Philip, Now your situation is becoming more in focus.
I agree with Lew, the first thing to do is to make a written/drawn description of your DC system. Complexity provides flexibility. Don't be afraid of it. There are some folks that insist on the KISS approach. Simplicity is easier to comprehend, usually rugged and easy to maintain. Student pilots fly simple, rugged airplanes, but the real workhorse aircraft are called complex aircraft. Trainers fly around the local area, the complex aircraft go everywhere. They are complex to be able to deal with all the conditions they will need to handle. So don't be in a hurry to rip out everything and start over. All those battery banks and switches give you the flexibility to deal with various conditions. I would make a schematic drawing of the DC system, especially the alternators, the heavy lines and the big red switches to get an accurate picture of the current situation. As you might be aware most of us have an engine starting battery and a house battery. Having an windlass battery in the bow is to avoid running heavy copper from the house battery to the bow. You put a battery up there for the windlass and feed it with a relatively small charging line. I tried this once but it just "didn't work out", the battery was usually dead when I needed it. Today one of Ann-Marie's combiners would have undoubtedly prevented that problem, but even then, you still have one more battery to maintain and replace periodically. That experience was original reason I ran the two 00 twisted pair lines from the house batteries to the bow. One pair up the hull/deck join on the portside, the other up the hull/deck join on the starboard side. They meet at the solenoids that feed the windlass motor. The windlass can draw up to 300 amps and I didn't want the voltage to sag too much. It took days to do, of course. Once I had the two twisted pairs in place it was a no-brainer to power all the other 12 VDC loads off the twisted pairs. Why run load pairs from the house battery when there was already all the power in the world available right there in the twisted pairs feeding the windlass. I came up with the soldered-on offstickers and fuse/terminal/block as the easiest, most reliable, way of doing the job. I extended the idea to the stern and it has all worked wonderfully well ever since. So this leaves a starting battery for each motor and the house battery. I have long though it was a good idea to have a separate genset start battery. There have been some scary moments in my past when I had closed the house/start battery crossover switch to connect the two together to start a reluctant main engine and forgot to open it after shutting down later only to find much later that I had discharged not only the house battery but the engine starting battery too. I was extremely grateful that there was just enough juice left to start the genset and get me going again. I bless the day I installed Ann-Marie's combiner. Since then I have never had to double up the engine/house batteries to start the main (the combiner and a valve job on the main) and the genset always spins merrily when I go to start it so I have never since felt that punch in the gut when you realize all your batteries are dead. Bottom Line: If your boat were my boat, and I decided to do a rebuild of the DC electrical system, I would replicate my buss system, but leave the genset start battery in. I would connect both the engine start battery to the house with a combiner, and the genset start battery to the house with a combiner. In case you don't know, a combiner is a smart relay that closes (connects the two batteries together) when one of them has a high enough voltage to indicate that it is being charged, so both batteries get charged. This way, if any battery is being charged, all batteries are being charged. Another Good Thing would be to be sure your genset start battery alternator is working. Mine is not, it is an expensive and undersized. Some day I would like to replace it with a standard $50 automotive unit but I would have to fabricate another bracket, but for now it is just and idler pulley. My inverter handles the charging duties after the genset is started. Yet another Good Thing would be two alternators on the main engine, one $50 auto type to maintain the starting batteries, another 200A powerhouse with external 3-stage regulator to charge the house batteries. Finally, the design of your vessel is in your hands. USCG construction rules apply only to the original manufacturer and ABYC to insured boats. It is one of the major attractions of the boating life if you love to play with machines. You can be an actual engineer, (actually, you MUST be an actual engineer) in this lifestyle. It is great fun to dream up excellent ways of doing things on your boat and figuring out how to eliminate problems so your can devote more time to cruising and partying, and deeply satisfying to find a way of doing something that really works better than the "standard" way of doing things. I did buy the ABYC standards book many years ago when I started to build Bandersnatch, but found the updates increased in price every year until the cost/benefit ratio got too steep (it is created for manufacturers), and I actually often did better than the book. As they say: "Do it right, or do it over". Norm S/V Bandersnatch Lying Julington Creek 30 07.695N 081 38.484W > [Original Message] > From: Philip McConnell <[EMAIL PROTECTED]> > To: <[email protected]> > Date: 7/23/2008 8:26:27 AM > Subject: Re: [Liveaboard] 12 VDC buss > > Norm, > > Part of the problem is that I'm just not as familiar with the terms and > concepts some of you more experienced guys use. I'm sure you noticed Lew > tried to flesh out the concept more for me (which I appreciate) which > helped but I still don't think I've completely "got it". Where many here > are going "Ah ha! of course!" I tend to be going "Huh?" I'm sorry I > didn't get up where you are before we headed farther south. Seeing a > thing works much better for me if I'm unclear on a concept. > > I do need to figure this all out too. My boat has the basic Tayana > factory wiring modified to support four separate battery (genset start, > propulsion start, windlass, house) banks using two 1-2-all-off switches > and two plain on-off switches. All this Rube Goldberg arrangement does > is ensure that at least one set of batteries is dead at the most > inconvenient time. > > Philip McConnell > USSV Gryphon > In pieces, Ft. Pierce, FL > _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [EMAIL PROTECTED] To unsubscribe send an email to [EMAIL PROTECTED] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
