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New batteries - something smoking! (Alternator?)


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I just replaced my almost entirely dead lead acid batteries with some new ones and during the early stages of charging I'm getting a steady supply of smoke coming from somewhere. I've checked all the connections and the only thing that feels hot or even warm is the domestic 70a alternator, so I can only assume this is where the smoke is coming from (difficult to tell when its being blown about). 

 

The inside of the alternator appears to have a nice coating of oil inside where it looks like its been sprayed by a leak at some point. However the smoke seems to have a very slightly plasticy electrical smell to it so I'm not sure if it's burning the oil. 

 

This smoke and smell only seems to happen when it's bulk charging at a steady 55 amps or so and has gradually got less as the charging amps have dropped. Because my old batteries only ever hit about 50 amps charging current for a minute or so and then quickly dropped to a steady charge of between 30 or 40 amps I guess the alternator never really got a work out to cause this problem.

 

So having checking everything else I can think of and only finding the alternator becoming hot, is it likely to be the oil on it causing the smoke or could it be something more sinister? Can this be cleaned or is it time to think about replacing it?

 

 

 

 

IMG_20181116_113123.jpg

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Most boat alternators are really only automotive alternators and not totally suitable for running flat out for any length of time. Most will manage but will be running at the top of their temperature range. This is probably the hardest you have worked your alternator.

It might die very soon.

But, once some paint and general crap or whatever has burned off it will probably settle down and manage to cope for a few years. Diode failure is the most likely cause of death, though loss of varnish from the windings is also possible.

 

Make sure the belt isn't slipping as this makes smoke and also puts more heat into the alternator. If you can open up the alternator and clean out the dog hairs etc. (I think I can see a fair bit of crap in those ventilation slots)

Carry a spare alternator.

 

My domestic alternator runs shockingly hot, the last one was good for about three years and eventually died from slip ring wear.

 

There are a few alternator controllers than sense alternator temperature and reduce or shut down charge current as required.

 

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

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First check... is the alternator fan correct for the direction of rotation? It should be pulling the air through the alternator from the back to the front not the other way around. 

 

Secondly... it could be just accumulated crud burning off with the first heat the alternator has had for some time. If so then it will slowly decrease. If it increases then you need to keep an eye on it. 

 

Thirdly... is the fan belt tight? A slipping belt will smoke and smell. 

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Thanks all for the responses.

 

As far as I know the fan is spinning the correct direction.

 

All the heavy wire connections are tight, and can't feel any of them getting warm.

 

The belt is on fairly tight to the 90 degree twisty method. Had to replace it with one an inch shorter as I think the size they had on before was still very slightly loose even at full extension.

 

I will keep an eye on it and make sure it doesn't get any worse, and will get hold of a spare for when the inevitable eventually happens. Would it be better to change for a similar output or should I go for something slightly bigger? My battery bank is 300ah (150ah useable) and the current alternator is 70a on a Beta 35hp.

 

 

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The 90° twist method is only applicable to polyvee belts like this multigroove image. 

 

If it is a normal vee section or cogged belt,  then it is correctly adjusted when there is 15mm of slack on the longest run.

 

If the belt is slack, there will be powdery black deposits around it.

download.jpeg

Edited by cuthound
To add the last sentance
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Are you running at tickover? If so there will be insufficient airflow through the alternator to cool it. The fact you are only getting 50A makes me think so. Get some revs on it.

When I first fitted a Sterling alternator controller on my boat, the alternator poured smoke for hours till all the oily deposits had cleared. It got very hot but It worked fine for about 12 years afterwards.

They do get hot, too hot to touch usually.

Edited by Boater Sam
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2 hours ago, cuthound said:

The 90° twist method is only applicable to polyvee belts like this multigroove image. 

 

If it is a normal vee section or cogged belt,  then it is correctly adjusted when there is 15mm of slack on the longest run.

 

If the belt is slack, there will be powdery black deposits around it.

download.jpeg

Oops. Yeah it's just a normal v belt. The original one which was too big was definitely more than 15mm movement but didn't notice any squealing or powdery deposits. The new belt is much tighter, moves probably not much more than 15mm and no powdery problems there either.

 

2 hours ago, Boater Sam said:

Are you running at tickover? If so there will be insufficient airflow through the alternator to cool it. The fact you are only getting 50A makes me think so. Get some revs on it.

When I first fitted a Sterling alternator controller on my boat, the alternator poured smoke for hours till all the oily deposits had cleared. It got very hot but It worked fine for about 12 years afterwards.

They do get hot, too hot to touch usually.

I never run at tickover for extended periods and especially not when charging. Unfortunately my rev counter doesn't work so not sure of the exact revs but it's usually got some power behind it. I'll try upping it a bit early on in charging to see if that helps.

 

Thanks for the tips.

 

Edited by Rumsky
Wrong peedictive word changed the whole meaning of the sentence
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Your engine, like mine, is a Beta. If your rev. counter doesn't work its worth fiddling around with the multi pin connecters, Mine has 3, the one that just plugs into the back of the rev counter, another one about 18" further down the loom and a bigger one nearer the engine, all nice and snug inside the boat, no chance of rain or anything getting in but the middle one needed a good clean. Rev counter now works again.

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2 hours ago, bizzard said:

To clean it. Remove it. Suspend from the ceiling by the pulley. Dabble around its bottom with industrial spirit, meths or even white spirit with a smallish paint brush. Leave to dry and drain for a while.

All sounds a bit kinky but I'll give it a whirl.

 

2 hours ago, Bee said:

Your engine, like mine, is a Beta. If your rev. counter doesn't work its worth fiddling around with the multi pin connecters, Mine has 3, the one that just plugs into the back of the rev counter, another one about 18" further down the loom and a bigger one nearer the engine, all nice and snug inside the boat, no chance of rain or anything getting in but the middle one needed a good clean. Rev counter now works again.

I have tried faffing about with the connections before but perhaps I missed some. Will work my way down the cables tomorrow and see what's what. The rev counter has never worked since I've had the boat, and last month the hour counter gave up as well. It was still making a very slight 'tick' which suggested it was trying to turn the number dials, but non were turning. I tried giving it a few taps on the glass to try and unstick them but still stuck.

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