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Old 17-02-2010, 15:43   #1
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Design Problem - Electrical System Upgrade

Our boat, acquired last fall, is a Moody 54. She has the following electrical equipment:

1. Two 24-volt service banks consisting of 4x of 110ah x 12v leisure batteries each, making two banks of 24v x 220ah each. Engine and generator start circuits are both 12v and completely separated from the service banks (own 12v alternators, own charger, etc.).

2. One bank (called "service") runs winches, windlass, pilot, bowthruster.

3. Another bank (called "domestic") run lighting, pumps, electronics.

4. 6.5kW Kohler generator.

5. 100 amp x 24v Leece-Neville alternator charging both service banks through a Driftgate "electronic charge splitter" (whatever that is).

6. 35 amp x 24v Sterling "Phase Three" charger charging both service banks through an internal splitter of some kind.


This system does not work as well as it could. The main problem is that the "domestic" battery bank doesn't last more than a few hours at anchor under our typical loads (2x refrigeration, lot of halogen lighting, electronics). The battery charger is not big enough (35 amps) to recharge the "domestic" battery bank in a reasonable amount of time. So we end up with frequent and long generator runs while at anchor or on a pier with no power.

It seems to me that there are two big problems and a couple of minor ones. The big problems:

1. "Domestic" bank too small for the boat, at 220 amps x 24v

2. Charger too small at 35 amps for 440 ah of batteries.

Other problems:

1. Too much energy consumption

2. Unregulated alternator probably not getting all the charge it can into the batteries.

3. There is no inverter on board.

And a big question:

1. Does the "service" bank really need to be separated from the "domestic" bank?


What we are thinking:

A few people here and elsewhere have advised combining the "service" & "domestic" banks. They are separate probably (a) to isolate electronics from shocks of big loads like winches, windlass, thruster; (b) to reserve battery capacity separate from domestic loads, to ensure there is always enough power for pilot etc.

So we are somewhat cautious about just blithely combining them. Three alternatives: (a) add a couple more 110ah batteries to the "domestic" bank; (b) divert a couple of 110ah batteries from "service" to "domestic"; (c) provide a combining switch (an "A", "B" or "Both" switch) between domestic and service banks, to be used at anchor when there are not service (winches, windlass, thruster) loads.

What do you guys think?

To address the other problems:

1. If the banks are kept separate, leave the 35 amp Sterling charger on the "service" bank, and install a new larger charger (better, a combo charger-inverter) on the "domestic" bank.

2. Install some kind of external regulator on the big 24v alternator (maybe something like the Sterling alternator-driven four-stage battery charger).

3. Tackle energy consumption as well as possible (starting maybe with LED cabin lighting).


I am not made of money and after an incredibly expensive first half-year of ownership I want to keep the cost of upgrading the charging system to some reasonable limit -- this is, after all, not a safety or mission-critical issue (it boils down to reducing generator run time, actually). But within the limits of reasonable expenditure of course I would like to improve and if possible optimize the situation.

What do you guys think?

And what about choice of charger/inverter? I really like the Victron Multis and Quattros, with their ability to program limits on shore power and generator power, and especially their nifty power-boost feature, which can make up momentary heavy loads (like a/c starting up) with inverter power. But they are $$$$, about $3500 (ouch!) for the Multi with 70 amp charger, and even more for the Quattro. I could get a simpler 50 amp charger/inverter from Sterling or others for less than half that.

Or I could even skip the extra charger this year. With more usable battery capacity (obtained through adding, diverting, or combining battery capacity) I could store more of the abundant alternator power while motoring, and charge less from the generator, and save my pennies until next year.

What do you guys think??!! I bet I'm not the first sailor to agonize over this kind of question.
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Old 17-02-2010, 17:18   #2
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No, of course you're not! Every sailor deals with this sooner or later.

The first thing you need to do, IMHO, is to develop a detailed electrical budget. You'll no doubt like this, because it's something you can do in the wintertime and something which doesn't cost anything...except your time and brainpower. But it's absolutely essential to provide the data required to make an intelligent decision.

It could very well be that the existing system is fine, or nearly so. Maybe the batteries have lost capacity thru plate sulfation or other reasons. If so, that could account for your short-time experiences with the house load. But, until you have a very detailed idea of what you're actually using, you won't know for sure.

Once you have the electrical budget, you'll have the basis on which to do further analysis. Then, some appropriate measurements (amperage draw, charging rates, battery condition, etc.) will point the way to the future.

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Old 17-02-2010, 18:32   #3
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Thanks. The batteries (all 10 of them, including engine and gennie start batts) were brand new when I bought the boat. Varta leisure batteries, nothing fancy.

I'm still refining the electrical budget but with 28x 10 and 20 watt halogen bulbs in the accomodation, innumerable smaller light bulbs, two largish refrigeration units, computers, electronics, stereo, and so forth, 220 ah (giving 110 ah practical capacity, or maybe even 88 ah if you accept the idea that you shouldn't count the last 10% either, besides the first 50%) is little. It's 2112 watts for one hour, at 24v. LED cabin lighting will help a lot (plus shutting off the freezer most of the time), but I reckon we still won't get through a day at anchor without some kind of capacity boost, and when the batteries are down we will have to run the generator for hours with the present small charger.

I don't have a battery analyzer on board -- just a simple voltmeter -- so hard to take any meaningful measurements. But I take your point and maybe a reasonable first phase will be to install battery monitors and check real consumption rates under different conditions.
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Old 17-02-2010, 18:39   #4
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The first thing I notice is that you are not calculating your amp hours correctly. when batteries are in series, you double the voltage but not the amp hours. So two 12 volt 110 AH batteries in series is 24 volts but only 110 AH. That could be part of your problem. You would probably benefit from a larger charger also. As Bill said above, figure all of your normal loads, your "budget", then you can see if the battery bank is adequate.
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Old 17-02-2010, 18:45   #5
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The first thing I notice is that you are not calculating your amp hours correctly. when batteries are in series, you double the voltage but not the amp hours. So two 12 volt 110 AH batteries in series is 24 volts but only 110 AH. That could be part of your problem.
Sorry, but each bank consists of 4 x 110 AH x 12v batteries. Wired in pairs to provide 24v each bank does produce 220 AH x 24v. So there is a total of 440 AH x 24v on board (eight x 110 AH x 12v batteries) not counting the starting banks, equivalent to 880AH on a 12 volt boat.

This would probably be enough IF the two service banks were combined (the "domestic" bank is mostly loaded at anchor or at nigh; the "service" bank is only loaded when underway -- so the loads are synergistic). That's the appeal of just combining the banks, which has been suggested.
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Old 17-02-2010, 19:19   #6
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How about testing the individual batteries with a capacity checker? Maybe you have some sulfated batteries?
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Old 17-02-2010, 19:30   #7
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Quote:
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each bank does produce 220 AH x 24v.
So you should be able to recharge them by at least 55A 24V.

Quote:
Originally Posted by Dockhead View Post
6. 35 amp x 24v Sterling "Phase Three" charger charging both service banks through an internal splitter of some kind.
Is that 17.5A per bank?
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Old 17-02-2010, 19:37   #8
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Pretty boat, congratulations.

I think I would start by looking at the fridge and ap. The windlass and thruster only run when the propulsion engine is running. Winches use little power, they simply don't run enough.

We're set up about the same, the 24 bank is 380 ah. The house is 520 ah. We charge with 40 amp * 2 to the 12 v bank and 50 amp or so into the 24 bank. On the hook we charge with a 5 kw generator through both chargers. Our fridge is a cold plate so we only cycle it when the generator is running. I doubt we are topping up everything by running the generator 2 hours a day but I haven't done the math. With the propulsion engine we can top up pretty quickly with two large alternators.

I think I would work on the conservation side first then if there are no gains left look at generation.
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Old 17-02-2010, 21:55   #9
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So you should be able to recharge them by at least 55A 24V.



Is that 17.5A per bank?
Only if both banks are deeply discharged at the same time. Because of the different nature of the loads, that will usually not be the case. The charge splitter can direct nearly all of the charge capacity into the domestic bank, but it's still pretty wimpy. If it works at full rated capacity (fat chance) during bulk phase, I will get only 13% rated capacity of the bank back per hour of generator running. Not too good.
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Old 17-02-2010, 22:03   #10
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Pretty boat, congratulations.

I think I would start by looking at the fridge and ap. The windlass and thruster only run when the propulsion engine is running. Winches use little power, they simply don't run enough.

We're set up about the same, the 24 bank is 380 ah. The house is 520 ah. We charge with 40 amp * 2 to the 12 v bank and 50 amp or so into the 24 bank. On the hook we charge with a 5 kw generator through both chargers. Our fridge is a cold plate so we only cycle it when the generator is running. I doubt we are topping up everything by running the generator 2 hours a day but I haven't done the math. With the propulsion engine we can top up pretty quickly with two large alternators.

I think I would work on the conservation side first then if there are no gains left look at generation.
I don't know what kind of boat you have, but you have half again the battery capacity and double the charging capacity. I am pretty sure that conservation is not going to get us nearly far enough.

Your point about the momentary use of winches, windlass, and thruster underlines the inefficiency of separated banks. The "service" bank is hardly worked; the only big continuous load on it is the pilot. In your case, you have no choice of combining them, because of the different voltages. In our case, everything is 24v so we could combine the banks.

Hmm.
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Old 17-02-2010, 22:15   #11
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Sounds like you have a job cut out for you. Seems to me that doing this on the cheap will not give you the results you want.
First as Bill said, develop a energy budget. Find out for sure what you are using.
Next check out each battery and make sure they are ok. Never heard of the brand you have. Are they wet cell, agm or gell? If wet, test each cell with a hydometer. Check each for proper fluid levels. When is the last time you equalized?
Next, you need a good battery monitor. The victon unit looks good, and is easy to install. There are others. You could get a link 10 for minimum on ebay I bet.
This will show what you are using, and how fast you are discharging.
Next would be to combine the house and the windlass bank into one bank. That will double your capacity on the house side. The windlass and thruster should not be run unless the engine is running anyway.
Then go over each item on board and see what you can do to improve its electrical usage. Change light bulbs to florecents or led for instance. Cut out the freezer for now. Watch laptop use. etc. Untill you get a handle on it.
Then figure out a way to generate more. That means solar, wind and or towed generator. ChaChing.
Finally, your charing system needs as you know upgrading.
The victron units are very good. And not much more than the xantrex. Better product. The phoneix multi 3000 watt inverter has 120 amp charger and is around 2400 USD.
Then look at upgrading your alternators to a larger one, if your battery bank can take it. 160 amp x2 with good regulation.

It is distressing how hard it can be to power a modern yacht. With all we put on it, and ask it to do, in a very harsh marine enviroment. Some times we ask to much.
Its not impossible, cause others do it, but it takes planning and money.
Also, cheap batteries are not the best, imo. Think about upgrading to good marine batteries. With your boat and setup, you will be more satisified.
Good luck.
Bob
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Old 17-02-2010, 22:18   #12
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I don't know what kind of boat you have, but you have half again the battery capacity and double the charging capacity. I am pretty sure that conservation is not going to get us nearly far enough.

Your point about the momentary use of winches, windlass, and thruster underlines the inefficiency of separated banks. The "service" bank is hardly worked; the only big continuous load on it is the pilot. In your case, you have no choice of combining them, because of the different voltages. In our case, everything is 24v so we could combine the banks.

Hmm.
I believe he said both banks are 24v. The starting bank for the engine and genset are 12 v.
He has a moody 54.
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Old 18-02-2010, 00:48   #13
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Why 24V when 12V is used?

If I understand your situation correctly you have 24V battery charging and use 12V.

Surely it would be better to convert everything to 12V? Would this be that difficult?
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Old 18-02-2010, 02:29   #14
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If I understand your situation correctly you have 24V battery charging and use 12V.

Surely it would be better to convert everything to 12V? Would this be that difficult?
No, the entire boat is 24v except only starting (engine & gennie), VHF, and the sounder I believe.

There are four different banks, actually -- "domestic" (whole house) 24v x 220ah; "service" (winches, pilot, windlass, thruster) another 24v x 220ah; engine starting, 12v x 110ah, and generator starting, 12v x 80 ah.

The main engine has two alternators -- a big 100 amp 24v charging the "domestic" and "service" banks through a splitter, and a smaller 12v alternator charging the starting battery. The generator has a small 12v alternator charging its starting battery.

I'm happy with 24v and I'm glad that the starting batteries are completely separate with their own alternators and chargers; the basic problem is lack of house capacity and very long generator runs required to charge on the hook.
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Old 18-02-2010, 04:55   #15
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Your generator can produce 56 amps at full load so you have 28 amps per bank given no losses. The charger outputs 35 amps per side so it looks big enough.

Maybe add a switch so you can tie the banks together when not charging then disconect when charging?

Maybe belt a larger (180~220) high amperage alternator to the main engine so you can dump big amps in when needed?

I agree with Bill, do an energy management worksheet to determine what you're using.

Ice cubes are truly energy hogs.
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