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Why don't people have boats with diesel engines AND diesel generators on board.


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I appreciate that I might be missing something blindingly obvious here, but please humour me and let me know what is wrong with my thinking here: 

Imagine for a moment that it's not possible to fit electric motors to a narrowboat, this is about diesel only propulsion. 

I'd like a boat that is gas-less and with plenty of stored power on board i.e. lots of lithium batteries - to run all the electrical appliances. Of course, I can fill the roof with good quality solar panels, which will help keep the batteries charged, perhaps fully in summer, but definitely less so in winter. It seems like a typical diesel engine would be less than ideal for charging duties at other times, or would need running for very long periods to get the job done. 

 

So why not have a in-built generator (like ones used in serial hybrid boats) which is used purely for charging batteries and maybe heating hot water. 

 

So, for propulsion a normal diesel engine (which will do a bit of charging and hearting of hot water) and a generator for doing most of the charging, but much more efficiently. 

 

What are the potential problems, pitfalls or issues with this kind of set-up?  i.e. why is this not a common approach? 

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12 minutes ago, missingtheboat said:

What are the potential problems, pitfalls or issues with this kind of set-up?  i.e. why is this not a common approach? 

 

 

It IS a common approach. I know several people with ordinary diesel narrowboats and cocooned generators.

 

Cost is the main reason not everyone does it as a decent silent genny and a stack of batteries is £20k in round figures. 

 

 

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2 minutes ago, Momac said:

Many salty water motorboats boats do have a separate generator.

 

And some narrowboats, the owners of some are on here. If you want high electrical loads, it is the way to go, especially for winter. One thing to consider is that space tends to be at a premium on narrowboats and the generator has to be fitted in somehow.

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26 minutes ago, missingtheboat said:

why is this not a common approach? 

 

It is not uncommon - the limiting factor for many is the cost of ~£10,000 for the generator and installation.

 

 

Edit to add :

Certainly a lot more common on Coastal / Lumpy water boats where you may anchor up for days / weeks on end.

On the canals, you can 'plug in' at a number of mooring spots or, you can easily pop into a marina for a top up. You get a lot of nights in a marina for £10,000

Edited by Alan de Enfield
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Ah, ok. I guess a common response might be that if you've invested in a generator and a big bank of batteries, you may as well go ahead and add an electric motor too, for some silent cruising - especially for a new build, but it seems like there is less discussion about this kind of set-up, which would seem to have some merit as an alternative to a hybrid electric system. Other than their being two engines to service, noise and less green credentials, are there any other drawbacks when compared to a hybrid system? 

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6 minutes ago, missingtheboat said:

Ah, ok. I guess a common response might be that if you've invested in a generator and a big bank of batteries, you may as well go ahead and add an electric motor too, for some silent cruising - especially for a new build, but it seems like there is less discussion about this kind of set-up, which would seem to have some merit as an alternative to a hybrid electric system. Other than their being two engines to service, noise and less green credentials, are there any other drawbacks when compared to a hybrid system? 

 

But what you describe is a hybrid system. A non-hybrid system would only use solar or land based power for charging. As soon as you add a generator, it becomes hybrid.

Edited by Tony Brooks
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8 minutes ago, MtB said:

One tends to find them on tug-style narrowboats, with the genny under the tug deck.

 

 

That is how a couple of boats I know of are configured.  Genny under the tug deck where the gas locker would be if they had gas.

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Posted (edited)
4 minutes ago, Tony Brooks said:

But what you describe is a hybrid system. A non-hybrid system would only use solar or land based power for charging. As soon as you add a generator, it becomes hybrid.

I appreciate I might not have the correct terminology - it's confusing. What I mean is diesel propulsion, diesel powered charging of batteries, which are used purely for powering the domestic stuff. 

 

I mean, really then, if this were a new boat, we could simply substitute the diesel engine that is driving the boat for an electric motor and the costs would be fairly similar? We'd need to charge the batteries more often of course, but we'd use less diesel overall presumably. 

I'm really trying to understand the differences (other than quiet cruising and less emissions) between this set-up and a serial hybrid with an electric motor. 

Edited by missingtheboat
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The usual arrangement (except perhaps on very large boats) is to use  the propulsion engine for battery charging and water heating .

Switch to the generator when moored  and even then only when required .

 

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1 minute ago, Momac said:

Switch to the generator when moored  and even then only when required

Which I expect is much more efficient than using the (propulsion) engine and helps preserve the condition of the propulsion engine too. Interesting. 

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4 minutes ago, missingtheboat said:

Which I expect is much more efficient than using the (propulsion) engine and helps preserve the condition of the propulsion engine too. Interesting. 

It does certainly help preserve the propulsion engine. 

On a salty water boat running a large diesel engine just to charge batteries is not at all good for the engine.

But also the generator should create far less noise compared to the propulsion engine . Good marine generators are barely addible off the boat with most of the sound being some splashing from the raw water cooling.

 

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hmm, okay - I think that's all a bit clearer in my head now. On a new build at least, once you know you need a decent amount of battery power, you know you'll also need a decent sized generator (for some of the year at least) and so adding an electric motor perhaps makes more sense than adding a diesel engine for propulsion. 

I can see that on an old boat that already has diesel propulsion, it might make more sense to add the bigger batter bank and a generator, rather than replacing the engine. 

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51 minutes ago, Tony Brooks said:

 

But what you describe is a hybrid system. A non-hybrid system would only use solar or land based power for charging. As soon as you add a generator, it becomes hybrid.

If the generator is only for domestic, and there is no propulsion motor, then a generator does not make it hybrid.

 

Basically, you have called every deep sea ship a hybrid. 

Or have I misunderstood?

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Just now, JungleJames said:

If the generator is only for domestic, and there is no propulsion motor, then a generator does not make it hybrid.

that was my understanding too, but happy to be corrected. 

 

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1 hour ago, missingtheboat said:

What are the potential problems, pitfalls or issues with this kind of set-up?  i.e. why is this not a common approach? 

 

It's not common because proper marine diesel generators are quite expensive. You're talking a minimum of £5K before it's installed and installation is at least another grand. Apart from that the only pitfalls or problems I can think of are potentially a lack of space in a some NB engine rooms.

 

If you do decide on a diesel generator then look at 1500rpm units rather than 3000rpm.

 

https://www.northern-lights.com/

 

Edited by blackrose
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1 hour ago, missingtheboat said:

Ah, ok. I guess a common response might be that if you've invested in a generator and a big bank of batteries, you may as well go ahead and add an electric motor too, for some silent cruising - especially for a new build, but it seems like there is less discussion about this kind of set-up, which would seem to have some merit as an alternative to a hybrid electric system. Other than their being two engines to service, noise and less green credentials, are there any other drawbacks when compared to a hybrid system? 

 

3 minutes ago, JungleJames said:

If the generator is only for domestic, and there is no propulsion motor, then a generator does not make it hybrid.

 

Basically, you have called every deep sea ship a hybrid. 

Or have I misunderstood?

 

Yes, you have if you read the context. The OP said that once you have a large battery bank and generator you may as well fit an electric motor rather than a diesel engine, so no diesel propulsion engine. That makes it a self charging hybrid in car terms.

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4 minutes ago, Tony Brooks said:

 

 

Yes, you have if you read the context. The OP said that once you have a large battery bank and generator you may as well fit an electric motor rather than a diesel engine, so no diesel propulsion engine. That makes it a self charging hybrid in car terms.

Ah right. No, I think he moved on from hybrids back to domestic gennies, hence my comment.

Admittedly not the clearest post

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Just now, JungleJames said:

Ah right. No, I think he moved on from hybrids back to domestic gennies, hence my comment.

Admittedly not the clearest post

 

Not the clearest thread, either, but I may have got his intention wrong. I THINK he did go back to diesel propulsion, then talked about using an electric motor and doing away with the diesel.

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I was trying to ease my confusion, not cause any for others so sorry about that! Thanks everyone for the input, and your patience. You're right, it wasn't clear - too many thoughts swirling around my noggin and not enough time spent trying to clarify them. 

We're in the early stages of buying a new boat. We initially thought that we would go down the serial hybrid route (i.e a big battery bank, electric motor for propulsion and a generator that charges the batteries). After talking to a few people, hearing a few things that were a bit off-putting, we thought that we might be fine with a traditional diesel boat. THEN, we learned that if we had a lot of batteries on a standard diesel propelled boat, we'd potentially have problems charging them unless we had a generator (we'll probably cruise for maybe 10 hours a week in total, maybe a less sometimes), so THEN we came back around to 'if we've got loads of batteries and a serious generator, then doesn't it make sense to have the motor (rather than a diesel engine) for propulsion? - I'm assuming that there is not a night and day difference between the up-front cost of a diesel engine or an electric motor for propulsion. 

In my mind, there are pros to having an electric motor for propulsion when compared to a diesel engine: 

Less noise when cruising. 

Less emissions when underway. 

Less maintenance. 
Less spent on diesel. 


...and cons too: 

More complexity (mainly in relation to getting everything matched up properly, which is the stuff I've heard people having negative experiences with)

More regular charging of the batteries required. 

 

As I said, I do feel a bit clearer now, although still have plenty to consider. 

 

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5 minutes ago, missingtheboat said:

I was trying to ease my confusion, not cause any for others so sorry about that! Thanks everyone for the input, and your patience. You're right, it wasn't clear - too many thoughts swirling around my noggin and not enough time spent trying to clarify them. 

We're in the early stages of buying a new boat. We initially thought that we would go down the serial hybrid route (i.e a big battery bank, electric motor for propulsion and a generator that charges the batteries). After talking to a few people, hearing a few things that were a bit off-putting, we thought that we might be fine with a traditional diesel boat. THEN, we learned that if we had a lot of batteries on a standard diesel propelled boat, we'd potentially have problems charging them unless we had a generator (we'll probably cruise for maybe 10 hours a week in total, maybe a less sometimes), so THEN we came back around to 'if we've got loads of batteries and a serious generator, then doesn't it make sense to have the motor (rather than a diesel engine) for propulsion? - I'm assuming that there is not a night and day difference between the up-front cost of a diesel engine or an electric motor for propulsion. 

In my mind, there are pros to having an electric motor for propulsion when compared to a diesel engine: 

Less noise when cruising. 

Less emissions when underway. 

Less maintenance. 
Less spent on diesel. 


...and cons too: 

More complexity (mainly in relation to getting everything matched up properly, which is the stuff I've heard people having negative experiences with)

More regular charging of the batteries required. 

 

As I said, I do feel a bit clearer now, although still have plenty to consider. 

 

KISS everytime.

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2 minutes ago, mrsmelly said:

KISS everytime.

I tend to agree, unless you are 100% capable and willing to undertake all your own servicing and repairs. I suspect it is hard enough to find someone reliable to sort out a lithium charging problem on a diesel boat, if you then add the electric propulsion and control system I suspect that at the resent state of play you would have to rely upon the builder. Give it 10 years and I am sure things will be different.

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And note that diesel powered boats generally have 12V (occasionally 24V) electrics, but electric powered boats are more efficient at higher voltage, typically 48V, as anything above 50V involves higher safety requirements.

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