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Old 29-05-2009, 10:35   #1
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Join Date: Dec 2008
Location: SF Bay Area
Boat: Searunner 37 trimaran, Islander 34
Posts: 271
First Electrical System Design

Hey folks,

I'm a newbie to boats, but I'm pretty handy with a soldering iron. I've recently moved aboard a 37' Brown Searunner trimaran, and I'm loving every second, learning to fix wood problems, engine troubles, fiberglass, etc, etc. Now it's time to tackle the electrical system, which are working somewhat decently but there's just not enough battery capacity and the Link10 monitor is apparently dead. I've been working away at the system, but I'm thinking it might just be time to start from the bottom and work my way up, instead of trying to patch and repair what's here.

Seriously, so far most of what I've done is tear out old, unused wiring... and there's a *lot* of it! Runs of 20-year-old wiring from one end of the boat to the other, with the ends lopped off years ago and decaying electrical tape sealing off the cut ends, that sort of thing. I haven't removed anything that's actually working, just the stuff that's obviously not in use. The main electrical "area" is 200% cleaner now - it still looks like a rats nest, but now it looks like the rats at least went to trade school.

I'm thinking it's time to rip (most of) it out and build a firm foundation, then add the working current stuff back in bit by bit.

My goals with this system:

- I will very rarely be attached to shore power. I do not have moorage, and intend to spend most of my time at anchor, cruising around the Gulf Islands. Currently I have a small gas generator, but eventually I would like to add photovoltaic panels, a wind turbine, and possibly a water turbine.

- I'd like to have a decent amount of reserve power, ideally enough to run a small computer (mac mini with a draw of about 35w) for a couple of days.

- I'd like to use modern, reliable components that will allow me to expand the system (ie, add solar) slowly, as I can afford to.

So, what I've come up with so far is a pair (or more) of large AGM batteries for the house bank, a separate starter battery for the engine, an intelligent charge controller and a monitoring system.

My questions:

- What brands of AGM batteries have you had great experiences with? Any bad experiences?

- I've been looking at the Xantrex 'Freedom Marine' charge controllers/inverters. Any opinions on these? Any other recommendations?

Any other tips? I've been reading sites where I can find them, but it seems like most designs center around being attached to shore power most of the time. Hell, I just pulled out all the wiring for the shore telephone and television connections - I don't own a TV and I've been 100% cellular for years.

I'm wide open to recommendations of sources of reading, etc, also - though ten words of advice from someone with hard-won experience trumps a thousand words from generic technical manuals any day of the week.
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Old 29-05-2009, 12:48   #2
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Quick thoughts...sorry I don't have time for detailed response now.

1. It's MUCH easier to rewire a boat once you pull out all the old stuff. Trying to work around the mess that's there is pure hell.

2. AGMs have advantages and disadvantages. One of the principal advantages is that they can be charged more rapidly that flooded cells. HOWEVER, with an EU2000i you won't be able to take advantage of that capability...not nearly enough power.

3. No way are you going to get a real 100A charge into your batteries with the Honda generator. 75A is about all you can expect, and that's pushing it a bit.

4. Iota chargers are inexpensive and very sophisticated. Pulse-width modulation technology used is suitable for both AGMs and flooded batteries. Most bang for the buck you can find in a VERY WELL CONSTRUCTED, AND VERY WELL DESIGNED charger. They come in various sizes, 10A to 90A. Don't try the 90A model with the Honda....maybe you can get the 75A model to work OK, as some others have. The Iotas put out more AVERAGE current than most chargers, and they consequently draw more INPUT current.

5. If you do go with AGMs, remember that they must be FULLY CHARGED at least once a month. At anchor and with Honda gen charging, you'll likely be working between about 40-50% depletion and 20% depletion, since it takes a LONG TIME to fully recharge the batteries. A big solar panel would help, provided that it's got a good controller/regulator.

6. I'd avoid the Xantrex chargers. Quality varies and after-sale support sucks, to say the least.

7. Depending on your daily draw (you need to calculate this out), you'll likely need between 450AH and 675AH total house capacity (equal to, say, four to six 6V golf-cart sized batteries).

Hope this helps a bit. Sorry I don't have more time at the moment.

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Old 29-05-2009, 13:06   #3
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What type and how many batteries do you have now? How old. If you replace your batteries, do it as a set so the are all the same type and age. Get a book and make a plan. I had trouble with my system even after I had it checked out. I then pulled all the batteries out and put them on the dock. I charge each one with a charger that checks for internal faults. When they were all charged I left them still for 48 hours. Then voltage tested and all were the same, then load tested them with a big toaster looking thing. all were fine but one. The voltage said it was full but it whet entirely flat on a load. Replaced that one and the system was much better. Hope all goes well. There is some great info here and on sailnetdotcom Read read read. Calder or Casey You dont want to have to do this twice
That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.
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