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Old 04-14-2017, 11:53 AM   #1
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Noob Electrical system question(s)

I'm looking for some understanding...

I'm interested in beginning the process of buying a trawler and want to better understand the electrical systems. My only point of reference is my buddy's DeFever.

He has a setup that I see as logical, but confusing at the same time.

Starting batteries for twin Lehmans, and a Generator (i think - may be tied to house bank)
Single battery for the Windlass
Bank of 14 6v's (280Ah each) for house power
Magnum 2800 inverter/Charger

Options to Charge all these:
three alternators (one of the Lehmans has a second oversize alternator)
Solar panel (connected with a MorningStar unit)
8kw Generator
Shore power

So... here goes - what I believe to be my understanding:
I assume (yes, I know - NEVER assume because of what it does to you and me) that the 'standard' Alternators on the Lehmans charge their respective starting batteries, and that the Generator does the same for it's Starting battery.

The aux Alternator provides charging to the house bank when underway.

When on the hook, the solar panel provides a charge to keep the house batteries topped off - Wasn't designed to fully charge the batteries, just make sure she'll start

When at dock or under Generator, the AC power goes through the inverter to charge the battery bank.

So now to the questions:
Is it reasonable to think that all power requirements are pulled from the house bank, going through the inverter (for 110) and that all the other sources are simply there to charge the batteries?

Are the 'brains' of this all within the inverter/charger? Doesn't this make for a 'single point of failure'?

Can A/C be run just off batteries, or does the Generator need to provide that extra 'oomph'?

His house bank seems a bit excessive to me, am I wrong?

Is there a resource that I can visit/buy to better understand the nuances of boating electrical systems?

Sorry for the rambling, but wanted you to understand my only point of reference.

Thanks for any thoughts/feedback.

b
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Old 04-14-2017, 12:30 PM   #2
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Brian:

Boat electrical systems are complex and your buddy's Defever seems like it has a comprehensive system with multiple alternators, solar and a genset.

It is virtually impossible to discuss your buddy's electrical system over the internet. I can offer a few comments but the real answers depend on a detailed knowledge about how it is wired as there are many ways to set up a cruising boat. Get a copy of Charlie Wing or Nigel Calders electrical book for boats and read it from cover to cover. Then sit down with your buddy and talk through how it all works. He will also learn something I will bet ;-).

So here are a few comments to what you have told us about the Defever:

You are correct about how the inverter works. It is a combination inverter/charger so that when shore power or genset power is available it feeds the house batteries and charges them, but when there is no shore or genset power available it produces that power by converting DC to AC.

Moderate loads can be supplied by the inverter but any big ones like a water heater or air conditioner need to be supplied by the genset. The inverter usually can't be used simultaneously with the genset. It takes a very special inverter that syncs the frequencies to do that.

I can't really say that the inverter/charger is the "brains" as it has a few critical functions: charging and converting battery power to AC. But there are other "brains" like the solar controller or any battery combiners.

Are the house batteries too big? It all dpends on how long you want to sit without running the genset or hook up to shore power, what your loads are, how big the solar panels are and is it sunny or cloudy. In other words, impossible to tell.

Your buddy's boat is somewhat unusual with its second engine driven alternator. Most use the original alternator but maybe upgraded to a high output one with an external regulator for quicker house bank charging.

Good luck. There is a lot to learn about boat electrical systems. Most boats that you are likely to buy are not as well equipped as your buddy's. But if you know what you are doing, you can add systems to make whatever you buy functional.

David
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Old 04-14-2017, 12:35 PM   #3
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David,
Thanks for your interpretation! That helps! You've pointed me to a good resource. I'll get that ASAP!

With so many charging options and 12v vs 110 all those volts start swimming in my head, and suddenly become electrical chaos... you know, like "dogs and cats sleeping together" as Bill Murray would say.

thanks again for pointing me in a good direction.

b
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Old 04-14-2017, 12:57 PM   #4
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Brian,

Have a long discussion with your buddy. He should be able to answer and show you some of these things in person to help you understand.
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Old 04-14-2017, 01:01 PM   #5
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Quote:
Originally Posted by Brian_D View Post
...
So... here goes - what I believe to be my understanding:
I assume (yes, I know - NEVER assume because of what it does to you and me) that the 'standard' Alternators on the Lehmans charge their respective starting batteries, and that the Generator does the same for it's Starting battery.

The aux Alternator provides charging to the house bank when underway.
Probably true. Usually you see only one alternator per engine. The alternator often charges the starter battery with an echo charger to charge the house bank.

Quote:
When on the hook, the solar panel provides a charge to keep the house batteries topped off - Wasn't designed to fully charge the batteries, just make sure she'll start
More likely that the solar is charging the house bank since the alternator will keep the starter battery charged. Usually the starter batteries are isolated from the house bank so they can't be accidentally drained. There are also usually combiner switches that allow the house bank to be combined with the starter battery in the event of starter battery failure.

Also, in general, generator starter batteries are isolated - being charged by the generator's own alternator.

Quote:
When at dock or under Generator, the AC power goes through the inverter to charge the battery bank.
Yes.

Quote:
So now to the questions:
Is it reasonable to think that all power requirements are pulled from the house bank, going through the inverter (for 110) and that all the other sources are simply there to charge the batteries?
No - very unlikely. Much more likely is that when shore power or generator are enabled, all 120/240V circuits are energize from that source. All 12V circuits will be energized from the house bank.

There are rare exceptions. M/V Dirona (a Nordhavn 52) has a 240V inverter as well as 120V that can run all ac loads so that it can run from 60Hz shore power in other countries.

Quote:
Are the 'brains' of this all within the inverter/charger? Doesn't this make for a 'single point of failure'?
Not really. It's just one component. Without it you will lose the ability to charge batteries from shore power or generator, and you will not be able to run a/c appliances from batteries.

Quote:
Can A/C be run just off batteries, or does the Generator need to provide that extra 'oomph'?
Assuming you're talking about air conditioning - rarely is that run from inverters. The load is high and most battery banks wouldn't last long. On most boats you run the generator for A/C. There are always exceptions of course.

Quote:
His house bank seems a bit excessive to me, am I wrong?
You can never have too much battery capacity in your house bank .

This boat has 1960 Ah. I currently have 1250Ah and will go to 6V batteries when I change them out and go to about 1600Ah. Maybe the owner likes long weekends at anchor without having to run the generator.

Quote:
Is there a resource that I can visit/buy to better understand the nuances of boating electrical systems?
As mentioned Nigel Calder's book is a good start.

Quote:

Sorry for the rambling, but wanted you to understand my only point of reference.

Thanks for any thoughts/feedback.

b
I hope this helps

Richard
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