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Old 28-02-2009, 14:11   #1
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I a stock Yanmar 55a Alternator "heavy-duty" enough to be changed to external reg?

Hi folks,

I have read alot on changing to "high-Output" alternators, such as Balmar, etc.

I have a Yanmar 2GM , with the stock 35a. I am looking to buy a larger (approx 55 - 70a) alternator, and likely purchasing an external 3 stage regulator, to go with it.

I would keep my current 35a model for a spare.

If I have a stock (say 55a) alternator rewired, to accept an external regulator, I assume that it will then put out higher voltage or amps, when bulk charging - Could this lead to overheating, as it was designed to work with the internal regulator, which likely charged / put out less, and therefore "worked" the alternator less?

Any input would be appreciated!

I have a house bank with 2 group 27s, and a start group 24. Fairly modest electrical needs. New Iota 45a for dockside charging, but woudl like to be more efficient when away from dock for a few days at a time.
Coastal cruising only.
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Old 28-02-2009, 15:58   #2
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NE, first check the specs. of the internal regulator on your proposed alternator, on my Hitachi 55A alternator (that came fitted to my 2GM20), the internal regulator is set to 14.5 V.

While there are certain benefits to be had with external regulators (single or multistage), a reasonable output alternator (50 to 70 Amps as you suggest) with a stock 14.5 V internal regulator would properly do the job in your circumstances quite well.
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Old 28-02-2009, 16:29   #3
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Wot - thanks for the reply. I don't have the specs on me, but they would likely be close to that of your's. I have read everywhere how the 3 stage regulators are so much better than the internal, and that's why I was looking in that direction. Regardless of internal or external, I do plan to get a larger one, or possibly have mine rewired to produce more.

I like the idea of having my old one, for a spare. I will be charging at the dock mostly, other than a couple week cruise, and some multi day trips, in the summer. The external regs are not cheap, so I may try to get by with an internal one.
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Old 28-02-2009, 16:59   #4
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I will post a link in a couple days time that deals with the common misconceptions of internal regulators if you like (I don't have it available right now). I should know, I held most of them

The Hitachi alternator is quite easy to modify to take an external regulator if you are reasonably confident and can solder. I have the details at home but not with me now.

The principal advantage of the 3 stage regulator is that they can bulk charge the battery and then switch to a float charge when the battery requires it. Have a look in the electrical section stickies.

The common misconception is that internal regulators won't bulk charge a battery, that they are all set for 13.8 to 14 volts. This is simply not true, it may have been once, but some (many?) internal regulators are now set around 14.5 volts. While not a perfect solution, it is a workable compromise.

Most battery problems are due to undercharging rather than overcharging. A 14.5 V internal regulator goes a long way to addressing this problem.
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Old 28-02-2009, 17:33   #5
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Wot - great info. And Yes, I would be interested in any more info you could provide!!

Thanks again!
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Old 28-02-2009, 17:40   #6
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I guess I am also still wondering if the Balmar type (high output) alts have heavier windings, etc, than their similar amp rated auto counterparts, for example.

As I have read that auto alternators (wiith internal regs) are designed to shut on and off continuously (as not to overcharge the one car battery) - would they be capable of withstanding the extra burden placed on them, if they were charging a deep cycle bank (via an internal, or external regulator).

Just wondering if I should be looking at a stock 55a - 70a Yanmar alt, Balmar, Leece- Neville, etc. Is there really any difference among different brands of say 55a alternators??
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Old 28-02-2009, 17:59   #7
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NE, I will home in a couple of days and will try to remember to post a link etc. Please feel free to remind me if I forget .

I can't help with info on alternators as I have never seen any duty cycle or temperature specs. on them but I am sure someone on CF should know.

I do know that it is the temperature that is the killer. High output equals high temp. Top end units have temperature sensors that shut down the output as required.

However you state your electrical loads are modest so it sounds to me like a 50 to 70 A unit would be fine if the supplied regulator is around 14.5 V but this is just an opinion rather than knowledge talking .
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Old 28-02-2009, 18:13   #8
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If you are only going to be away from the dock for 2 or 3 days at a time, not doing a whole lot of motoring, don't bother to upgrade. What you have will get you by just fine (so long as you can live on the 2 battery energy budget). I am a big proponent of external regulators and larger alternators for serious cruising. If you said that you were going out for 2 or 3 weeks I would advise you to upgrade.

Have fun.
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Old 28-02-2009, 18:38   #9
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To answer your question if there are differences, yes there are. I think that the Hitachi alternators are good ones. I don't have the specs. but they are always highly rated on the forums. Some alternators have a "hot" rating, which states the amp. output at a certain temperature. Some are rated cold but they cannot sustain that output for long. You have to really search to find the true ratings. Leece Neville are also very highly rated. Most of them are internally regulated I believe.
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Old 01-03-2009, 07:40   #10
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DeepFrz- Thanks for the info!

We have a months vacation in the summer, and will likely spend 2-3 weeks of that crusing around Nova Scotia, and the inland Bras D'Or lakes. The rest of the season will be spent near the dock, away for mostly weekends, or day sailing.

Our electical needs are modest:
- Raymarine C80 Chartoplotter - on 99% of sailing time.
- may get radar this year

- pressure water system
- VHF
- older cabin lights
- bilge pump

- NO Fridge - just large icebox
- NO AC or heater

I only bought the new Iota charger at the end of season last year, so we got by just with alternator last year. Likely wasn't good for batteries, as they were probably undercharged. Thsi year, will be charged well at the dock.
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Old 01-03-2009, 10:21   #11
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I still REALLY like my portable generator as opposed to upgrading my alternator(s). Great thing is it has come in handy when I took it off the boat and lost power at home. Kept all the food from going bad when we lost power for a day and a half. (Power company broke a transformer!)
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Old 01-03-2009, 14:28   #12
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Was / am considering a portable generator. However, the cockpit lockers on my boat are not airtight / separate from the cabin. I would have to store it on deck, strapped down in front of the mast, or something like that, for fear of having gas fumes / risk of explosion in the cabin.

I like the idea of having a generator, in case I drained the batts by mistake, although I normally use bank 2 for all but starting the engine.

I did try to hand start my 2gm last year, with my girlfirend throwing the decompression levers for me. Although I wasn't successful, with only 1 try, I think I could do it in an emergency. Just didn't think it was worth throwing a shoulder out "just to see"!!!
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