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Old 15-09-2013, 04:08   #1
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75A or 110A alternators on 110hp Yanmar

We are in final stages of building a 60 ft cat. We will be running 2 x 110Hp Yanmars onboard.We will have 24V/ 800ah battery bank. Besides the extra purchase price of the alternators, is there any reason why I should use 24v/75A alternators instead of 24v/110A alternators?

Thanks for your help
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Old 15-09-2013, 04:27   #2
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Re: 75A or 110A alternators on 110hp Yanmar

no, use the larger ones, always, if you can afford them.
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Old 15-09-2013, 08:22   #3
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Depends on how you will use your house bank, and if you will rely on the alts for charging. But as a general rule, the larger wont hurt a thing, and will lead to faster charge times.
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Old 15-09-2013, 08:37   #4
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Re: 75A or 110A alternators on 110hp Yanmar

Hello, I put the 110 A/24 volt Leece-Neville alternator on my 85 hp Isuzu. These alternators are a great bang for the buck, used in heavy trucks, ambulances, etc. They have a lot of mass to absorb heat and have a handy kit to bypass the regulator to hook up a "smart " one if you want. I think I paid around $350 for it. That and a spare, $700, Compare that to a Balmar!

cheers, Greg
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Old 15-09-2013, 08:43   #5
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Re: 75A or 110A alternators on 110hp Yanmar

Remember that a 75A alt will only run at 75A for a very short time and will probably settle out at 50A if a factory alt and about 60-65A if a true high output design. If run at these outputs for long periods they can be damaged from heat if temp sensing is not utilized. Same for the 110A..

Personally if I was designing that system there would be serpentine/ribbed belts and 140 - 160A alts with external regulation, temp sensors and cross over redundancy management.

About the max a 160A alt can be driven, and not go into temp limiting, when driving at full bulk, is about 120A. People often assume the face value rating is what the alt will actually produce but they won't, for very long...
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Old 15-09-2013, 08:51   #6
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Re: 75A or 110A alternators on 110hp Yanmar

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People often assume the face value rating is what the alt will actually produce but they won't, for very long...
Yes, often overlooked! Often not known or understood is the copper wire used in the armature has a positive temperature coefficient that increases the wire resistance as it heats. And the hotter it gets, the higher the resistance which for a given current will continue to make it hotter. If that internal heat cannot be removed, over time the wire will fail.
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Old 15-09-2013, 08:52   #7
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Re: 75A or 110A alternators on 110hp Yanmar

Consider

110 A x 24 v = 2640 W
2640 W = 2.6 kW
2.6 kW x 1.34 hp/kW = 3.5 hp (each alternator)

You will need very strong alternator brackets and good belt systems (i.e., not v-belts) to drive this at full load. Even the 75 A units (at 2.4 hp each) are large mechanical loads.
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Old 15-09-2013, 09:16   #8
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Re: 75A or 110A alternators on 110hp Yanmar

Big engines, big batteries, big alternators.

b.
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Old 15-09-2013, 09:30   #9
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Re: 75A or 110A alternators on 110hp Yanmar

We have a 170 amp alternator on our 100 hp Yanmar (4JH3-HTE). It is driven by two A43 belts - regular car belts you can buy at any auto parts store. This is in addition to the regular alternator on the engine which charges the starter battery. The big alternator works perfectly so your choice of upsizing to 110 amps, if properly installed, will not stress the engine at all.

A big solid bracket will need to be fitted and, of course, make sure the engine room has a blower.

Cheers.

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Old 15-09-2013, 09:30   #10
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Re: 75A or 110A alternators on 110hp Yanmar

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Originally Posted by Maine Sail View Post

Personally if I was designing that system there would be serpentine/ribbed belts and 140 - 160A alts with external regulation, temp sensors and cross over redundancy management.
I would install a 200A and derate it to 150A.

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Old 15-09-2013, 09:40   #11
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Re: 75A or 110A alternators on 110hp Yanmar

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We have a 170 amp alternator on our 100 hp Yanmar (4JH3-HTE). It is driven by two A43 belts - regular car belts you can buy at any auto parts store. ...
Remember the OP is talking about 24 volt alternators. Twice the load per Amp than 12 volt alternators. His 110A units would equal 220A units at 12 volt. These are big loads.
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Old 15-09-2013, 12:38   #12
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Re: 75A or 110A alternators on 110hp Yanmar

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I would install a 200A and derate it to 150A.

Mark

Even better. The only issue with a 200A alt is the cut in speed. A 160 -140A alt will cut in a little earlier but this is not a big deal so far as the owner knows when it cuts in.

I derate almost all the alts I install as they simply last longer and can be dialed in to run right on the edge of 200-225 degrees all day long, at the max output they can safely handle, long term.. I do this with the "belt manager" feature withing the Balmar regulators.

If you opt for alternator temp limiting every time the alt exceeds temp the output is cut by 50%. Alt temp limiting is a agreat back up to a derate but really digs into charging efficiency, if that is all you use. With temp limiting alt cools and it pops back to full output, then drops again to 50%, then cools then repeats over and over........ It is far more efficient to run a larger alt and then derate it so it stays cool and runs at its max temp ability in that engine bay. Rather than tax a small alt, or to depend solely upon the regulators temp limiting feature, I much prefer to oversize the alt then derate it..

I just had a customer come back from Newfoundland where his 22k brand new generator failed, his back up Honda failed, his solar was insufficient for the loads, but the 120A alt I recently installed, and derated to 85A, saved their entire trip. It would run at 85A for up to four hours straight, because it could. This alt was never meant to be the primary charge source but it became the primary charge source and proved to be 100% reliable due to the features of the Balmar MC-614 regulator.....
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Old 15-09-2013, 14:27   #13
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Re: 75A or 110A alternators on 110hp Yanmar

Before we started cruising I upgrade the original Balmar 80 Alternator.

We have a Yanmar 75hp with an Electromaax 160amp (12v) alternator. Electromaax has a serpentine belt kit and external regulator that provides great power and no slippage.

I would put the largest alternator on your engines you can afford and not reduce HP significantly.

Check out Electromaax they have great equipment!
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Old 15-09-2013, 16:48   #14
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Re: 75A or 110A alternators on 110hp Yanmar

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Check out Electromaax they have great equipment!
I'm glad you are satisfied (really!), but if anyone wants a tale of a complete opposite experience with this company, along with some inside information of very nasty business practices and principles, then give me a shout.

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Old 15-09-2013, 16:49   #15
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Re: 75A or 110A alternators on 110hp Yanmar

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The only issue with a 200A alt is the cut in speed. A 160 -140A alt will cut in a little earlier but this is not a big deal so far as the owner knows when it cuts in.
That can be managed with pulley ratios.

Mark
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