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  #1  
Old 06-08-2008
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Alternator switch

I have a large balmor alternater on a small yanmar.
I saw somewhere a pannel switch that would cut out the alternater or reduce it by 50%. I know from instaling this that I could just put in a inline switch. But the pre made one would look so much better. Any one know where I can get one?? Many thanks again.
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Old 06-08-2008
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On our previous two boats and our current boat, the ignition switch cuts off the alternator in the off postion. I"m not familiar with a switch that reduces output by 50%.

The fancy regulators on our previous boat and current boat both let the engine run for a minute before it ramps up the alternator. If the engine is cold, I regularly start the motor. Run it just long enough to confirm oil pressure came on and raw water is pumping then I shut off the ignition key and let the motor warm up a few minutes. Then I rev it up a bit and turn the ignition back on so that the alternator will engage. A high output alternator certainly puts a noticeable load on the motor when it comes online.
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Old 06-08-2008
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I'm not sure why you would want to reduce alternator output. With a simple regulator, once the batteries are up to 14.4V the alternator is just taking a bit more than friction loads from the engine. Below that you want it charging. With a complicated regulator, it's going to bring the batteries back up much faster, before it also ends up trickle charging, plus friction loads. What is a switch going to do for you, except leave your batteries uncharged?
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Old 06-08-2008
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I just have a 3 way switch for internal, off and external regulators.
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Old 06-08-2008
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Idiens - If you have a small motor, large alternator, cutting the alternator out gives you a few more RPM if you need them.
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Old 06-08-2008
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Would you trade a few rpm for uncharged batteries? I guess whoever put a 100 amp machine on a tiny Yanmar had a reason. Does 15 V x 100 amps = 1500 Watts, or about 2 hp. Ok inefficiency loss,4 hp then. How small is your Yanmar badsanta?
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I have had my boat for about 2 months now and just got back from spending the whole weekend on it, running the fridge, water pumps, stereo and all of the other electronics. I have 3 group 27 gel cells for my house bank and the lowest they got was this morning they were at 12.05 volts. I decided to start the motor up to charge them up a little and once I switched the selector from the 1 starter battery to the house bank, you could def hear the motor start to strain and a squeeking noise coming from prob one of the belts. I shut it down and re-started it under the house bank, reved it up in neutral to 1100 rpms and it seemed to be fine. I have a 24hp yanmar and a 80 amp balmar alternator.

This was the first time I ever ran the batteries down that low and I could def hear the engine straining when I first started charging. Once I kept the revs high though I was fine but I can see how an alternator can put some strain on a small motor.
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Old 06-08-2008
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An 80A alternator would put less than 2HP strain at full output. This shouldn't be a problem for a 26HP Yanmar, or most any other small engine. If you're hearing some belt noise or other sounds, you might check your system to see what's up.

My 4-108 handles a 110A alternator on a single belt (same one as the water pump) just fine, at idle or at speed. NB: the 4-108 is variously "rated" at 40, 47, or 50HP, but these are gross exaggerations of its real power, which some have estimated at about 30HP for all practical purposes.

The Balmar MaxCharge MC-612 has a feature where you can install an external switch which will reduce the charge amount by approx. 50%.

Bill
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Old 06-08-2008
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There are various reasons somebody might want to cut alternator load/output. If the engine is overheating, if you're low on fuel and need maximum efficiency/range, if you're bucking a really serious current and need everything you can get from the engine, etc etc.

And it's not just the engine size at issue. A 24 hp engine may have no problem with the 80 or 100 amp alternator in theory, especially if it's on a lightweight, low-wetted surface, easily driven hull. But if that same engine is on the small size for the boat it's in -- like a heavy, full keeler -- you're more likely to have need to call on all it's got under certain circumstances.

The Balmar smart regulators (like the MC-612) have optional temperature sensors to the battery and alternator. If the alternator temp sensor detects an over-heat condition, the regulator automatically cuts alternator output in half until it cools down. By placing an in-line switch in this sensor wire, you can simulate the over-heat condition and reduce alt output/load on demand. This is the switch Badsanta is asking about.

Unfortunately, I'm unaware of the special one he is talking about. I purchased a basic Cole-Hersee waterproof toggle switch for our previous boat, with the intention of doing exactly as BadSanta plans, but we sold the boat before I got around to that project.
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Old 06-17-2008
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Thanks for the info. More info about my system. I have had no real problems yet, But I am also a little over propped. I have a 110 amp balmar with the max charge 612. I have 4- 250 amp AGM batteries. What I wanted to do If I needed the power in bad weather of stiff currents was to be able to reduce the alternator if it really had a charging load but needed to movethe prop first. I understand the switch on the temp sensor. I just thought it would be nicer to have a premade panel insted of a couple of toggels. But thanks for the info. Al
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