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Old 20-01-2007, 10:29   #406
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Not being an electrical engineer, much of this recent discussion goes over my head. Would one of you be so kind as to dumb it down a bit and give me an interpretation?

RE: Miami, yes, my wife and I will be attending. Anyone else?

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Old 20-01-2007, 12:14   #407
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ID,

I will try to explain my concern about damaging the house batteries with an examle.

Think of your house batteries as a reservoir of water. At one end of the pond water is coming in and at the other end you regulate its out flow. Think of Lagoons 600 watt house battery chargers as the stream that continually fills your pond at the rate of 6 gal./minute. At the other end we will let your 1800 watt inverter (for AC needs) stand for a drain on the pond of 18 gal./min. This is the max. drain for AC appliances such as water heater, hair driers, or a micro, so when ever they are running your pond is being drained at a rate of 18 gal. min and refill at only 6 gal./min. Just 1 hair drier running will be drain your pond at 18 gal./min., and will require the full output of your inverter, and hot water for showers will drain your pond at the rate of 20 gal./min. With the Lagoon 1800 watt inverter, you will only be able to do 1 thing at a time, no hair driers could run while someone else is in the shower, as this would be twice the inverter capacity.

But there is also going to be a drain on the house batteries for the DC chores, such as house & running lights, windlass, fridges and freezers, instrument,and pumps. At anchor these will add up to at least another
1800 watts (and probably more), or another 18 gal./min. of water leaving the pond. That's 6 time more water leaving than is being replaced. How long before the pond is down 40% and causing all your fish to die, will depend on how big of pond you stated with. In our case how many Amp-Hours of battery storage we have in the house battery system.

My concern is that there is that Lagoon has nothing monitoring the status of the house batteries, and they could easily be over discharged, which would shorten thier life greatly.

That is why I will draw my AC power fron the Motor Batts, as they are constantly being monitored for discharge, and the genset will come on automatically (at 20 to 40 DOD)to protect them from being over discharged.

My boat has to be somewhat idiot proof because it will be going into charter.

I would love to go to Miami, as I have tried twice before to get a sea trial demo, only to be denied at the last minute! I would also like to know what changes have been made to the boat I was on in Lauderdale in Dec., to see if it would be worth my while. Like a new railing up to the helm, the new higher davits, or the 2 new post added to the hardtop bimini.

I hope the above example helped to convey some of my concerns with Lagoon's inverter setup.

Fair Sailing _(\_
Quiet Riot 420
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Old 20-01-2007, 12:25   #408
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Have you had it confirmed that the 25A rating for the 72V->12V chargers is measured at the 12V end? If it was at the 72V end then you'd have 3.6kW.

To extend your example a little further though. Let's say you had a 1.5kW hair dryer running for 5 mins on the standard house inverter (and assuming the DC/DC charger is only .6kw). That means your net draw on the house bank is 0.9kW (1.5-0.6) for 5 mins. To recover that from the motor battery banks would take a further 7.5 mins before your house banks were fully charged. (Further assumption that nothing else is running). I am hoping we won't be rushing around so much that we won't have time to replenish what we use.

Presumably it wouldn't be too hard to put instrumentation around the house bank to measure the reserve.

I'd be very interested to compare notes at a later date. I can see why you are doing what you are doing but I don't feel compelled to follow suite.

Have you also looked at solar / wind power to top up the house bank? My plan is to measure our demand during the first few months of our cruise and size my alternate energy inputs based on what we learn.
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Old 20-01-2007, 13:43   #409
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A little more arithmatic. Correct me if I'm wrong.

Lets say I fully load the 1.8kW inverter. With .6kW coming from the engine batteries my net drain is 1.2kW. With 2 140Ah 12V batteries, it will take 33.6 mins to drain the house bank down to 80%.

If I stop there, with no other load on the batteries, it'll take 67.2 mins to fully recharge. Put it another way, I can draw a full load for 33 mins out of every 100 without ever taking the house batteries down below 80%. If I need longer sustained periods, I add more house batteries.

I'm glad we're having this conversation though as I didn't realize the house batteries had no instrumentation. I will want to fix this at some point.
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Old 20-01-2007, 14:39   #410
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Steve,

As far as the 25 Amp rating is concerned, I can zoom in on my picture of the 2 units and clearly read the label. It reads ENAG CCDS2 72V-12V/25A, input 60 to 120Vdc, output 13.7Vdc/25A. Remember when doing your calulations that these units are probably not better than 85 to 90% efficient when running much of a load.

I will study your numbers a little more, and see if I get similar results. I do think you might want to consider a 4 battery house bank to be safe. I just zoomed in on one of my pics of the breaker panel, and sure enough the 4 position digital readout display was showing the "Domestic" battery level at 13.2 V, so this is where you will have to keep an eye on the voltage in the house batts.

If you would like I can e-mail you the pics.

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Old 20-01-2007, 14:51   #411
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Thank you, that is helpful. But, it sounds like there is some confusion (or lack of specificity by the factory) regarding the size of the 72 > 12 volt charger(s). One document says there is 1-40 amp charger, another says there are 2 - 25 amp chargers. Also, whether the amperage is being measured at 72v or 12v. Sounds like this last issue is a major one and makes a lot of difference.

On my option sheet, there are places for (1) upgrading the 40 amp charger to 80, and (2) adding two more house batteries. When discussing these with my dealer, he advised against them, saying that with other changes Lagoon has done, that they aren't necessary. Are you saying they are, at least for the kinds of loads you are describing? It also sounds like the other option is to do as has been described, adding 72 v to 110 AC inverter(s). On my option sheet, Lagoon listed one (a 3000), but at over $8K.

What are you advising?

Thanks.

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Old 20-01-2007, 14:56   #412
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Quote:
Originally Posted by Quiet Riot 420
If you would like I can e-mail you the pics.
Quiet Riot 420
Yes please. Thank you in advance.
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Old 20-01-2007, 15:04   #413
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ENAG chargers

Quote:
Originally Posted by Quiet Riot 420
It reads ENAG CCDS2 72V-12V/25A, input 60 to 120Vdc, output 13.7Vdc/25A.
Is this the range? http://www.enag.fr/W/upload/article246_FC-CDS2-AN-A.pdf
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Old 20-01-2007, 15:41   #414
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Originally Posted by Intentional Drifter
What are you advising?
This depends on the type of demand you intend to put on the system. Remember, when you do run the genset, particularly with the larger one, you can use the surplus energy to heat water, fill tanks, etc.

I'm convinced the larger genset is the right idea. The rest I just can't predict so it's going to be down to real life experience and possible tuning.
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Old 20-01-2007, 15:57   #415
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[quote=Intentional Drifter]

On my option sheet, there are places for (1) upgrading the 40 amp charger to 80, and (2) adding two more house batteries. When discussing these with my dealer, he advised against them, saying that with other changes Lagoon has done, that they aren't necessary.

As to the optional two house batteries, I was also so advised. The rationale being that the house bank was connected to one of the propulsion banks via a DC-DC converter. Does anyone know if this is accurate information.

As to charger upgrade, does anyone know the pros and cons other than the obvious pro that the batteries would charge faster, at least initially.

P.S. IMHO it's nice to see that we are finally focused on the 420 specifically rather than generic design philosophy/issues. Don't get me wrong, some discussion is good, but when it goes on ad nauseum, its time to move on.

Also, in reply to QR420's query, I will be at the Miami show beginning Sunday, February 17.....if anyone wants to hook up sometime in the afternoon, it would be my pleasure to meet you and buy you a drink
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Old 20-01-2007, 16:09   #416
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In case you haven't notice, Catamarans.com posted a new price list. This is sort of like tracking my investments. My boat, as ordered in March, would cost over $136K more, if ordered today. That's a 32% increase in 10 months. Sure wish my retirement account could do that.

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Old 20-01-2007, 16:09   #417
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The way I'm looking at it is :
Adding extra house batteries extends the period of time you can draw high power from the inverter.
Adding extra DC/DC chargers (if this can be done) would reduce the time interval between peak usage.
Adding extra house batteries will also give you more Ah but compared to what you have sitting in the motor batteries, percentage wise this is not significant.
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Old 20-01-2007, 16:44   #418
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Mike,

The newest price sheet that I have seen doesn't have the 40 amp standard and an upgrade to 80 amps as an option available any more. They are going to use 2 x 25 amp units with no upgrade, but if you could get more 25 amp units say 2 more, a parallel install looks easy. This would give you at least 1200 watts of charging power.

Fair Sailing _(\_
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Old 20-01-2007, 20:29   #419
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Back Up Generator

I would guess that I am not alone when it comes to not feeling totally comfortable with relying exclusively on the one generator.

So, have any of you electrical professors figured out the minimum size for a back up generator to run the two 25 amp battery chargers....would a 5K do the job?
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Old 20-01-2007, 20:35   #420
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I look at regeneration as backup to the generator. If my genset packs in during a passage then I'll initiate the prepared strategy to build and conserve power levels in all the batteries so I have plenty of juice in the event it is needed for mooring, etc. This will mean losing what's in the fridge if we become becalmed and only consuming what we're making.
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