Alternator size Beta 43. Standard 65amp or uprated 175amp? Recommendations please.

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joyfull

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Looking to reengine with Beta 43hp on 40 foot Jeanneau. The existing 50hp Perkins has an uprated 160amp Lecce Neville alternator fitted. Services on the boat include all the usual plus electric windlass, diesel heating, water heater etc. There are three 110ah agm service batteries and a 110ah lead acid starter battery.

The Beta 43 has 65amp standard or uprated 175amp. Would you recommend staying with the 65, fitting the 160 from the Perkins or going for the Beta 175?
 
joyfull said:
Looking to reengine with Beta 43hp on 40 foot Jeanneau. The existing 50hp Perkins has an uprated 160amp Lecce Neville alternator fitted. Services on the boat include all the usual plus electric windlass, diesel heating, water heater etc. There are three 110ah agm service batteries and a 110ah lead acid starter battery.

The Beta 43 has 65amp standard or uprated 175amp. Would you recommend staying with the 65, fitting the 160 from the Perkins or going for the Beta 175?
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If fitting a new engine I would specify the Beta option so it comes ready fitted and therefore guaranteed. Higher output alternators often need upgraded drive (often twin belts or multivee) so better to use the beta system.

www.solocoastalsailing.co.uk
 
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We've got a similar boat/engine (as you know!) with the 65A alternator for 440Ah (but that's with 300W solar). So I'd agree with pvb = maybe! (but by no means a must)

I think you can also fit a second alternator relatively easily (either from factory or later - with a modification to the crank pulley), so that is also something to consider and gives the advantage of a dedicated leisure alternator and some built-in redundancy.
 
pvb said:
With only 330Ah of service batteries, you really don't need a 175A alternator! The 65A would be fine. If, however, you plan to fit more batteries in future a bigger alternator might be worthwhile.
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Very true.
 
The uprated alt might be higher voltage.
It might also make a bigger contribution to powering the windlass.
Ideally you should look at the specs for both alternators.
It's quite likely the standard item is optimal for a digger engine running a high daily duty cycle and not having its battery used for 'house' purposes while the engine isn't running. Because that is what most standard Kubota engines are meant for.
If you expect to only motor for a short period each day, then getting a lot of charge into the batteries quickly and topping up with solar can be a good strategy.

One might also consider that in the lifetime of the engine, lithium house batteries might become mainstream.
 
TernVI said:
One might also consider that in the lifetime of the engine, lithium house batteries might become mainstream.
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Probably looking at replacing the batteries in two or three years. I guess lithium will be the way then (certainly makes handling my golf cart much easier!)

Would lithium batteries be happier with a higher rated alternator or would they charge ok with the standard Beta 70amp (not 65 as I thought)?
 
joyfull said:
Probably looking at replacing the batteries in two or three years. I guess lithium will be the way then (certainly makes handling my golf cart much easier!)

Would lithium batteries be happier with a higher rated alternator or would they charge ok with the standard Beta 70amp (not 65 as I thought)?
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As pvb said - the batteries will draw what they need (so they’ll charge fine, just take longer on the lower-rated alternator, especially if not topped up by any solar etc.)
 
joyfull said:
Would lithium batteries be happier with a higher rated alternator or would they charge ok with the standard Beta 70amp (not 65 as I thought)?
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A typical drop-in lithium ion battery with 12v and 100Ah can be charged at up to 50A, so if you had a few of those you could soak up the output of a bigger alternator.
 
pvb said:
With only 330Ah of service batteries, you really don't need a 175A alternator! The 65A would be fine. If, however, you plan to fit more batteries in future a bigger alternator might be worthwhile.
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Beta say they have a 120amp mid range option with flat poly belt that is a fair bit less expensive than the 175 that might be sensible option as I am looking to fit some solar when I have found a suitable area for the panel.
 
joyfull said:
Beta say they have a 120amp mid range option with flat poly belt that is a fair bit less expensive than the 175 that might be sensible option as I am looking to fit some solar when I have found a suitable area for the panel.
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It could be, but you're still unlikely to see much more than 50A or so charging into 330Ah of lead-acid batteries. If you add more batteries, a 120A alternator could be an advantage.
 
pvb said:
The batteries decide how much charge they can accept, not the alternator.
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The batteries are not sentient beings. They don't decide anything.
The current flowing in is dictated by the voltage applied to the terminals.
You can put a great deal of current into a battery if you raise the voltage.
 
TernVI said:
The batteries are not sentient beings. They don't decide anything.
The current flowing in is dictated by the voltage applied to the terminals.
You can put a great deal of current into a battery if you raise the voltage.
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Of course you can, but most battery manufacturers recommend a maximum charging voltage, often 14.4-14.6v. At that voltage, the batteries will only take as much current as they need, regardless of whether or not the boat has a giant alternator.

It's a common fallacy that fitting a bigger alternator will increase the charging current; in most cases it won't.
 
As your considering an engine with less power,I would go with the 65amp plenty for your battery capacity.A bigger alternator doesn't make much difference to the amount of amps going in to the batteries.
 
peteK said:
As your considering an engine with less power,I would go with the 65amp plenty for your battery capacity.A bigger alternator doesn't make much difference to the amount of amps going in to the batteries.
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Remember that, regardless of alternator size, the load on the engine will be proportional to the charging current produced.
 
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