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Old 01-02-2015, 10:44   #16
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Re: Best generator for day-in/day-out use?

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Originally Posted by melissiti View Post
We're in the UK, it's AC and presumably 50Hz?
If your system is other than 50 Hz you would be the only one in the UK.

If you are buying locally then of course you will be getting the proper generator for your boat and all the equipment on board. If you travel to some foreign locale where they use that funny 60 Hz stuff you may need to make some adjustments. However, as travellerw mentioned, a lot of electrical stuff these days will work on any flavor of electricity but don't assume that is the case for everything.
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Old 01-02-2015, 10:53   #17
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Re: Best generator for day-in/day-out use?

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Ah, the Onan site had a better calculation tool - looks like we're gonna want 6-8kw
I might have missed it but I don't see any comment about whether your boat is set up for petrol or diesel. Can make a difference in the decision making process.

If you are running diesel you should consider that diesel engines are happier and live longer if they are run under a good load. If you buy a diesel generator large enough to run every electrical device on the boat all at once then very likely there will be times when it is running just to power a few lights so very little load at all.

A little of this is no problem but if you do it a lot it could shorten the life of the generator and possibly cause it to run poorly.

Instead of buying a generator for the maximum possible load you can buy a smaller (and lighter and cheaper) generator and just take a little care on what's all running at the same time. Don't run an electrical stove, room heater, calorifier and clothes washer/dryer all at the same time.

If you are on petrol then not so much of a concern.
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Old 01-02-2015, 11:07   #18
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Re: Best generator for day-in/day-out use?

Awesome, thanks, that's what I thought. So about 4 kW is probably optimum for us, then? (although obvs I'll double-check that!) We're Diesel.
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Old 01-02-2015, 11:08   #19
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Best generator for day-in/day-out use?

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Originally Posted by skipmac View Post
I might have missed it but I don't see any comment about whether your boat is set up for petrol or diesel. Can make a difference in the decision making process.

If you are running diesel you should consider that diesel engines are happier and live longer if they are run under a good load. If you buy a diesel generator large enough to run every electrical device on the boat all at once then very likely there will be times when it is running just to power a few lights so very little load at all.

A little of this is no problem but if you do it a lot it could shorten the life of the generator and possibly cause it to run poorly.

Instead of buying a generator for the maximum possible load you can buy a smaller (and lighter and cheaper) generator and just take a little care on what's all running at the same time. Don't run an electrical stove, room heater, calorifier and clothes washer/dryer all at the same time.

If you are on petrol then not so much of a concern.

Awesome, thanks, that's what I thought. So about 4 kW is probably optimum for us, then? (although obvs I'll double-check that!) We're Diesel.

Also, if we put all small-drain items like lights, phone chargers & stereo on the 12v system, and have a battery charger for that hooked up to the generator, then we only need to run it at all when we're using the bigger stuff, right?
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Old 01-02-2015, 11:18   #20
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I live aboard without shore power. Assuming you have no air conditioning, you can run off batteries and an inverter and charge once or twice a day with a diesel generator, as I do. You will want:

Nominal 3kW inverter or more with built in charger and power boost

At least 400a/h of battery capacity @24v (double for 12v)

The smallest heavy duty, low speed, 3-cylinder diesel get set you can find (like the Northern Lights 4.5kW).

I have a Kohler 6.5kW which has been very good, but the size is overkill as battery charger can only take about 2.5kW max. Diesel generators like to be loaded 50% - 75%.

I have lots of electrical gear on board including washer/dryer, kettle, microwave, Nespresso machine, power tools, etc etc. i charge a couple times a day for a couple of hours. The 4.5 kW Northern Lights would work fine for me.
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Old 01-02-2015, 11:22   #21
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? . . Installing a 3KW generator when you need 5KW will leave you as frustrated as over powering your boat needlessly.
Not if you have an inverter with power boost . In which case you size the inverter for max transitory loads and the genset for somewhat less. It s very bad to size the genset for max short-term loads, as this will leave it under-loaded most of the time, inefficient and bad for its health.
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Old 01-02-2015, 11:35   #22
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Re: Best generator for day-in/day-out use?

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I live aboard without shore power. Assuming you have no air conditioning, you can run off batteries and an inverter and charge once or twice a day with a diesel generator, as I do. You will want:

Nominal 3kW inverter or more with built in charger and power boost

At least 400a/h of battery capacity @24v (double for 12v)

The smallest heavy duty, low speed, 3-cylinder diesel get set you can find (like the Northern Lights 4.5kW).

I have a Kohler 6.5kW which has been very good, but the size is overkill as battery charger can only take about 2.5kW max. Diesel generators like to be loaded 50% - 75%.

I have lots of electrical gear on board including washer/dryer, kettle, microwave, Nespresso machine, power tools, etc etc. i charge a couple times a day for a couple of hours. The 4.5 kW Northern Lights would work fine for me.

Excellent, I think I'm set to start the hunt, thank you so much! Final question (I think!): Roughly how long does it take you to charge your batteries each day? Your purposes sound a lot like ours
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Old 01-02-2015, 13:32   #23
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Re: Best generator for day-in/day-out use?

It's a narrow boat so I think we can assume he won't be leaving Europe with it.

If you don't use air conditioning the 4-5kw genset should be plenty. As mentioned an inverter with power boost type feature will be a very good asset. I also agree that a real battery bank is a requirement. I would try to put a big enough battery bank and enough solar panels to power your refrigeration and other basic needs like an anchor light if required at your anchorage. That way you can leave the boat for a few days without needing to have an auto start capability on your genset.
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Old 01-02-2015, 13:48   #24
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Re: Best generator for day-in/day-out use?

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It's a narrow boat so I think we can assume he won't be leaving Europe with it.

If you don't use air conditioning the 4-5kw genset should be plenty. As mentioned an inverter with power boost type feature will be a very good asset. I also agree that a real battery bank is a requirement. I would try to put a big enough battery bank and enough solar panels to power your refrigeration and other basic needs like an anchor light if required at your anchorage. That way you can leave the boat for a few days without needing to have an auto start capability on your genset.

Thanks! Suggestion for a good amount of battery capacity?
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Old 01-02-2015, 13:55   #25
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Re: Best generator for day-in/day-out use?

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Originally Posted by melissiti View Post
Excellent, I think I'm set to start the hunt, thank you so much! Final question (I think!): Roughly how long does it take you to charge your batteries each day? Your purposes sound a lot like ours
It depends. More in the winter with the heat running 24/7 -- it's diesel fired (Eberspacher hydronic) but has pumps and fans and so forth so uses a fair amount of electrical power.

Like a lot of cruisers, I tend to run the generator when I have A/C tasks -- often at dinner time when I'm using appliances. It's more efficient to bunch up power intensive tasks and do them when the generator is running, rather than off the inverter.

Lead-acid batteries are inefficient to charge above 80% or 90%, and they wear out much faster if you let them get below 50% or 60%, so I think it's better to charge them relatively often but not waiting for anything like full charge.

So I will typically shut off the generator when the charger goes into absorption mode, or after a relatively short period of absorption mode. From 50% or 60% to that point typically takes two hours (70 amps x 24v charger into 420 amp/hours x 24v of batteries).

For the sake of their health, your batts need a full charge every week or so. That corresponds with my use pattern, as I often times work on board (or travel) during the week, then go sailing during the weekend, and stay someplace where I can plug in and get a good, full charge on the weekends.

Solar power is really great for those top-off charges which generators are inefficient for, so if you have space to mount them, they are very complimentary to diesel charging.
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Old 01-02-2015, 15:24   #26
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Re: Best generator for day-in/day-out use?

I assume you have a refrigerator that is similar to a regular apartment sized unit rather than a purpose built very well insulated boat refer. I have about 800 amps at 12 volts of golf cart batteries (eight 205 amp 6 volts ) with a big box store refrigerator and it is plenty but not excessive. I don't have children on the boat but The Boss watches TV for a few hours every day. We have no heat when anchored but we try to control temp by how far North we are. You really need to spend the time to add up what you use in a day so you can develop a plan rather than just guess. If you don't have a battery monitor you should get one sooner rather than later. It help you figure this out and will be very useful on a daily basis.
MaineSail was impressed with the Balmar Smart gauge and his advice is worth way more than mine.
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Old 01-02-2015, 16:29   #27
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Re: Best generator for day-in/day-out use?

Ooh, yes, a battery monitor sounds well worth having - thanks for the link!
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Old 01-02-2015, 16:35   #28
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Re: Best generator for day-in/day-out use?

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Ooh, yes, a battery monitor sounds well worth having - thanks for the link!
The Balmar Smart Gauge is made in the UK and can be bought here: SmartGauge Electronics - Homepage It's actually the only thing in the world which is cheaper in the UK than the US, due to Balmar's outrageous markup.
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Old 01-02-2015, 18:13   #29
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Re: Best generator for day-in/day-out use?

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It's a narrow boat so I think we can assume he won't be leaving Europe with it.

If you don't use air conditioning the 4-5kw genset should be plenty. As mentioned an inverter with power boost type feature will be a very good asset. I also agree that a real battery bank is a requirement. I would try to put a big enough battery bank and enough solar panels to power your refrigeration and other basic needs like an anchor light if required at your anchorage. That way you can leave the boat for a few days without needing to have an auto start capability on your genset.
Have to agree that a 4-5kw would be adequate if you don't need AC. If in the future you may require to run a SCUBA compressor you would be best going larger.

Fitting an inverter charger with power boost can be a real advantage with a smaller genset.

Quattro - Victron Energy
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Old 02-02-2015, 03:58   #30
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Re: Best generator for day-in/day-out use?

Ok, bear with me here, the first paragraph below is a kind of 'disclaimer', in the second one I get to the point!

I don't, as yet, have any familiarity with mechanics, electronics, or engineering in general... However, God bless the Internet for instructions & contextual information, and trust me when I say this is the kind of subject matter I'm capable of learning thoroughly and quickly. And I've got friendly acquaintances specialising in all kinds of relevant fields who would help in the case of hiccups...

Now the point: how hard would it be to build my own generator using an old but sound tractor engine & a suitably heavy-duty alternator (& all other parts)? 'Cause I can get pretty much anything from local breakers, if anyone can point me in the direction of what I need to know (basically I know nothing), and decent how-to guides, that kind of thing.

Again, all & any advice gratefully received!
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