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Old 10-12-2007, 14:48   #16

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And... you need an isolation transformer to do what you wish:

Marine: Isolation and Boosting Transformers

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Old 10-12-2007, 16:34   #17
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Originally Posted by ssullivan View Post
If you're a dockside dandy or a solar panel/wind guy that would be true. If you run a genset, like I do, the above statement is quite false.

Again, not sure I agree:

Jack Rabbit
I don't think I totally agree with your comment about the genset - which I do have. I don't plan on spending a whole lot of time dockside while cruising, but I'd like the system to be as flexible as possible. My wish is to run the genset for as short a time as possible. And I will supplement battery charging with solar panels and probably a wind generator as well. When running the genset, I'd like to charge the house bank as quickly as possible - so that means "blasting" the bank at about 35-40% of its capacity, assuming AGMs, and that the charging is temperature-compensated - which the Iota DLS chargers at JackRabbit Marine do not support. There is an option to convert them to a 3-stage charger, but there is no mechanism for sensing battery temperature. I've already talked to JackRabbit Marine, and they recommend against the Iota chargers for my intended application.

My plan is to eliminate the need for separate isolation transformers by utilizing the isolation transformers built into the battery chargers. By running the boat's entire AC loads off the genset and/or inverter, my intent is to not have to worry about conversion of 50Hz AC to 60Hz - basically accomplishing a universal shore-power capability for charging and running large AC loads off a large inverter or stacked smaller ones. What I haven't done yet is do the economic comparison to see if it's worth it. What I haven't found yet is pricing for a separate isolation transformer and 50/60Hz conversion.

I must not be explaining things completely - leaving things out in individual posting. I'm basically following the tenants espoused in Nigel Calder's and Charlie Wings books on the subject. I'll post a PDF version of a schematic drawing of the AC side of the boat when I finish it (hopefully tonight). Perhaps seeing it will give you a better idea of the planned system, rather than what I'm saying. A picture's worth a thousand words - so when you see the picture, you can really tell me where I'm going wrong!

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Old 10-12-2007, 17:31   #18
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Here's the diagram. It's adapted from figure 9.21 on page 172 in Charlie Wing's book, "Boatowner's Illustrated Electrical Handbook", 2nd edition.
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File Type: pdf Beausoleil Drawings - AC Schematic Opt 4.pdf (49.8 KB, 120 views)
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Old 10-12-2007, 17:47   #19
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Looks very complicated.

I hope that you are not planning to wire everything up and flick a switch...
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Old 10-12-2007, 20:17   #20
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For what it's worth. I had a similar idea about using the inverter to power everything. Here's where I ended up with our design. Use the Mastervolt battery charger to charge from US or Euro power. Use the inverter for the Washer/Dryer and a small Aircon 5200Btu (Master Stateroom only). We could run one or the other but not both off the inverter. We have two 110Amp Mastvolt alternators that could charge batteries while running the Aircon OR the Washing Machine. We selected a Mermaid AirCon 16KBtu that works both in USA on 220-60 and in Europe 230-50 power so that it would never be run off an inverter or Genset since we won't have or want one.

Since we are designing the system from scratch, the big issue was Aircon and batter charing at the doc worldwide. We spec'ed 600AH 24V, 4 solar panels, wind generator, possibly water generator. Man, writing this down makes me want to rethink and simplify.....
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Old 10-12-2007, 22:42   #21
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having 66% reserve rather than 50%.
Interesting and I guess they have their reasons. But the 50% line is what has become an "industry rule of thumb" of price vs longevity of batteries. In other words, it becomes the most economic use of the life/power/cost of the bank. If I can explain it in a better way, Once you start to discharge a battery, it's loses some of it's life, never to come back again when recharged. It's gone for good. Eventually enough life gets removed making the battery useless to us. The further you discharge a battery, the more of that life is removed. I have found that start batteries will handle 3 compleate discharges and they are dead for ever. Like leaving your car lights on for instance. For a deep cycle battery, the 50% mark is considered the best cycling rate to get the optimum life from the battery, vs getting power. I am still not sure that made sense.
OK, now to charging. Yes you are right about thumping current back in to a bank with temperature monitoring. Yoy can really hit the bank hard as long as the temp stays low. But this is where I believe you may come unstuck. The reason why I am harping on about the bank being too big, is the ability to rapidly charge. If you really do want to get 35 to 40% back in, then you need a 350A-400A charger with the 1000Ah bank. That is serious power and I don't think you will find a charger capable.
So the goal is to try and find a balance. A bank big enough to meet the consumption needs and yet small enough to allow you to recharge as quickly as possible.

In relation to the Isolating tx Sully was talking about. To correctly wire an invt/chgr means that you will have the mains earth connected to your boat DC earth. This then leaves you susceptable to galvanic corrosion between boats connected to the shore power also. Not so much an issue when on the hook of course. But if you are connected to shorepower, you need to isolate the earth in saome safe way. This can be done by using an Isolating Tx or by using a Galvanic Isolator which breaks the earth in normal circumstances, but allows current to flow in a fault condition.
However, I see you have one in the diagram.
Good circuit by the way. Only one very nitpicky point. The DC earth on the Generator needs to be taken to DC earth on the main engine. The AC earth Bussbar is then connected to DC earth at that same earth point on the engine. This eliminates "earth loops"

I think you are on the right track running your equipment from the inverter to eliminate the freq and voltage differences.

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Old 19-12-2007, 08:50   #22
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The simple thing would be to decide on a base inverter AC feed (shore power say 120 V 60 Hz.

Install a transformer on one shore power plug to convert 208/220/240 to 112/120/130 either 60 or 50 hz.

Or the otherway around...

Install a switch to allow base AC to feed the inverter, and the boat direct or just the battery charger.

The difference in frequency will only change the operating speed of the AC induction motors (faster on 60 Hz). (You don't have to select direct feed.)

50 Hz motors can operate at full load on 60 hz but 60 hz motors on 50 hz power may overheat if fully loaded.

Just about everything else doesn't care.

You will need two shore plugs High voltage and Low voltage with some cheaters. and your good to go.

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