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Old 18-02-2015, 08:06   #1
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My quest for a quiet night - Inverter transiton for a power boat money question

I absolutely love the solitude of a calm quiet night on the water. Unfortunately, I own an aft cabin MY and have to run a generator to power all of the goodies.

On another forum, I was provided plans for a inverter set up which appears ideal for me especially since the plans are already in application on an identical boat.

I am looking at the following from the plans -

Xantrex SW 3000 inverter
(Six) GPL4CT 6V AGM batteries
140W solar panel
Solar modulator/ charger

From what I have been told, the above setup minus the solar panels will power everything on my boat for about 18 hours bringing the batteries down to 50%. With the solar panels I could probably get 24 hours out of it but sometime during the day I plan on running the generator for an hour or so just to be sure.

Here is the rub though. The inverter is around $1700 and the batteries are in the $1800 range for all six. Add the panels and the charger and I am looking at almost $4000 to do this project.

My wife (who will not go the sailboat route) thinks it's silly to spend that type of money since "we have a generator." Doing the math on the diesel fuel, I could run the genny for almost 1200 hours before the cost would be equal.

We spend the weekends on the boat and generally take 2-3 long trips a year.

Is there any other way to pull this off cheaper? The batteries and inverter will be underneath the saloon couch so no fear of water exposure.
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Old 18-02-2015, 08:15   #2
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

If you went for lead acid golf cart batteries, that would halve your battery costs. Secondly, is there any scope for reduction of consumption? LED lighting, etc.
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Old 18-02-2015, 08:22   #3
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

I thought about lead acid but since the batteries are going to be underneath the seat would there not be an off gassing problem?

For the power consumption I am just going off of what the other forum member provided that worked for him. That includes running the fridge, freezer, stove the air conditioner(s), etc.
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Old 18-02-2015, 08:31   #4
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

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Originally Posted by k9medic View Post
I absolutely love the solitude of a calm quiet night on the water. Unfortunately, I own an aft cabin MY and have to run a generator to power all of the goodies.

I am looking at the following from the plans -

Xantrex SW 3000 inverter
(Six) GPL4CT 6V AGM batteries
140W solar panel
Solar modulator/ charger

From what I have been told, the above setup minus the solar panels will power everything on my boat for about 18 hours bringing the batteries down to 50%. With the solar panels I could probably get 24 hours out of it but sometime during the day I plan on running the generator for an hour or so just to be sure.

Here is the rub though. The inverter is around $1700 and the batteries are in the $1800 range for all six. Add the panels and the charger and I am looking at almost $4000 to do this project.

Is there any other way to pull this off cheaper? The batteries and inverter will be underneath the saloon couch so no fear of water exposure.

Might depend on what means "all the goodies."

Lead-acid batteries could save you some money. The trade-off might be about off-gassing (LA) versus not as much (AGM) in your saloon. (I'd go with AGMs or gels in that location anyway, though.)

If you stay with AGMs, you might compare costs, sizes, Ah of the six 4CTs to four 6CTs or even L16Ts.

How do you cook? If that's electric, you might be running the generator 2x/day anyway? If so, you might easily do without the solar. (FWIW, we're all-electric -- not counting the portable propane grill outside -- with two fridges, water heater, etc... and we run the genset 2x/day while cooking, works fine.

Maybe compare all your cost projections to the cost of a comfortable pair of ear plugs.

Edit: Ah. Our posts crossed; now I see you're including AC, and that you've already pondered the LA vs. AGM question. We've solved the AC question by simply not anchoring out when it's a bazillion degrees out and humidity is over the moon... A bunch of DC fans spread around, plus natural ventilation, generally works for us; if not, we can enjoy an occasional marina cheaper than an inverter setup.

-Chris
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Old 18-02-2015, 08:40   #5
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

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If you went for lead acid golf cart batteries, that would halve your battery costs. Secondly, is there any scope for reduction of consumption? LED lighting, etc.
Doesn't flood acid also limit the discharge %?

For the OP, do you not run your big engines at least once a day? Do you not have an alternator that could charge the house bank? If you are already using your engines for any length of time, that seems like a more sensible set up than a generator.
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Old 18-02-2015, 09:03   #6
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

I don't think you are going to be able to run the A/C's on the inverter. Even if you could, along with the other stuff the amp draw would be pretty high. I think you should do the math on your amp draw. My guess is, your proposed setup would be fine-minus the A/C's. I think you would be better off spending a fraction of that money on a good sound enclosure for your genset and let it run...
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Old 18-02-2015, 09:06   #7
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

I would most likely run my big engines only when traveling to a new location.

Looking at the diagram that was sent to me, these new batteries are independent. Am I reading the diagram wrong?



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Old 18-02-2015, 10:07   #8
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

I don't think I'm seeing a battery there. What's the blue thing? Distribution panel? (Can't quite make out the labeling.)

Good points about sound shield and LEDs. Is you genset already in a box? Or not? Have you already swapped out all you incandescent lights to LEDs?

-Chris
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Old 18-02-2015, 10:18   #9
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

I strongly suggest, rather than using someone else's claimed consumption, that you calculate or measure your own. Otherwise you might be in for a big disappointment. My main worry is the A/C. What's an A/C, 1kW? Over 12 hours, you'll use 12 kw/h, plus inefficiencies in the inverter PLUS the rest of your electrical items. You'll need enough batteries to draw them down to 50%.
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Old 18-02-2015, 10:29   #10
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

Why do you need to run your gen at night? Maybe find a solution for that.
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Old 18-02-2015, 10:38   #11
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

I'm planning on doing the math as well but this particular plan is in place and working on an identical boat so it is a good starting point.

I don't want to run the gunny at night, especially in an anchorage that is surrounded by sailboats.

The blue item in the diagram is the inverter itself. I may have gotten lucky as I just located a xentrax sw 3012 locally for a great price.


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Old 18-02-2015, 10:55   #12
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

Several comments.

You will not be able to run the air conditioner on your system. It would take ten times the battery capacity you mention to run a/c for overnight. For the other stuff an inverter would probably be OK.

Also, the inverter size you list would probably choke on the startup load for the air con. When the a/c first starts up and the compressor kicks in the power draw can double until it starts turning.

I would steer clear of Xantrex. Lots of problems reported by users in recent years along with poor customer support.

AGM batteries are must more expensive than lead acid and much less tolerant of abuse. If you discharge them too much for too long and do not regularly recharge them completely (several hours of charging) they will very probably die an early death. They are not better than lead acid for discharging to a lower state. The biggest advantage of AGMs is they can take more charge, faster.
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Old 18-02-2015, 10:57   #13
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

First off, if you could reduce the number of "goodies" then maybe you wouldn't need to run the genny all night long. Second, if you really do have to run the genny, then a pair of earplugs will cost you about 5 cents and will take care of all the disturbing noises, not just the genny.

Sometimes the simple solution is the best.
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Old 18-02-2015, 11:38   #14
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

Helping you would be easier if we could see a diagram of your DC system.
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Old 18-02-2015, 11:39   #15
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Re: My quest for a quiet night - Inverter transiton for a power boat money question

No reasonable battery bank would run our air conditioning all night.

We have inverter, 8 golf cart batteries, 5 kw genset. 120v apartment sized refrigerator. TV, ect. If not moving the boat and not using A/C we need to run the genset 1-2 hours a day depending on TV usage. Usually less than 1.5 hours. We have two 12,000BTU air conditioners. We are changing to LED lights a few at a time as we can. First one to change is the anchor light as it stays on all night.

They way we handle hot sticky nights: We usually have dinner and run the genset while watching a movie. During this time we close up the boat and run the air conditioning to pull the temps down and dry out the boat. This tops off the batteries at this time also. We shut down the a/c and genset at bed time. I'm old enough that I need to get up around 2am anyway and by that time our bodies are cooled and relaxed and it is usually feels fine to open the boat and maybe run the 12 volt fans.

I keep looking at solar panels and will spring for some eventually. If you can vent the battery bank you could buy 8 six volt Duracell golf cart batteries from Sam's Club for around $750. That is 800+ amps in rugged batteries.
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