battery bank

[mikevye]

I like to keep up with the latest manufacturers specs on the boat and have just printed out Barrus Shires engine manual. It has an additional three pages from the original supplied with the boat and page 17 deals with the domestic battery bank. Briefly it states that the battery bank should not exceed more than 3 x output of the 110 amp standard fit alternator or the warranty on the alternator will be void. There is a dispensation giving an example of 3.5x110 for hire boats and 4xoutput if it has Barrus approved alternator management system. So in the case of hire boat it gives a written example 3.5x110=385ampere/hourmaximum battery bank size. Experts whats all this about? Having fitted 6x110 amps instead of 2x220 amps am I now in the situation of having to buy a higher output alternator?

[KenK]

I like to keep up with the latest manufacturers specs on the boat and have just printed out Barrus Shires engine manual. It has an additional three pages from the original supplied with the boat and page 17 deals with the domestic battery bank. Briefly it states that the battery bank should not exceed more than 3 x output of the 110 amp standard fit alternator or the warranty on the alternator will be void. There is a dispensation giving an example of 3.5x110 for hire boats and 4xoutput if it has Barrus approved alternator management system. So in the case of hire boat it gives a written example 3.5x110=385ampere/hourmaximum battery bank size. Experts whats all this about? Having fitted 6x110 amps instead of 2x220 amps am I now in the situation of having to buy a higher output alternator?

 

The standard answer in cases like this is to refer to Gibbo's website http://smartgauge.co.uk and read the technical info. He does an excellent explanation of battery versus alternator size.

 

cheers

 

Ken

[mayalld]

The standard answer in cases like this is to refer to Gibbo's website http://smartgauge.co.uk and read the technical info. He does an excellent explanation of battery versus alternator size.

 

cheers

 

Ken

 

Gibbo's site is concerned with how the alternator rating affects the batteries.

 

This seems to be a question of how the batteries affect the alternator, and seems to be based around not having the alternator producing full current for many hours on end.

[KenK]

Gibbo's site is concerned with how the alternator rating affects the batteries.

 

This seems to be a question of how the batteries affect the alternator, and seems to be based around not having the alternator producing full current for many hours on end.

 

I suspect that a fairly large alternator charging a fairly small battery bank will be more detrimental to the life of the batteries rather than the other way around. Three 110 amp batteries is not a lot of available capacity for a modern boat, it would not take long to reduce them below the 50% charge level with only a reasonable level of electrical equipment. My 70 amp alternator has been charging 660 amps of batteries for the last three years doesn't seem to have done it any harm and the batteries are still ok as well.

 

Ken

[Guest User]

I guess the simplest route for a new installation is to opt for the 160A alternator and only have a max of a 480 amphour domestic battery bank.

 

Barrus don't appear to list any "Barrus approved alternator managment systems", so I guess its a question of ringing them up and asking what is acceptable for your 660 amphour bank. I'd still want it in writing if it was likely to affect the validity of a warranty on a new installation

[PaulG]

I like to keep up with the latest manufacturers specs on the boat and have just printed out Barrus Shires engine manual. It has an additional three pages from the original supplied with the boat and page 17 deals with the domestic battery bank. Briefly it states that the battery bank should not exceed more than 3 x output of the 110 amp standard fit alternator or the warranty on the alternator will be void. There is a dispensation giving an example of 3.5x110 for hire boats and 4xoutput if it has Barrus approved alternator management system. So in the case of hire boat it gives a written example 3.5x110=385ampere/hourmaximum battery bank size. Experts whats all this about? Having fitted 6x110 amps instead of 2x220 amps am I now in the situation of having to buy a higher output alternator?

 

I have a small battery bank (220Ah) and an equally small alternator (45 AH), so I've been breaking the Barrus "Rule of thumb" from the outset. Nearly 20 years later, all is well with the alternator. The batteries are not the originals, however.

 

The handbook that was supplied with the boat at the time of purchase is the controlling document in the contract, so in the absence of any instructions to the contrary at the time, you were quite within your rights to fit your 6 x 110 amp batteries. If Barrus have contacted you in the meantime to inform you of a possible problem, then the situation may be slightly different, I'm not sure.

 

However, reading between the lines it seems possible that Barrus have been getting a lot of warranty claims on their alternators, so if reliability is a big issue for you, you might want to upgrade it for your own peace of mind.

 

PS I'm not an expert!

[churchward]

Interesting. My 70amp alternator charging 3 110amp batteries must be impossible then! I must give the alternator a good talking to when I next get to the boat.

 

As many will know I am far from being an expert in this field but I can't within reason see why the size of alternator dictates the size of battery bank. Surely with a smaller alternator it will just take a bit longer to charge.

 

Unless they are worried that the alternators can't stand the heat of being in an enclosed engine bay operating at full tilt for an extended time?

[Gibbo]

Oh dear me!

 

I will be careful of what I say..............

 

For many years one particular engine supplier has had problems with alternators burning out. At a certain boatyard I was involved with it was a running joke.

 

None of the other engine suppliers have this problem.

 

An alternator should be capable of running at full power day in day out without problem. If it can't then it's either a crap alternator or there is insufficient ventilation and the regulator doesn't have temperature sensing to protect the alternator (as they nearly all do).

 

Adding an external controller will not, under any circumstances, help this issue. If anything it will make it worse. You can draw your own conclusions on why they say a big battery bank is ok if you pay for a controller.

 

Gibbo

[churchward]

An alternator should be capable of running at full power day in day out without problem. If it can't then it's either a crap alternator or there is insufficient ventilation and the regulator doesn't have temperature sensing to protect the alternator (as they nearly all do).

 

When putting a rover V8 in a Morris Minor for someone (I know! ) we had problems because the alternator was in a funny place and getting a bit too hot and didn't have enough air flow around it to cool it we rigged up a length of radiator hose (say 1-1.5 inch) with the other end at the front of the car so that when it went along air would be forced up the hose and cool the alternator. It worked a treat. I have also seen it done on boats but instead of air being forced up the pipe it just vents from the back of the alternator to the outside by convection.

 

Simple and cheap if anyone needed a bit of cooling for the alternator.

Edited June 24, 2009 by churchward

[Arnot]

am I now in the situation of having to buy a higher output alternator?

 

It seems to me that if you already have the engine then you might as well give it a go, you have nothing to lose. If you don't have the engine then specifying a larger alternator would have some benefits in terms of faster battery charging.

 

There is really no technical reason why a well built and installed 110A alternator should not charge a 660Ah battery bank, it will just do it a bit more slowly than it could be done. The problem seems to be that when a small alternator is charging a large battery bank, it has to run at or near maximum output for longer. This in turn leads to the alternator getting hotter than is good for its long term reliability. The probem is more pronounced when the engine is run at the minimum speed necessary to achieve a decent charging current.

 

As a rule of thumb, wet your finger and touch the stator after the alternator has been running for ten minutes or so, if it hisses then it's too hot. If the smoke escapes, it was far too hot (but it's too late). When an alternator gets too hot, there are two main types of long term damage it sustains, one is overheating of the insulating varnish that the stator wires are coated in which tends to lead to early failure. The other is that the bearings are cooked and the lubricating grease dries out leading to early failure.

 

Like Gibbo, I really don't see the Barrus comment that larger battery banks can be used if an external controller is used, this would cause even more stress on the alternator. In general terms the losses (heat produced) in an alternator are proportional to the square of the current so even a modest increase in the stator current that an external controller would probably lead to will give rise to quite a pronounced increase in the core temperature. Perhaps this is why Barrus are engine distributors rather than alternator manufacturers...

 

In my experience, things that shorten an alternators life are;

poor cooling due to poor engine space cooling.

running the alternator at moderate speed with the highest possible output for long periods regularly.

a combination of engine oil and/or dog hair accumulated over a period of time (this doesn't smell to good either).

loose fanbelt leading to the slipping pulley getting hot and transferring the heat to the rotor shaft.

 

In my experience, things that lengthen an alternators life are;

charging your battery whilst cruising so that there is often more cooling and less output.

buying a decent alternator in the first place such as a Leece Neville.

making sure that the fanbelt is not slipping and ideally having a polyvee belt.

making sure that there is a system for keeping the air in the engine space as cool and clean as possible.

making sure that the alternator is well secured to a strong mounting so it doesn't get shaken to bits.

 

I am sure that there is lots left out of this but I hope what is here helps.

 

Regards

 

Arnot

[Biggles]

My 70 amp alternator has been charging 660 amps of batteries for the last three years doesn't seem to have done it any harm and the batteries are still ok as well.

 

Ken

 

 

That's good to know.

[mayalld]

Oh dear me!

 

I will be careful of what I say..............

 

For many years one particular engine supplier has had problems with alternators burning out. At a certain boatyard I was involved with it was a running joke.

 

None of the other engine suppliers have this problem.

 

An alternator should be capable of running at full power day in day out without problem. If it can't then it's either a crap alternator or there is insufficient ventilation and the regulator doesn't have temperature sensing to protect the alternator (as they nearly all do).

 

Adding an external controller will not, under any circumstances, help this issue. If anything it will make it worse. You can draw your own conclusions on why they say a big battery bank is ok if you pay for a controller.

 

Gibbo

 

I note that what is called for is not any old controller, but an approved controller.

 

Perhaps the approved controller is specially designed to give the alternator a rest for 10 minutes after every half hour of running....

[Sir Nibble]

Hmmn. Well now, this is interesting. I don't believe Barrus are reasonable at all here as far as the alternator goes. As Gibbo says, the machine should be good for it's full out put all day, remember, it was probably never meant to charge batteries being intended to take the load of a fully equipped modern car in winter at night in the rain, ALL night. They must have their reasons tho' and I would suggest a poor installation, either pullied up wrong with problems arising from,

running the alternator at moderate speed with the highest possible output for long periods regularly.

As Arnot says, or being mounted in such a way that engine components impede the airflow, such as some Rovers where a poor innocent little A127 is mounted with the exhaust manifold about 100mm behind it.

From the point of viem of some engine suppliers alternators are just bought in bolt ons and they are no more interested in it's requirement than the paint! Perhaps some lack of sympathy for the alternators needs has come home to roost here.

[mikevye]

As usual the forum comes up trumps the concensus being should be OK with Barrus introducing an opt out clause to cover warranty claims! 330 amp is not a lot of stored energy for modern living purposes and I would think that few boats have this limited amount especially if the engine start battery is being charged by the same alternator. How many people in practise flatten the batteries with the need to have the alternator on full chat for hours attempting to recharge the battery bank? Or are they saying that when the boat is in use the draw on the batteries is such that the alternator is continually playing catch up and never reduces its output below maximum!

[nb Innisfree]

When I designed our NB I assumed it would be unrealistic to expect the engine aternator to cope with domestic demands and therefore fitted a larger more robust one dedicated to the domestics. If Barrus apply their restriction on the engine alternator only and not on a second dedicated domestic, if fitted, then I think they are being reasonable.

[churchward]

As usual the forum comes up trumps the concensus being should be OK with Barrus introducing an opt out clause to cover warranty claims! 330 amp is not a lot of stored energy for modern living purposes and I would think that few boats have this limited amount especially if the engine start battery is being charged by the same alternator. How many people in practise flatten the batteries with the need to have the alternator on full chat for hours attempting to recharge the battery bank? Or are they saying that when the boat is in use the draw on the batteries is such that the alternator is continually playing catch up and never reduces its output below maximum!

I think for a liveaboard your are correct but for a boat used as a holiday/intermittent use boat then a bank of x3 110 amp/hour is not unusual. We indeed have that as our bank and charging daily from a 70amp alternator we get to about 75% charge in the mornings.

[Gibbo]

I note that what is called for is not any old controller, but an approved controller.

 

Perhaps the approved controller is specially designed to give the alternator a rest for 10 minutes after every half hour of running....

 

But that's my point.

 

Even if the external controller does try to do that, the internal reg (which is always left connected) will simply take over when the external one tries to shut down. So fitting an external controller can never improve things.

 

I find it interesting that only this one engine supplier has this problem. None of the others do.

 

Further, the entire engine is supplied as a package (with the alternators already fitted) as a "boat engine". They market them at narrowboats. I really think there is an argument against it being "fit for purpose".

 

Gibbo

[mikevye]

But that's my point.

 

Even if the external controller does try to do that, the internal reg (which is always left connected) will simply take over when the external one tries to shut down. So fitting an external controller can never improve things.

 

I find it interesting that only this one engine supplier has this problem. None of the others do.

 

Further, the entire engine is supplied as a package (with the alternators already fitted) as a "boat engine". They market them at narrowboats. I really think there is an argument against it being "fit for purpose".

 

Gibbo

 

Barrus domestic alternator is supplied with a fly lead already fitted for the purpose of hooking up to an external regulator with no attachment on it to explain its purpose and right next to it is a male connector that to the uninformed looks as if its come off, could this be the reason their alternators fail! When connected it bypasses the internal regulator and puts full output to the batteries and yes I was the numpty that connected the two up albeit in mitigating circumstances so I speak from experience. Gibbo is right though the Barrus engine is supplied complete and it ain't cheap so if the alternator keeps failing it should be a warranty problem not a battery bank size problem!

[Tony Brooks]

But that's my point.

 

Even if the external controller does try to do that, the internal reg (which is always left connected) will simply take over when the external one tries to shut down. So fitting an external controller can never improve things.

 

I find it interesting that only this one engine supplier has this problem. None of the others do.

 

Further, the entire engine is supplied as a package (with the alternators already fitted) as a "boat engine". They market them at narrowboats. I really think there is an argument against it being "fit for purpose".

 

Gibbo

 

 

And which mariniser decided that it was acceptable engineering practise to run a single V belt over four pulleys with no jockey wheel(s) to increase the wrap? I note they no longer do this.