Is a 60 amp alternator enough to charge 345ah domestic bank

carrswood

carrswood

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some advice please for my father in-law.
He has just fitted a new Yanmar 3YM30 (29hp) to his Moody 336 in Greece (found an excellent engineer)

They are currently cruising the med - hence they rarely plugin to shore power.

He has 3 x 115ah domestics & a regular cranking battery (all recently new)
Question is - will the 60amp modern Alternator be sufficient??

He is wondering if some form of Alternator 'booster' should be added?

Having forked out for a new engine he would like to avoid the cost of a bigger alternator if possible.

ps - he does have a great big solar panel on a frame off the transom too
 
carrswood said:
some advice please for my father in-law.
He has just fitted a new Yanmar 3YM30 (29hp) to his Moody 336 in Greece (found an excellent engineer)

They are currently cruising the med - hence they rarely plugin to shore power.

He has 3 x 115ah domestics & a regular cranking battery (all recently new)
Question is - will the 60amp modern Alternator be sufficient??

He is wondering if some form of Alternator 'booster' should be added?

Having forked out for a new engine he would like to avoid the cost of a bigger alternator if possible.

ps - he does have a great big solar panel on a frame off the transom too
Click to expand...

we have
1 x 115 Ah engine
3 x 115 Ah domestics
60 amp alternator ( no smart regulator )
it works ok for me
 
carrswood said:
some advice please for my father in-law.
He has just fitted a new Yanmar 3YM30 (29hp) to his Moody 336 in Greece (found an excellent engineer)

They are currently cruising the med - hence they rarely plugin to shore power.

He has 3 x 115ah domestics & a regular cranking battery (all recently new)
Question is - will the 60amp modern Alternator be sufficient??

He is wondering if some form of Alternator 'booster' should be added?

Having forked out for a new engine he would like to avoid the cost of a bigger alternator if possible.

ps - he does have a great big solar panel on a frame off the transom too
Click to expand...

Well, I look at it like this....Its a sailing boat so every run of the motor is short and so should be maximised from the electricity generation aspect.
At any time of day I would guess that at least 5ah are coming out for fridge and other stuff... Hmmm, maybe make that 6.5 ah.
So we need to put back over 100ah in 24 hours. After 1 day, if its cloudy, we might be down to nearly 50% on our 345a batteries. So when we motor out of the anchorage we want to put back in the maximum possible and also do some additional things like maybe make some water from our 12v watermaker. This means 20a on top of charging the batteries.
So we need 25% of 345a which is around the maximum acceptance = 86a plus the additional 20a for other stuff and a bit of investment in the future, which equals 106a.

You said he rarely plugs into shore power, so I would say no to 60a. You need at least a 90a alternator and 110a would be better.
Now is the time to change it while the engineers are there and all is new.

I forgot to add, that the alternator maybe needs a 14.8v regulator as well

3 weeks in a marina would cost the same amount... do it all now
 
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pvb said:
The alternator will be OK, but it would work better with a booster (Adverc/Sterling), which would help to maximise charge efficiency.
Click to expand...

But do bear in mind that with a lot of recharging the standard alternator belt in combination with the booster may give you problems like eating away belts as well as a very hot alternator, especially in the Med. So you may end up with more problems.

I'd say try how the current setup behaves before taking the next step.
 
aluijten said:
But do bear in mind that with a lot of recharging the standard alternator belt in combination with the booster may give you problems like eating away belts as well as a very hot alternator, especially in the Med. So you may end up with more problems.

I'd say try how the current setup behaves before taking the next step.
Click to expand...

A 60A alternator shouldn't eat belts, even running at full output.
 
fuss said:
You said he rarely plugs into shore power, so I would say no to 60a. You need at least a 90a alternator and 110a would be better.
Click to expand...

Unless they're AGM batteries, which will accept a high charge current, a bigger alternator wouldn't really help on a small domestic bank.
 
It does depend on the controller, and/or how long the engine is run for.
Unless you have something like a Sterling booster, the alternator will rarely reach its rated output, and will not hold it once the battery voltage rises.
Belt wear shouldn't be an issue if the alignment is good.

From a previous post - It's unfair to blame the fridge for a > 6 A/H drain. The usual compressor fitted nowadays takes about 4 amps and certainly doesn't run for 100% of the time if there's any insulation involved.

I think it may be kinder to the batteries to charge them gently rather than fitting a big alternator (£20 from a scapyard) and then turning it full on with a "booster regulator". Check the cost of batteries versus the gizmos!
 
carrswood said:
They are currently cruising the med - hence they rarely plugin to shore power.
Click to expand...

sailing boats in these circumstances rarely receive a full charge and almost never receive an equalisation charge. thus the batteries remain in a constant state of undercharge.
Every opportunity to hit them with as many amps as they will accept must be taken if the OP wants to avoid premature replacement of batteries that have died as a result of sulfation.

110a on a single belt is right on the limit
Put a 110a alternator on it with a double belt and a good 3 stage charge regulator. You will then maximise the amps accepted by the batteries at every engine run....which in a sailing boat mainly at anchor is so important.
 
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carrswood said:
ps - he does have a great big solar panel on a frame off the transom too
Click to expand...


Depending on what you mean by "great big", then that will make a HUGE difference. We have 400AH of battery capacity and a 6A alternator (yes, you read that correctly, SIX Amp), we run fridge, computer, instruments, lights etc etc with no problems at all. Our "great big solar panel on a frame off the transom" does the bulk of the work.
 
60A Alternator

The thing is that the 60 amp alternator charging a very large battery bank will tend to charge even after some time at a decent charge rate. (Say 20+ amps) So having a large battery bank you do not have such a need for charge boosting controller. Yes of course a larger alternator and charge booster would be nice but I think he might find it all works fine. If he monitors battery volts and finds the batteries need more charge more often then yes go for a bigger alternator and charge controller but I would suggest give it a go as solar may weel do enough boosting.
good luck olewill
 
I have 675Ah of house batteries and a 60A alternator. Since fitting a Sterling AtoB booster, the difference is noticeable and the whole setup is perfectly adequate, charging from about 12.2v to float charge in about 2 hours.

You will find that fitting a booster will charge your house batteries much quicker, and will give you a better solution than a bigger alternator.
 
Bobc said:
I have 675Ah of house batteries and a 60A alternator. Since fitting a Sterling AtoB booster, the difference is noticeable and the whole setup is perfectly adequate, charging from about 12.2v to float charge in about 2 hours.

You will find that fitting a booster will charge your house batteries much quicker, and will give you a better solution than a bigger alternator.
Click to expand...

A 60a alternator is not ok for 675ah of house batteries, it would be ok for 200ah of house batteries.

If your sterling AtoB charger takes your batteries from 12.2v to float in about 2 hours then the house bank cannot be 675ah.
 
We have 2 x 135 AHr in one bank and 2 x 185 in another + a dedicated starter battery. This is all charged using a Lucas style 60A alternator with a Sterling Regulator.
When motoring, pretty much the only time I see less than 50A on the dedicated meter is after more than 6Hrs motoring or after being plugged in somewhere.

The boat is kept on a swinging mooring so not normally on charge and we have no solar/wind charging. (I do carry a Honda generator when cruising - just in case).
It's worked without a hitch for 12 years other than the solder joint where the lead is attached to the alternator brush failed after 10 years.
The reason for all the batteries was the old fridge using about 6A when running - since changing the mechanism and reducing the current draw to less than 3, I could probably get rid of one set of batteries but why bother...

Cheers
 
You're welcome to come and take a look if you like.

You are quite right that a 60A alt is not ok for 675Ah, but since fitting the AtoB it is.

I have 6 x 6v 225Ah Trojans in 3 banks. I think 225x3=675?
 
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Yes, in a way you are right, it is ok and its not the end of the world.

I'm just saying that the charge time is not maximised and that the correctly sized alternator for the 675ah battery bank would charge the batteries probably more than twice as fast as your 60a setup currently does. No matter what you stick on the end of it, it will still only put out 60a maximum.

At the end of the day every sailing boat spends some time transferring diesel into electricity as in ... "lets just motor a bit longer to give the batteries a bit more charge"

If the charge acceptance is maximised by having the correct sized alternator for the battery bank then this time of additional motoring is minimised.

On a sailing boat this is important as we all dont like running the motor longer than necessary. If you dont mind running the motor just to charge your batteries then this point is not important and an even smaller alternator would also be ok.
 
fuss said:
At the end of the day every sailing boat spends some time transferring diesel into electricity as in ... "lets just motor a bit longer to give the batteries a bit more charge"
Click to expand...



Not so! That may be true of many, even most, but certainly not all sailing boats.


Since the question is about a boat based in the Med with a "great big solar panel on a frame off the transom", that suggests to me that the posts here which ignore the contribution of solar are of limited value.
 
On our last "proper" passage, we had the fridges and instruments on 24/7, and the nav lights on at night, and we were running the motor for 2 hours in the morning, and a further 2 hours in the evening, which put them onto float each time, which I thought was pretty good overall.

I can't emphasise enough what a difference the AtoB made though. Previous to fitting this it was really hard to get the batteries to fully charge without shore power (even by running them for 4 or 5 hours), hence my comment that an alt on it's own is no good.
 
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