Self inflicted charging problem

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kalanka

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I commissioned the boat for the new season yesterday. All went smoothly but, when just about to leave the boat, I mistakenly started a warm engine whilst the breaker on the main power circuit was off - no power. A minute or two after starting I noticed no lights were illuminated on my Sterling charge management device and increased revs to c 2000 rpm to see if it was rpm related.

No effect, so immediately shut down with the normal pull lever and then realised my mistake. Re-started with main circuit on and engine ran fine but still no lights on Sterling. Tacho continued to read throughout.

At that point I suspected the Sterling was the problem but now am more inclined to think I may have buggered up the alternator diodes. I would welcome a diagnosis from someone who understands charging.

How do I fix the problem? Am I right to think I have now lost charging? Should have checked when on board but only realised this later......

VP 2003 engine. Engine ran well for a 2 hour outing under power but charging may have been sluggish. Battery bank is 200 Ah and went from 65% charge to 90% in the 2 hours with plotter and auto helm in use. Sterling lights were illuminated.

I vaguely remember some previous issue with the Sterling which required a relay to be "primed" in some way. This may not be relevant to the present case.

Thanks.
 
Boater Sam said:
If wired correctly you should not be able to start the engine with the alternator output not connected to a battery.
Click to expand...

?????

Engines can be started and run without alternator connected.

From memory, the Sterling can be disconnected by disconnecting one wire so I would do that, then run engine and check charging voltage with multi-meter.
 
Starting engine with Alternator OFF ... is not normally a problem as the alternator will not energise ...

But switching an alternator OFF while engine is running will most often blow the alternator diodes.

I suspect OP has a different problem ....
 
kalanka said:
I commissioned the boat for the new season yesterday. All went smoothly but, when just about to leave the boat, I mistakenly started a warm engine whilst the breaker on the main power circuit was off - no power. A minute or two after starting I noticed no lights were illuminated on my Sterling charge management device and increased revs to c 2000 rpm to see if it was rpm related.

No effect, so immediately shut down with the normal pull lever and then realised my mistake. Re-started with main circuit on and engine ran fine but still no lights on Sterling. Tacho continued to read throughout.

At that point I suspected the Sterling was the problem but now am more inclined to think I may have buggered up the alternator diodes. I would welcome a diagnosis from someone who understands charging.

How do I fix the problem? Am I right to think I have now lost charging? Should have checked when on board but only realised this later......

VP 2003 engine. Engine ran well for a 2 hour outing under power but charging may have been sluggish. Battery bank is 200 Ah and went from 65% charge to 90% in the 2 hours with plotter and auto helm in use. Sterling lights were illuminated.

I vaguely remember some previous issue with the Sterling which required a relay to be "primed" in some way. This may not be relevant to the present case.

Thanks.
Click to expand...

No harm will normally be done if the engine is started and run with the alternator disconnected from the battery.

What causes the problem is disconnecting the alternator while the engine is running.
All the electrons dashing along the wire suddenly have nowhere to go, pile up and cause a voltage surge which can blow the diodes in the alternator.

If you were able to start the engine with the alternator isolated it follows that you will be able to isolate the alternator, by opening the main power circuit breaker, while the engine is running. Take care that you, or a well meaning crew member, do not do that.

I would be rethinking the way it is wired
 
Just a bit more on this engine starting / alternator bit.

Many boats like mine still have the old 1 - both - 2 - off power switch. This is fine as long as we remember never to switch OFF or go via OFF to another battery !! The switch is make before break to avoid blowing alternator diodes.

But I cannot start engine if my switch is not on ... so maybe 'Boater Sam' has confused this with alternator not on ??

Note : I am not interested in being told to remove my power switch thank you .. its been perfectly fine for over 40yrs of the boats life and will no doubt carry on for another 40 well past my shuttle point !!
 
Refueler said:
Just a bit more on this engine starting / alternator bit.

Many boats like mine still have the old 1 - both - 2 - off power switch. This is fine as long as we remember never to switch OFF or go via OFF to another battery !! The switch is make before break to avoid blowing alternator diodes.

But I cannot start engine if my switch is not on ... so maybe 'Boater Sam' has confused this with alternator not on ??

Note : I am not interested in being told to remove my power switch thank you .. its been perfectly fine for over 40yrs of the boats life and will no doubt carry on for another 40 well past my shuttle point !!
Click to expand...
My boats the same with the 1,2,both switch .
 
Refueler said:
Many boats like mine still have the old 1 - both - 2 - off power switch. This is fine as long as we remember never to switch OFF or go via OFF to another battery !! The switch is make before break to avoid blowing alternator diodes.
Click to expand...

Many 1,2,both switches have an internal micro switch which is for connecting to the excite circuit to avoid this problem. Ours has one but wasn't connected that way from new and, as I don't have occasional crew to foul things up, I haven't bothered rewiring.
 
Graham376 said:
Many 1,2,both switches have an internal micro switch which is for connecting to the excite circuit to avoid this problem. Ours has one but wasn't connected that way from new and, as I don't have occasional crew to foul things up, I haven't bothered rewiring.
Click to expand...


TBH - I've never heard of that ...

I would be reluctant to have such a wire. Where would the alternator charge go if that was connected if main power switch is off ?

Excite wire does nothing when alternator is working because its effectively at 0v ....
 
Refueler said:
TBH - I've never heard of that ...

I would be reluctant to have such a wire. Where would the alternator charge go if that was connected if main power switch is off ?

Excite wire does nothing when alternator is working because its effectively at 0v ....
Click to expand...

Here is a description and diagram of a Blue Sea battery selector switch with field disconnection

Alternator Field Disconnect - Blue Sea Systems
 
Refueler said:
Ok ... Tks ...

But I note that it specifically says that it only works with separate EXTERNAL rectifier .... not much use on my boat ...
Click to expand...
External regulator , not rectifier .... not common I guess although one of my cars has one.

I imagine you could probably modify the internal wiring to interrupt the connection to one of the brushes ......... ISTR you modifying an alternator with a diode to boost the output as described by Garrod. Much the same sort of thing
 
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