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Burning out alternators


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Since acquiring latest boat last summer,I am having serious alternator problems. I have now had the unit re-conditioned three times and it has just stopped working again. The auto electrician (the latest one) reckons he can tell if the fault is on the boat rather than the alternator itself if I let him have a look. Do I trust him? Not sure. Batteries have all been replaced, cabling and wiring seems ok. It is a Betamarine engine with what appears to be the original alternator labelled 55amps. Any ideas anyone?

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One of ours kept melting the solder connections of the diodes. I put a replacement in, same thing happened.Turned out to be a knackered battery.

Hopefully not a problem for the OP if the batteries are new and in good condition.

Edited by rusty69
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5 minutes ago, rusty69 said:

One of ours kept melting the solder connections of the diodes. I put a replacement in, same thing happened.Turned out to be a knackered battery.

Hopefully not a problem for the OP if the batteries are new and in good condition.

They say the batteries have been replaced so you would hope that isn't the fault!

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5 minutes ago, rusty69 said:

One of ours kept melting the solder connections of the diodes. I put a replacement in, same thing happened.Turned out to be a knackered battery.

Hopefully not a problem for the OP if the batteries are new and in good condition.

Also wise to have a decent monitoring kit to see if theres owt wrong when charging.

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It could be a fault on the main input-output cable on the alternator, probably red. the thick one.  It might be worth doubling it up or replacing it. It should go from the alternator to the + pos post on either the start battery or the babin battery.   The -neg side should be ok if your engine starts up ok.  Many of these cheapo alternator reconditioners just have a big heap of old units and bits and recondition allternators with old S/H bits from the heap. I've been in many such places in the past and you wouldn't believe what its like with whats going on with the big heap out the back. 

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Very difficult to give a reliable opinion without knowing precisely what went wrong inside the alternator each time. Bizzard is quite correct in saying that not all reconditions are what they claim to be. If you can find numbers on the alternator or even a picture I can hazard a guess. The most likely cause of repeated failure is under cooling due to insufficient speed or poor ventilation.

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If it's 55a on a Beta engine, unless it's a small one, it's quite possibly the alternator for the starter battery, in which case replacing the "batteries" (which suggests the domestic bank) won't have affected the issue.  Just a thought...

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To be fair, some parts are fine second hand so long as they have been selected, tested and refurbed by a bloke who knows what he's doing. If your alternator needs a brush set would you really want to pay for regulator, rectifier, rotor and stator to replace servicable parts because you have been using them? I replace brushes and bearings as a matter of course and anything else that fails test.

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2 hours ago, Sir Nibble said:

The most likely cause of repeated failure is under cooling due to insufficient speed or poor ventilation.

 

A future problem for when lithium batteries ever become popular, which can just keep on sucking up all the juice an alternator can deliver. 

 Car alternators are not designed to run at their rated output continuously, they generally overheat eventually. A battery with a shorted cell can probably do this to an alternator too. Do any of your batts get hot during charging?

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Had the same problem with my previous boat. In my case I had a 55amp alternator, blocking diode and Stirling Alternator Controller. After tips from this forum I ditched the Sterling for an Adverc. Apparently Stirling's put a heavy load on the alternator whereas Adverc are kinder to the system. I know Sterling's work well for some folks but for me  shifting away from Sterling worked

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17 hours ago, plainsman said:

Had the same problem with my previous boat. In my case I had a 55amp alternator, blocking diode and Stirling Alternator Controller. After tips from this forum I ditched the Sterling for an Adverc. Apparently Stirling's put a heavy load on the alternator whereas Adverc are kinder to the system. I know Sterling's work well for some folks but for me  shifting away from Sterling worked

Theoretically it should make no difference but in practice I found some alternators really didn't like it. Hitachi machines for instance would desolder the rectifier. Not the stator to rectifier connections put there by yours truly but the individual diode connections put there by the manufacturer.

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I ha don't an alternator refurb at a place near Emsworth, Hampshire. Tiny little unit on a small industrial site. First class. The alternator lasted another eight plus years. Suppose depends on what was wrong with it.

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Beta's engine come supplied with a very cheap and nasty alternator as standard. Fine for topping up the starter battery - but for nothing else. It's not generally a problem as most ? purchasers fit a second higher powered alternator  (I think the 'standard' NB package has two anyway).

Rather than fiddling around with the inadequate alternator - see if you can fit a different type within the confines of whatever bracketry you have.

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Actually, I have just thought of a good example of using second hand parts. Last week a valeo 60A unit arrived on my bench. The first part of my test /inspection routine is to test the complete unit and it was making a maximum around 20A. Having stripped it visual inspection showed heat blistering of the insulation in every third slot of the stator winding, clearly one phase. A replacement stator would be available only from valeo, take ages to obtain and be expensive. However, you learn a thing or two in 40 years so I removed a stator from a 70A A127 off the scrap pile, cleaned and revarnished it and built the unit with that in. Yes it fits exactly, the customer gets an uprated output which experience tells me the rectifier will be happy with and everyone's a winner. The rest of the unit got the usual marine coatings, plated fastenings, bearings and regulator and went out literally better than new.

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I have had a succession of  updated 127 clones over the last few years. All are Indian/ polish copies. With care they last 2 years and we only have two batteries, but boat a lot. I have taken to carrying a spare at all times. I have also learned how to strip and rebuild them and invariably it's the diode pack.. Our boat is not very power hungry, but has an advec fitted, and I have learned to let the alternator charge just the batteries for the first hour every day , if I start up and put all the energy using equipment on too early ( washing machine laptop charger hot water heater) the advec holds the charge rate at full output and melts the alternator. Standard car alternators are designed to charge a start battery for a few minutes only and then supply ancillaries not run at 70a for hours. Also cooling for an alternator is a major factor in their life, in a box under a deck with no wind is going to kill them.

if I could find a real lucas I would but probably made in poland

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10 hours ago, roland elsdon said:

I have had a succession of  updated 127 clones over the last few years. All are Indian/ polish copies. With care they last 2 years and we only have two batteries, but boat a lot. I have taken to carrying a spare at all times. I have also learned how to strip and rebuild them and invariably it's the diode pack.. Our boat is not very power hungry, but has an advec fitted, and I have learned to let the alternator charge just the batteries for the first hour every day , if I start up and put all the energy using equipment on too early ( washing machine laptop charger hot water heater) the advec holds the charge rate at full output and melts the alternator. Standard car alternators are designed to charge a start battery for a few minutes only and then supply ancillaries not run at 70a for hours. Also cooling for an alternator is a major factor in their life, in a box under a deck with no wind is going to kill them.

if I could find a real lucas I would but probably made in poland

 

And this is a lesson Lithium battery early adoptors are going to learn in droves. Lithiums can hoover up every scrap of current an alternator can deliver for hours on end, which is going to result in a lot of new work for Snibs!

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7 hours ago, Mike the Boilerman said:

 

And this is a lesson Lithium battery early adoptors are going to learn in droves. Lithiums can hoover up every scrap of current an alternator can deliver for hours on end, which is going to result in a lot of new work for Snibs!

There is a possibility that a range of alternators will be coming out specifically for boats designed by yours truly and this is something that will have to be considered.

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On 26/03/2018 at 18:49, Sir Nibble said:

There is a possibility that a range of alternators will be coming out specifically for boats designed by yours truly and this is something that will have to be considered.

Sounds interesting. Keep us updated!

As an aside, what's the difference between a 70a and 110a alternator supplying a continuous load of 1200w vacuum and 450w sander (via inverter); say about 150a, for a period of 3hrs or so, and the same setup charging lithium batteries for an hour or 2? I keep getting told the later won't work, even with external controller with alternator temp sensor. 

Haven't got lithium batteries yet, but seriously considering them later this year. 

Tom

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A 70A alternator will give a max of about 900W where as a 110A alternator will be able to output a max of about 1400W.  So if total load is 1200W then the big alternator will cope whereas the little alternator will not and part of the load will be supplied by the batteries.  If demand is less than the alternator utput all is well, if more then the batteries will be discharging.........

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16 hours ago, Tom and Bex said:

what's the difference between a 70a and 110a alternator supplying a continuous load of 1200w vacuum and 450w sander (via inverter); say about 150a, for a period of 3hrs or so, and the same setup charging lithium batteries for an hour or 2?

Why has the lithium charging time in the above scenario dropped to 1-2 hours? 150A used for 3 hours is 450Ah whereaver it comes from. If you regularly use 450Ah per day then that’s 3 hours flat out running from your alternators to charge lithiums every day, 365 days of the year. I doubt you’d use a sander and vacuum every day, would you?

Put another way, occasionally running an alternator flat out is unlikely to significantly shorten its life. Running an alternator flat out for several hours every day WILL significantly shorten its life. 

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The example with sander and vacuum was just to demonstrate the alternators were quite happy producing 150a for 3hrs, so can't see why they won't charge lithium batteries for about an hour a day? Our electric usage is quite low, 70-80ah a day max so easily replaced in 1 hrs charging or less, yet some people insist our standard alternators will overheat and burn out if used for charging lithium batts. Just can't understand the difference.

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