumes I will want AC power. Why do I need it? Am I missing something ?

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Old 22-05-2010, 16:26   #2
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The only advantage I have found with AC power onboard is for using small electric heaters while at dock, and running the hot water heater at dock also. A guy at our marina who has cruised for 5 years before returning said that he would occasionally run his honda generator to heat water to take a hot shower, which was very useful in his eyes when out on the anchor and it happens to be cold/wet.

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Old 22-05-2010, 16:39   #3
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I have read that some of the 12 volt chargers for laptops don't charge them all that well. They may have improved more recently though.

A lot of the time mains voltage appliances are much cheaper than 12 volt versions. But certainly you can do without it.
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Old 22-05-2010, 16:53   #4
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While cordless drills are great, some drilling jobs need a corded drill, or dye grinder, or Dremil tool.

Keep a small inverter onboard and you should be all set.
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Old 22-05-2010, 17:09   #5
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Think about a heavy duty alternator with external controller for those times when away from the dock. Maybe some solar too.
If you will have refrigeration, look for one with a native 12 V compressor.

12V LED lighting and forget the TV and stereo.
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Old 22-05-2010, 17:32   #6
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G'Day Greg,

I think that you are on a good track here, but suggest that a small (<1kw) inverter will be useful and not very dear. I'd suggest a modified sine wave model without an inbuilt charger... more reliable and much cheaper than the top of the line ones on offer now.

We've found that buying 12 volt gear to replace stuff that is normally mains powered is not cost effective at all, and much of it is poor quality. Things like small kitchen appliances, small battery chargers for AA and AAA cells, power tools and their battery chargers (if battery powered), computer stuff and so on all work off of small inverters without problems.

We don't have an elaborate mains power distribution system... just a couple of outlets wired to the inverter. I can't speak to the idle current loads associated with the newer inverters, but our 22 year old 600 watt Heart Interface model only draws about 50 mA at idle, so we leave it on 24/7.

One specific item: the DC to DC converters used to power laptops from 12 volt systems are often VERY noisy (that is RF noise).This means that if you want to use your computer in association with any HF gear (weatherfax reception or on-board HF e-mail) you have problems with receiving weak signals. Running off the laptop's internal batteries takes care of this, but this means keeping a good set of computer batteries charged... and so on.

Anyhow, I think that what you are considering is a good practical long term approach. We're happy to answer any specific queries, as always.

Cheers,

Jim and Ann s/v Insatiable II lying Bayview, NSW, Oz
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Old 22-05-2010, 17:42   #7
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The only advantage I have found with AC power onboard is for using small electric heaters while at dock, and running the hot water heater at dock also.
This is it in a nutshell. If you plan on spending a bunch of time...at any time during your ownership...living aboard at a dock, setting up a very basic AC system is a good idea. A small integrated inverter will help you run the occasional drill or vacuum offshore too. IMHO, Chris
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Old 22-05-2010, 18:38   #8
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laptops actually run on DC and the AC adapters are small/cheap modified sinewave inverters...laptops (and all electronics) are alot happier with pure sinewave inverters ...or better yet straight DC.
In rewiring my boat I am trying to get as much 12v as possible, as I live aboard I keep some AC wiring.
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Old 22-05-2010, 18:59   #9
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I think you are on the right track for future boats that will be all DC… even large ones with all the conveniences.

The Victron “The Book” is a very good primer for power management and as y9ou can see from watermakers and even air cons….DC is becoming the goal

http://www.victronenergy.com/upload/...yUnlimited.pdf
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Old 22-05-2010, 18:59   #10
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A most fortunate thread. Our new (for us) boat had a Xantrex Freedom 20 Charger/Inverter that seems to have taken a crap. They look to be about $1,200 for replacement. But, just today, I went to Pep Boys and found I can buy a 3,000-watt modified sine wave inverter for $350 or a 2,000-watt model for $250 and their best three stage charger for $100.

Our boat has wind generation, and solar, and alternator and NOTHING that runs on 120VAC.

When we put in a heater it will be Espar or other diesel system, running on 12 VDC.

Hell, we don't even have a TV or AC in our house.

So, why indeed?
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Old 22-05-2010, 19:23   #11
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Important on the inverter to either buy a pass tru unit ot you will need a $200 transfer sw My boat is all 12 volt except for the hot water heater An inverter is very useful Are the 12v microwaves any good how much power do the consume?
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Old 22-05-2010, 19:26   #12
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are you running so much stuff at once that you need a 3,000watt inverter, because if you don't it is an incredible waste of power. I have two inverters a 200watt and a 700watt. Inverters are most efficient around 60-80%, I use a 200watt inverter for a 3.6cubic foot AC refrigerator/freezer (it only uses 180watts when running).
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Old 22-05-2010, 22:56   #13
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Everyone, including the builder presumes I will want AC power. Why do I need it? Am I missing something ?
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Greg
(I haven't read any other replies)

Greg, you are missing nothing! You are just copping all the expensive crap from people trying to cost you money.

We now never need shore power.

If we do I just run an extension cord into the boat from the shore power socket. The sockets and plugs I just buy locally.
The last time I needed to do this was when in an Asian marina, before my solar pannels were installed, and I wanted to run a big domestic fan.

Folks that bought air conditioners could have done the same thing. Electricity into the boat does not have to come through cute integrated little electrical sockets: an extension cord and power board if necessary is fine.

The last tmie I used the battery charger was pre-solar panels.

We have never used the shore power water heater for a few reasons: 1) we'd be at a marina so they have showers
2) in the tropics so cold water is fine
3) if necessary I'm sure it could be connected as above
4) if necessary I'm sure it could be done via a big inverter.
5) Because it was winter here when we arrived we somethimes ran the engine for 15 mins to warm the shower water

By the way, our only inverter is a 150 watt computer type one. That does everything including drill batteries, camera batteries etc

KISS is good! Also non-fear is good too. Electricity, water and LPG gas are survival things in 100% of the world. They all have cheap simple solutions to what you may think are problems.

e.g. we 'change' LPG gas systems on arriving Turkey to the European system. Cost: $7 for a new regulator. I cut off the old one, bunged on the new. No worry, no panic, no certified gas fitter! KISS.




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Old 22-05-2010, 23:11   #14
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I have read that some of the 12 volt chargers for laptops don't charge them all that well. They may have improved more recently though.
They must have improved a fair bit.


Greg, this 300watt inverter from Jaycar for $80
300W (1000W Surge) 12VDC to 230VAC Electrically Isolated Inverter - Jaycar Electronics

This is the wattage we have ($50)
150W (450W Surge) 12VDC to 230VAC Electrically Isolated Inverter - Jaycar Electronics

And this is the one we have at about $100:
Targus*|*APV14AU*&ndash;*150 Watt Auto/Air Power Inverter - Slimline Style

So if I was buying a new one I would get the Jaycar 300 watt, not that we have apopeared to need the extra 150 watts.

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Old 23-05-2010, 00:33   #15
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Another view.
I have a 5 kW generator coupled to two DC alternators. I have no gas. I cook with electricity (240V), during that time, I normally put back 70 Amps into my battery, run my freezer (240V) and do anything else that require electrical power. Having that installation I do like Mark run one lead to the lot when shore power is available. I do not believe in the future of 12 V dc installation they are far to heavier.
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