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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 11-03-2007
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12V electric system ideas

Hi, I am looking for information on whether or not the electical system on the boat I just bought is a good system or if it should be changed. It has 4 battery banks, 4 battery switches(Three A-Both-B-Off, and one On/Off), a charger (don't have make/model), two alternators(Balmar), two 55W solar panels, and a 1500w inverter. I only have experience with a two bank system with one switch, and knowledge gained here from reading threads). It seems that 4 banks is overkill redundancy and unnecessarily complicated to me, but really don't have the experience to say(I'm a keep it simple advocate). We will be sailing in the Pacific NW for hopefully 2-4 months at a time with long stretches between shore power hook ups. Unfortunately, the boat is in Hawaii right now and I am in Seattle so I can't answer too many questions but would like opinions about what would be the optimum system. I am willing to completely re-do it so that it is bulletproof if necessary, but obviously it would be easier and cheaper to leave it as is or modify somewhat(obviously it has worked since 1988, South Seas, etc). I intend to replace all 7 batteries (there are 6 6V and one 4D now, all old), haven't decided whether to go AGM or wet cell yet. The wiring that I have seen seems to be professionally done (except for some minor stuff the PO did) but I haven't had time to track it all and figure out what goes where and how it all works(lot's of cables, shunts, etc, somewhat intimidating). From reading other threads about wiring systems it seems a three bank system is favored with one a dedicated start bank and the modern chargers have the ability to charge three banks, how would 4 banks be charged? Thanks in advance for your input, sorry I can't supply much more info. than this, I am trying to plan what I'll need in advance of the boat arriving in December when I will go to work on it. John
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Old 11-03-2007
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Hi John,

Sounds like you (and me for that matter) could benefit from a good but basic book on recommended 12V marine systems.

Could someone recommend a good book?

I understand this one is good:

Boatowner's Mechanical and Electrical Manual, 2nd edition
by Nigel Calder, Stephen Pollard
International Marine Publishing
Hardcover
THE best book on the variety of maintenance issues on boats. Covers boat maintenance, mechanical and electrical systems, sails, rigging and more. SAIL magazine says "This book should come as standard equipment with every boat."

http://www.amazon.com/exec/obidos/AS...uewatersaili0f


Any opinions?

Fred
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Old 11-03-2007
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How large a boat is this ? That is a lot of battery power. The solar panels seem small for 4 banks of batteries. With two Balmar alternators, sounds like he needed or choose to use the engine to charge the batteries. Do you know your total AH ?
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Old 11-03-2007
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I suspect you could live with half that storage capacity, but I wouldn't change anything until you drew and understood a schematic of your current system. The power requirements in the tropics can be extreme. I doubt you will need a watermaker and referigeration will require much less power.

Calder's book is a good start.
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Old 11-03-2007
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The boat is a 40' pilothouse. I don't know the total AH, just bought the boat and have only spent one afternoon and night on it. We will be running refrigeration and hopefully the SSB for email(not sure how you do that yet, but we're hopeful), and the usual lights, water pumps, etc. We have gotten by up until now with one 8D deep cycle as a house battery on our last boat with no problem, although no refer. John
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Old 11-03-2007
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As far as refrigeration, on my boat I have an Engel 45. It draws .07 amps an hour. Really depends on what you have and what your needs are.
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Old 11-03-2007
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John,

As others have said, it's really impossible to comment intelligently on your electrical system until we know exactly what you've got and how it's connected. From your brief description, here are a few hunches:

1. All new batteries is a good idea.
2. Flooded batteries are most cost effective; AGMs are great but 2-3 times the cost.
3. Six 6-volt batteries, assuming they're golf-cart size (like the Trojan T-105s) are about right for house batteries on a 40 footer. This is enough to run refrigeration and most of the usual stuff.
4. The 4D may be a starting battery.

With four switches, it would seem that someone has divided the golf-cart batteries into three banks of two each (i.e., 12V each in three banks) plus the 4D, and has put a switch on each bank. This is just a wild guess; it may be otherwise. But until you've traced and diagrammed the entire system, you won't know whether it's workable for you or not.

In general, it's best to have one large house battery bank. This can be done by wiring them all together or, in some cases, using battery switches to combine them into one large bank if desired. I have six golf-cart batteries connected this way (2 in a starboard bank and 4 in a port bank, and I always leave them switched together as one large 675AH bank).

Hope this seat-of-the-pants commentary helps a bit.

Bill
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Old 11-03-2007
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No one can give you any advice about your present system without knowing more about it and how everything is wired. Example: Perhaps the 4D is only for the power winch? Perhaps 4 of your 6Volts are wired to provide 24 volts to something. Perhaps one alternator is 24 V and the other is 12V. etc. etc.

Obviously even an ideal system is not possible to design until you know what hardware needs to be supported and driven and what you have on your engine and charging systems now.

My advice is to wait till the boat gets to you before you even think about this stuff.
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Bill- thanks, that's what I suspect I'll find when I trace everything and get it figured out. I would assume that one bank is for starting, probably the 4D, and the rest are house banks. In your system, is each bank switched, and you leave them all on Both, to make the one large bank? If, as you suspect, there are three house banks and one start bank with switches for all, does that seem like a reasonable way to set it up or should cables and switches be eliminated to form the one large bank? I've ordered Calder's book and I'm gathering info. on a lot of different systems so I can hit the ground running when the boat arrives. Thanks for your time, I appreciate it.

Cam- I realize that I am jumping the gun(going nuts with the boat 2700NM away), and maybe unfairly asking for ideas, but rather than getting into details I was more interested in the big picture - are four banks better/worse than three in general, should I eliminate addtional switches to only have one house bank and one starting? That sort of general layout ideas. There is no 24V on the boat, all 12V, except for 115V shore panel. Thanks, John
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Old 11-03-2007
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Here are a few principles I have gleaned, from replacing batteries and electrical systems on three sailboats in the past year. I agree with what has been posted so far
1. I agree that one house bank is better than two or three. Nigel Calder demonstrates the reasons why in his book, get the book as it will help you with other issues.
2. Generally simpler is better. If you tie the house bank batteries together purely with cables and don't use a switch to link them, there is one less thing to break and troubleshoot. Try to keep things simple in general as there is less to break, maintain and troubleshoot.
3. Use batteries of the same age, size and type in each bank. if the batteries are hard to access for service you will not keep up with servicing for the wet cells, also if you will leave the boat unattended for periods of time AGMs lose charge much more slowly. AGMs can be recharged much faster. Otherwise wet cells are a better value.
4. If one of these banks is in the bow (for anchor windlass or bow thruster) make sure you know how they get charged--most people charge them by connecting them to the house bank via battery switch. This means a long run of battery cables to the bow. In my opinion, if you have a generator and use it to charge the batteries, its better to run AC to the bow and run a separate charger there, but be sure that this charger is not powered by the inverter but by shore power/generator. Its easy to let these batteries go down by inattention.
5. Its very important to have a voltmeter for each bank, or some battery monitor like Xantrex for each bank, so you know if any bank is undercharged.
6. The alternator should be connected primarily to the house bank, and then to the starting bank with a battery combiner or something like that. The archives have many discussions of different kinds of combiners. Since you have two alternators, hook up the bigger one to the house bank. Make sure the alternator sensor wire is always hooked up to the battery or that you label the switch not to disconnect the battery or move the switch while the engine is running so you do not fry the alternator. Consider a Zap Stop diode to prevent frying the alternator. Consider a high voltage alarm for each alternator, they are not expensive and will prevent frying your whole electrical sytem, batteries, electronics and lights if your alternator goes berserk.
7. If your starting bank goes dead for any reason, you will find it useful to link together the house and start batteries. Easiest is a battery switch which you should label something like "use only to jump start" or you can use jumper cables. I myself keep an extra cable in the battery box to tie them together in such a circumstance, since its the cheapest and best connection. Takes me 5 minutes.
8. Clean contacts and terminals, use battery anticorrosion spray.
9. Label everything, make a checklist and post it. Its too easy to forget what the different switches are for, or get confused in an emergency, and to forget what you have to have on in order to do X. A list of where breakers and fuses are, the size of fuses etc. can be very helpful in troubleshooting. You can ensure you have an inventory of spare fuses that could be needed. Sometimes a fuse has been installed inline somewhere and if you find it now and put it in your list, this could be a godsend in an emergency.
10. Avoid hooking items up directly to the batteries, exception are sensors and bilge pumps.
11. Solar chargers should be hooked up at a separate terminal on the batteries from where alternator or other charging comes in. Consider a way to switch off while using other charging sources as voltage coming in from them can make alternator think the batteries are fully charged.
12. Verify everything, its amazing how often people use the wrong color battery cable (black on + line or vice versa) because it was at hand
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