Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 06-10-2016, 01:39   #1
Registered User

Join Date: Feb 2009
Posts: 68
How to determine maximum size of alternator

I have a Yanmar 4JH57 engine. The primary alternator is the original Valeo 120 amp. I am planning to add a secondary alternator. My first choice is a mastervolt 130 amp unit. I have one already and it will suit my purpose well which is to charge a mastervolt lithium house bank. But it is a big beast. It weights 10 kg and its physical dimensions are approximately 2-3 times larger then the Valeo. I have a choice to downsize to a mastervolt 90 amp alternator which comes in around 5 kg. Does anyone have any guidance when designing a two alternator set up? Specifically, is it a bad idea to have a much heavier alternator on one side of the engine then the other side.

Thanks






Sent from my iPad using Cruisers Sailing Forum
__________________

__________________
HKTim is offline   Reply With Quote
Old 06-10-2016, 01:57   #2
Registered User

Join Date: Nov 2014
Location: Norway / Oslo
Boat: Jeanneau 42 DS
Posts: 96
Re: How to determine maximum size of alternator

You have to messure if you can fit the lage alternator.
We have one Balmar 200A and one Balmar 150A fited on an 4JH4AE.

Dont have any experience with the mastervolt alternators but they seem very good and Mastervolt also claim they are rated for continius power, Balmar is not.

You can use the Mastervolt regulator on most alternators but you have to convert it to negative controll.

(We have 1000AH winston Lifepo4 and the Mastervolt mass combo ultra 3000-150.)
Attached Thumbnails
Click image for larger version

Name:	balmar_200a.jpg
Views:	182
Size:	86.9 KB
ID:	132393   Click image for larger version

Name:	20161001_165705.jpg
Views:	150
Size:	353.4 KB
ID:	132394  

__________________

__________________
offpist is offline   Reply With Quote
Old 06-10-2016, 02:11   #3
Registered User

Join Date: Feb 2009
Posts: 68
Re: How to determine maximum size of alternator

Thanks. I have plenty of space so that is not a concern. My concern is if there will be a problem hanging a 10 kg alternator off one side of engine shaft against a 3-4 kg alternator on the other side. I need to have a custom mounting bracket built but when discussing this with my mechanic he said his preference is to use similar weight alternators in this kind of set up. So am trying to verify if he has raised a valid concern.

Thanks


Sent from my iPhone using Cruisers Sailing Forum
__________________
HKTim is offline   Reply With Quote
Old 06-10-2016, 05:16   #4
Registered User

Join Date: Aug 2015
Posts: 175
Re: How to determine maximum size of alternator

The 4JH57 should be fitted with a serpentine belt from the factory so side load should be reasonable. High output alternator are large because they need to dissipate lots of heat, especially if charging batteries that can accept huge current (like lithium). Make sure the mounting brackets are robust and you should be ok.
__________________
boatbod is online now   Reply With Quote
Old 06-10-2016, 09:18   #5
Registered User

Join Date: Jul 2015
Posts: 234
Re: How to determine maximum size of alternator

Quote:
Originally Posted by offpist View Post
Dont have any experience with the mastervolt alternators but they seem very good and Mastervolt also claim they are rated for continius power, Balmar is not.
Not doubting your word, but are you sure Mastervolt clearly claims they are rated for "continuous power." I looked at both the 130/12's and the specs allude to low RPM output - but nothing ironclad and no figures given in the spec sheets I read. Just have never seen an alternator that could do full rated output across the board at all RPM's. FWIW, that doesn't mean one doesn't exist!

I always get a little concerned when the marketing and advertising people get creative
__________________
crabcake is online now   Reply With Quote
Old 06-10-2016, 09:21   #6
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,266
Re: How to determine maximum size of alternator

I don't know the output of that Yanmar, but I gather it's up there. Be aware that altenator loads, particularly from big ones, are parasitic loads on the drivetrain. You may create problems not only from obvious sources, such as wear on the internals, but in terms of lost output at the prop end; effectively you are changing your 'real" as opposed to rated power/torque curve. You may find 2,100 RPM (or whatever) does not move you as fast in flat water as it did before the big alt's "friction".

Solutions may include a prop repitching or simply monitoring your usage or having an alternator disconnect method.

That said, maybe you will end up working your engine right to spec. Most people do not. A good way to tell is to install an exhaust gas temperature (EGT) monitor. It's cheap insurance against overworking your engine.
__________________
Can't sleep? Read www.alchemy2009.blogspot.com for fast relief. Can't read? Avoid www.volumesofsalt.blogspot.com, because it's just personal reviews of sea books.
S/V Alchemy is offline   Reply With Quote
Old 06-10-2016, 09:24   #7
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,266
Re: How to determine maximum size of alternator

Quote:
Originally Posted by crabcake View Post
Not doubting your word, but are you sure Mastervolt clearly claims they are rated for "continuous power." I looked at both the 130/12's and the specs allude to low RPM output - but nothing ironclad and no figures given in the spec sheets I read. Just have never seen an alternator that could do full rated output across the board at all RPM's. FWIW, that doesn't mean one doesn't exist!

I always get a little concerned when the marketing and advertising people get creative
Yes, so do I. External regulation gives you fewer amps at the chosen voltage with less heat and chance of damage. I would prefer that to a blazing hot alternator. I've tried to plan my energy requirements so it is essentially supplemental to solar and wind, meaning "intermittent power for years and years" is far preferable. Besides, you size this stuff to the acceptance rate of the bank, otherwise it's a case of "fat guy in a sitz bath".
__________________
Can't sleep? Read www.alchemy2009.blogspot.com for fast relief. Can't read? Avoid www.volumesofsalt.blogspot.com, because it's just personal reviews of sea books.
S/V Alchemy is offline   Reply With Quote
Old 06-10-2016, 11:58   #8
Registered User

Join Date: May 2013
Posts: 8
Re: How to determine maximum size of alternator

The physical size of the alternator should make no difference as long as it is correctly installed and the belt tension is right. Depending on the state of charge of the battery bank the alternator will use up to 2.5 horsepower under a full load (discharged battery bank)
__________________
scubano is offline   Reply With Quote
Old 06-10-2016, 12:12   #9
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 17,466
Re: How to determine maximum size of alternator

I don't think the weight of the alternator is an issue... assuming you can design a proper bracket anyway. The side load is caused more by the amperage of the alternator on the belts right?
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 06-10-2016, 12:14   #10
Registered User

Join Date: Jun 2013
Location: canada
Posts: 1,359
Re: How to determine maximum size of alternator

Quote:
Originally Posted by crabcake View Post
Not doubting your word, but are you sure Mastervolt clearly claims they are rated for "continuous power." I looked at both the 130/12's and the specs allude to low RPM output - but nothing ironclad and no figures given in the spec sheets I read. Just have never seen an alternator that could do full rated output across the board at all RPM's. FWIW, that doesn't mean one doesn't exist!

I always get a little concerned when the marketing and advertising people get creative

continuous power means you can run it full output for hours or days. most alts will get hot and lower output over time.

no alt will put out max power at idle. that is not what they are stating.


I don't see how the weight has any effect, other them making brackets strong enough. this has nothing to due with the shaft at all. the belts will see a 120a load on one side and a 130a load on the other. almost the exact same. the weight is only for heat disapation
__________________
smac999 is online now   Reply With Quote
Old 06-10-2016, 13:17   #11
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Hanging with the owner's daughter ;)
Boat: Anything entertaining.
Posts: 3,129
Re: How to determine maximum size of alternator

What your mechanic may be referring to, in perhaps poorly chosen words, is that theoretically, if you mount 2 alternators of the same size on an engine 180 deg. apart from each other, then the pull on the seals & bearings in the engine from them is negated. Whereas if you have 2 alternators on an engine that are different sizes, & mounted obtusely in relation to each other, then they could cause some components in the engine to die prematurely. But as to how fast this "death" may happen I can't even begin to guess at.

I can't say that I know how factual the above statement, & theory is. But I've seen it in more than a couple of places. And it might be worth researching. Including on different forums oriented specifically towards engines & such.

Though I do wonder about it's veracity a bit, given that in millions upon millions of cars, there are multiple belts on the engine for power take off, led at odd angles to various sized loads. Such as the AC compressor, alternator, & water pump, etc. Most of which exert a not insubstantial sideways loading on the power take off pulley. Yet these engines run for tens & hundreds of thousands of miles without issues from this. So then, are marine diesels so much more fragile than these automobile engines?

I'm curious, is your mechanic one who works on boats a lot? So that he has enough depth of knowledge from which to form conclusions like the above. If in fact that's what he's trying to tell you.
Also, I can't help but to wonder how some other diesels have their power take offs for other systems setup. Such as those on an 18-wheeler, whose engine has to power a multiplicity of heavy sub-loads.

If you find out much could you please post it here on the forums. It would likely benefit many of us. And a bibliography of relevant informational links would be great.

Edit: One thing which would definitely make sense, is to have two alternators that are parts compatible with one another. That way if both of them go down in the middle of nowhere, then you may be able to cannibalize components from them in order to get one up & running.


offpist, that engine of yours is so clean that it looks like a computer generated image, or a pic that's been "tuned" via photo editing software. Dang!
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is offline   Reply With Quote
Old 06-10-2016, 13:34   #12
Registered User

Join Date: Nov 2014
Location: Norway / Oslo
Boat: Jeanneau 42 DS
Posts: 96
Re: How to determine maximum size of alternator

Quote:
Originally Posted by UNCIVILIZED View Post
offpist, that engine of yours is so clean that it looks like a computer generated image, or a pic that's been "tuned" via photo editing software. Dang!
Thanks. That engine has been arround the world and has 5200 hours on it. Still going strong.
__________________
offpist is offline   Reply With Quote
Old 06-10-2016, 15:52   #13
Registered User

Join Date: Mar 2016
Posts: 11
Re: How to determine maximum size of alternator

S/V Alchemy, I am not as knowledgable as you but wonder why 2100 rpm with heavy generation would be slower than 2100 with small generation. Wouldn't psame prop rpm give same speed?
__________________
Inhancer is offline   Reply With Quote
Old 07-10-2016, 08:26   #14
Registered User

Join Date: Oct 2010
Posts: 116
Re: How to determine maximum size of alternator

Quote:
Originally Posted by Inhancer View Post
S/V Alchemy, I am not as knowledgable as you but wonder why 2100 rpm with heavy generation would be slower than 2100 with small generation. Wouldn't psame prop rpm give same speed?

Yes speed will be the same.

With regards to load on the engine as a rule of thumb absorb twice as much with a 30% increment in speed. So if your engine can produce 50hp at max Rpm of 3000rpm and the prop is correctly match the prop will absorb 50hp at 3000rpm. At 2300rpm the prop will absorb 25hp and at 1800rpm 13hp. At 2300rpm your engine may have the ability to produce say 35hp at the crank, 10hp more than the prop can absorb so an additional alternator will present no issues at this rpm but you will use slightly more fuel.

At close to max rpm the additional alternator could overload the engine. Crankshaft vs prop hp charts at various rpm are normally on the manufacturers websites.


Sent from my iPad using Cruisers Sailing Forum
__________________
John Holbrook is offline   Reply With Quote
Old 07-10-2016, 19:22   #15
Registered User

Join Date: Oct 2009
Location: Redondo Beach, CA
Boat: 1990 Oyster 55
Posts: 238
Re: How to determine maximum size of alternator

Quote:
Originally Posted by John Holbrook View Post
Yes speed will be the same.

With regards to load on the engine as a rule of thumb absorb twice as much with a 30% increment in speed. So if your engine can produce 50hp at max Rpm of 3000rpm and the prop is correctly match the prop will absorb 50hp at 3000rpm. At 2300rpm the prop will absorb 25hp and at 1800rpm 13hp. At 2300rpm your engine may have the ability to produce say 35hp at the crank, 10hp more than the prop can absorb so an additional alternator will present no issues at this rpm but you will use slightly more fuel.

At close to max rpm the additional alternator could overload the engine. Crankshaft vs prop hp charts at various rpm are normally on the manufacturers websites.


Sent from my iPad using Cruisers Sailing Forum
Well put

Sent from my SM-G935V using Cruisers Sailing Forum mobile app
__________________

__________________
botanybay is offline   Reply With Quote
Reply

Tags
alternator, maxi, size

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
450: Maximum size for dinghy / rib on Lagoon 450 caymancat Lagoon Catamarans 1 04-10-2016 21:04
78 pearson 30 maximum allowable prop size simplynick912 Propellers & Drive Systems 8 26-02-2013 17:11
Maximum Range of Boats this Size . . . SotorMailer Monohull Sailboats 11 03-09-2010 07:48
Hurricane Maximum CPA blahman Navigation 9 20-11-2006 18:49
Maximum draught for Cruising - 7'6" too deep ? ribbony General Sailing Forum 4 13-03-2006 20:11


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:50.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.