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Discussion Starter #1
This has been an issue since I bought the boat and three yards have expensively failed to fix it. I have a Yanmar JH series engine with a large AMP alternator regulated by a Balmar Maxcharge MC-612 reg.

At tickover and during early running all is well. The system charges and the tachometer works normally. After a while the tachometer drops to zero and charging stops. It can be recovered by dropping to low revs but as I increase the revs the tach drops off again. The obvious candidate is belt slip but there is no sign of belt damage and the alt seems to be spinning OK so I am wondering if something else could cause the same symptoms before I invest in a belt doubling kit. One mechanic pointed out that there is not much contact area on the alt so the doubling kit might be the answer.

I am not too worried about losing the charge, the solar is keeping up fine. I AM worried about losing the belt / water pump - particularly as I am heading down the NY East River in a couple of days...... Is there any way of making an alternator freewheel? Then it can just act as a tensioner until I can get this sorted.

Anyway, thanks for any input!

Graham (enroute to The Bahamas)
 

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Have you noticed if the Balmar is 'lit up' during the dead times? A bad connection on the power wire to the Balmar will give you this symptom.. something intermittent/vibration based??
 

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Yes, check especially the connections and the fuses/fuse holders on the front of the MC-612.

Note also that you can fit a simple on-off toggle switch to the MC-612 which will cut the alternator's output in half whenever desired.

You can also de-rate the alternator by any desired percentage by programming the MC-612. These mods are described in the Balmar manual.

Bill
 

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This has been an issue since I bought the boat and three yards have expensively failed to fix it. I have a Yanmar JH series engine with a large AMP alternator regulated by a Balmar Maxcharge MC-612 reg.

At tickover and during early running all is well. The system charges and the tachometer works normally. After a while the tachometer drops to zero and charging stops. It can be recovered by dropping to low revs but as I increase the revs the tach drops off again. The obvious candidate is belt slip but there is no sign of belt damage and the alt seems to be spinning OK so I am wondering if something else could cause the same symptoms before I invest in a belt doubling kit. One mechanic pointed out that there is not much contact area on the alt so the doubling kit might be the answer.

I am not too worried about losing the charge, the solar is keeping up fine. I AM worried about losing the belt / water pump - particularly as I am heading down the NY East River in a couple of days...... Is there any way of making an alternator freewheel? Then it can just act as a tensioner until I can get this sorted.

Anyway, thanks for any input!

Graham (enroute to The Bahamas)
Beyond the other tips, turn off your solar, turn on some DC loads and let us know if this still happens....

Sounds to me like your solar controller has a higher absorption voltage than the reg thus it may be shutting it down when your are in the upper 90's SOC...

If that test works simply turn off solar if you want to keep the tach or up the voltage setting of the reg...

If this is happening in bulk mode then it is likely a bad reg or connection..
 

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Discussion Starter #6
OK it is not the belt. No change in rotation, no noise, no extra heat. It did only happen when the battery was nearly charged so I have turned off the solar and put some load on. I will monitor and report back. Looks like I don't need a yard right now :).

Thank you all so much for being there. This is our first BIG sailing adventure and we are learning as fast as we can but we are still a little anxious.

Graham
 

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Discussion Starter #7
Not a single hint of a problem since we turned off the solar. Thanks MainSail! I need to set both chargers up more precisely for the new batteries so I will fix it then. Right now turning off is just fine.

Graham
 
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