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Single Alternator


Celestine

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Hi, I'm looking at buying a narrow boat that has only one alternator fitted to the engine. I've had three boats in the past, all having had two fitted. Are there any problems that I should be aware of with a one alternator system.

The boat is fitted with a Nanni Kubota 450 engine. My thoughts are just to carry a spare, are spares readily available? 

Many Thanks.

 

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Single alternator installations tend to have poor  / inadequate power output for 'modern' requirements. Usually they're only 'good' for charging the engine starter battery.

Thus - as usual more information is needed to give an helpful reply...

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6 minutes ago, OldGoat said:

Single alternator installations tend to have poor  / inadequate power output for 'modern' requirements. Usually they're only 'good' for charging the engine starter battery.

Thus - as usual more information is needed to give an helpful reply...

I'd take a completely different view.

On many narrow boats that have 2 alternators fitted, all one is ever doing is keeping the starter battery topped up - which in practice is close to zilch.

It is the second one that is actually doing 99.9% of the work providing domestic services.

Only if you have the two paralleled in some way, or can easily switch between one is much gained by having two.

Many boats do perfectly well with one, but if you are worried about having no redundancy if it fails, simply carry a siilar one as an easily substituted replacement.

Edited by alan_fincher
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There are hundreds, likely thousands, of boats chugging about driven by an old BMC engine with a single alternator.

Carrying a spare alternator, ready to go with pulley fitted, and a couple of spare belts, would be an excellent idea.

...........Dave

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12 minutes ago, alan_fincher said:

Single alternator installations tend to have poor  / inadequate power output for 'modern' requirements.

You may want to ensure that the output of the single alternator is enough to put back the power you have used within reasonable number of hours of running the engine and also to see that the charging voltage is right for the batteries that you have.

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I would just like to point out that in the above posts the quote that says

Quote

Single alternator installations tend to have poor  / inadequate power output for 'modern' requirements.

has somehow been credited to me.

Unfortunately I don't think that at all!

 

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1 hour ago, alan_fincher said:

I would just like to point out that in the above posts the quote that says

has somehow been credited to me.

Unfortunately I don't think that at all!

The forum does that occasionally. I think it’s personal. 

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7 minutes ago, philjw said:

I think that it has happened on this occasion by copying text that is within a quote.  The quote is then attributed to the writer of the post that included the text n which had actually been written by an earlier contributor.

Yup, I just tried it and you’re right, it does that. 

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Thanks for the response.

According to the Nanni 4.50 online engine manual (2017), the alternator fitted is 120 amp.  The boat was built in 2005 so not sure if the alternator has the same output as quoted now. The boat is also fitted with solar panels.

Are Nanni spares readily available, only have experience with Beta.

The boat is moored a good distance away from home, so I want to have some info before requesting a viewing.

Thanks

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12 minutes ago, Celestine said:

According to the Nanni 4.50 online engine manual (2017), the alternator fitted is 120 amp.  The boat was built in 2005 so not sure if the alternator has the same output as quoted now. 

You’d have to confirm of course, but if it does indeed have the 120A alternator then that will do you just fine. 

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Yes, perfectly happy with a single 70 amp alternator but then we are a 12V boat with only the fridge making a"high" current demand.

I would say avoid  having a split charge diode UNLESS it is a true zero voltdrop box of electronics. Nowadays I would go for a Voltage Sensitive Relay (VSR), especially if solar is in use or planned because that would allow solar to charge both banks when possible.

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I've managed for 40 yrs with one alternator.  Hardly any energy is taken out of the engine battery. 

As others have noted, worth checking that the charging system is focussed on  domestic battery. So any sensor goes to domestic (e.g. if adverc is installed) and any relay connects engine battery to domestic & alternator,  not other way round

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10 hours ago, Scholar Gypsy said:

any relay connects engine battery to domestic & alternator,  not other way round

I think this could be misinterpreted by someone who doesn’t understand so please allow me to re-word it. 

The single alternator should be wired directly to the domestic bank and any split charge device should then connect the engine battery to that bank. 

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3 minutes ago, WotEver said:

I think this could be misinterpreted by someone who doesn’t understand so please allow me to re-word it. 

The single alternator should be wired directly to the domestic bank and any split charge device should then connect the engine battery to that bank. 

Yes, that's much clearer. Thanks..

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