Upgrading alternator

[Nyssa]

I have a Yanmar 3GM30F (27HP). It is fitted with the stock 55 amp Hitachi alternator which I want to upgrade to a high output unit with an external smart regulator. I was looking at the Balmar range. Can anyone tell me what model would suit? I am looking for something that will fit the existing brackets/mounts and not place too much demand on engine. Thanks!

[GordMay]

The Balmar 60 & 70-Series (70 - 100 Amp) Dual Foot Mount (3.15" saddle) c/w ½" diameter belt pulleys (not standard 3/8") are generally recommended as replacements for Yanmar’s OEM Hitachi alternators.

http://www.balmar.net/PDF/Alternator...naldrawing.pdf

http://www.balmar.net/PDF/Alternator...naldrawing.pdf

Yanmar offers a 80 amp and 115 amp alternator option for the 3GM30F.

Yanmar alternators (Hitachi) are N type and are internally regulated.
All Balmar alternators are externally regulated P-type.


You're looking at a LOT of $ with Balmar.

[Nyssa]

Thanks Gord May. A couple of related questions. My batteries are AGM 4 x 100 ah for house and 1 x 100 ah for start. The boat is on a mooring when not sailing. A 30 watt solar panel nicely maintains the house bank. Any thoughts on output I should go for - 80 amp, 100 amp etc. And if Balmar is too pricey, what else would you recommend. Finally, as part of the same upgrade I was looking at putting an echo charger in connecting the start and house banks. I read somewhere here (but haven't been able to find the posts again) that it may not be a good idea to link the alternator to the start and then echo charge the house from the start? I thought it would be better to charge start first and then the house? Can you tell me if there is anything wrong with that? Thanks for sharing your expertise with me.

[Hud3]

You might as well go for the 100 Amp alternator with a 400 AH house bank. The bigger, the better. Charge the house bank with the alternator, and use a Balmar Digital Duo Charge unit to keep the start battery charged from the house bank. That's the way my system is set up. Doing it the other way doesn't make any sense at all to me.

[Nyssa]

What is the rationale behind charging the house bank and echo charging the starter? Is there a problem with doing it the other way around? Wouldn't it mean that the start battery is less vulnerable to running down if it gets the direct/main charge? Just interested in the different approaches.

[AnchorageGuy]

The Echo charger is designed to put out fewer amps for shorter periods of time and not suitable for larger house banks. The starting battery uses enough power to start the engine than is recharged and stays that way. The house bank is almost constantly under demand and needs the main charging source form the alternator or battery charger. It would make little sense to do it the other way around.

[Vasco]

It's hard to find a good cheap HO alternator especially a saddle mount one which the Yanmar needs. I like Powerline but they're not cheap either. Remember besides the cost of the alternator you'll need an external regulator and may need to upgrade the wiring.This is important if you don't want the works to go up in flames.

[btrayfors]

Most sailors don't stop to figure the actual amperage draw of their start batteries. A little math is an eye-opener:

Typical Energy Usage on a 40-foot Sailboat per Day

House batteries: somewhere between 100 and 200 amp hours

Start battery (assuming 2 engine starts/day): total of 2 amp hours!

Figure: 250 amps starting current for 15 seconds per start (most engines take far less than that). But, for illustration, figure 30 seconds total starter time to start the engine twice a day.

250 amps x 1 hour would be 250 AH
250 amps x 1 minute would be 250AH/60 minutes = 4.2 AH
250 amps x 30 seconds would be half that, or 2.1 AH

Nothing, really, in the larger scheme of things.

These two AH are replaced in mere seconds after the engine starts.

THAT's why it's good practice to connect all onboard charging sources to the house batteries, and use a device like an EchoCharge or a DuoCharge to bleed off a bit of the charge current to top off the starting battery.

Bill

[Nyssa]

I get it. Thanks for taking the time to spell it out for me. I guess my way of thinking has always been to take care of the start battery first, house second.

[GordMay]

Approximate Rule of Thumb:
25 Amps of Alternator Output = ± 1 H.P. of Engine Power

The horsepower draw of an alternator is directly proportional to the electrical & mechanical efficiency of the alternator & drive (belts), and to the output level (amperage being drawn from it).

Many alternator systems are about 50% efficient at full rated output, as installed.

One horsepower equals 746 watts. (Actually 1 horsepower = 745.699872 watts)
(Watts ÷ Volts) x Efficiency = Amps
Hence 1 Horsepower = about 25 Amps of Alternator output (@ 12V Nom.).
(746 W ÷ 14 V) x 0.50 eff. = 53.28 x 0.50 = 26.64 A

Accordingly, a 55A Alternator will “use up” about 2 Horsepower, and a 100A alternator will use about 4 H.P. at full output.

[witzgall]

I just read the doc on the Duo Charge, and it left me with question. If you are using one of these, could you, would you, have a traditional battery switch with positions for your house and starting battery (1&2)?

Chris