Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 29-06-2016, 23:26   #1
Registered User

Join Date: Apr 2007
Location: New England
Boat: lagoon 380 s2
Posts: 493
Which charges my battery faster, generator or altenator

I have a cat with 2 29hp Yanmars. Regular alternators, not Balmar or high capacity, etc.

I also have a 2kw Honda generator. This puts out 15A at 120V, and I have a 40 A battery charger on board.

I would think running both engines say at around 2.5k rpm, which is about best for fuel vs. speed would give me about 2x the amps as the generator.

Is this correct? I am trying to decide if I should bring my generator on cruises, or just rely on the engine to put back the amps. I would think we would run the engines about 2 hours+ a day at a minimum.
__________________

__________________
jbinbi is offline   Reply With Quote
Old 30-06-2016, 00:16   #2
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,385
Re: Which charges my battery faster, generator or altenator

Quote:
Originally Posted by jbinbi View Post
I have a cat with 2 29hp Yanmars. Regular alternators, not Balmar or high capacity, etc.
Yanmar engines usually have Hitachi alternators. Please be aware of the following. Battery bank capacity, and SOC, therefore, acceptance also play a part.

Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

Musings Regarding External Regulation | SailboatOwners.com Forums

and these, too:

Hitachi Alternator and Smart Regulator Instal Question


Most practical way to upgrade Yanmar alternator?
__________________

__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 30-06-2016, 00:19   #3
Registered User

Join Date: Jun 2013
Location: canada
Posts: 1,698
Re: Which charges my battery faster, generator or altenator

Get a 2nd 40a charger and bring the gen.

You can probably run an 80a charger off it. Maybe only a 60.
I would never run an engine for battery charging
__________________
smac999 is offline   Reply With Quote
Old 30-06-2016, 00:45   #4
Registered User

Join Date: Apr 2007
Location: New England
Boat: lagoon 380 s2
Posts: 493
Re: Which charges my battery faster, generator or altenator

Ok.makes good sense, and i will have solar in 2 months as well, but that 2nd cjarger won't happen for another year, so the question still remains, will 2 alternators charge my battery faster than a single 40a charger.

Sent from my SM-G900V using Cruisers Sailing Forum mobile app
__________________
jbinbi is offline   Reply With Quote
Old 30-06-2016, 01:55   #5
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: Which charges my battery faster, generator or altenator

As Stu has pointed out, the Hitachi alternators are not the greatest. I think the 60A unit was standard on the 29 HP.

It depends a bit how your charging is set up. Via a VSR or split diode for example, but generally I would expect that your two alternators at moderate revs should comfortably beat the output of a 40A battery charger. If you are only running one engine the generator/battery charger would win.

The best option would be to measure the output. If you don't have a battery monitor a clamp on multimeter is an easy way to quantify the difference.
__________________
noelex 77 is offline   Reply With Quote
Old 30-06-2016, 09:24   #6
Registered User

Join Date: Nov 2013
Location: Homeport: Oswego, NY
Boat: 1993 Sabre 362 #113
Posts: 351
Re: Which charges my battery faster, generator or altenator

Quote:
Originally Posted by jbinbi View Post
I have a cat with 2 29hp Yanmars. Regular alternators, not Balmar or high capacity, etc.

I also have a 2kw Honda generator. This puts out 15A at 120V, and I have a 40 A battery charger on board.

I would think running both engines say at around 2.5k rpm, which is about best for fuel vs. speed would give me about 2x the amps as the generator.

Is this correct? I am trying to decide if I should bring my generator on cruises, or just rely on the engine to put back the amps. I would think we would run the engines about 2 hours+ a day at a minimum.
Lots of variables here. First, how large is your battery bank? A charger should be sized at 10% of the bank size plus the typical DC draw: lights, radio, etc.

Second, as has been mentioned the stock Hitachi alternators are not that powerful.

Third, going from 50% SoC to 80% SoC happens pretty quickly because the battery can absorb current easily. Once you reach 80% SoC the absorption rate slows down. So, on a 400 AH bank, going from 50% to 80% would require 120 + amps or with a 40 amp charger about 3 hours. But going from 80% to 100% will take much longer, maybe 6 to 8 hours.

Read the posts Stu put up, they are especially informative.
__________________
Dave Lochner is offline   Reply With Quote
Old 30-06-2016, 09:51   #7
Registered User

Join Date: Dec 2013
Location: Rogoznica, Croatia
Boat: Bavaria Cruiser 40
Posts: 619
Images: 16
Re: Which charges my battery faster, generator or altenator

Have a look at Sterling Power's range of Alternator to Battery (A2B) chargers. These units totally change the way the alternator system charges you batteries and makes the system much more effective. Fundamentally they take the "dumb" alternator and turn it into a "smart" charger, well that's how I read the blurb anyway.

Might be the best route and means you don't have to carry the extra generator, extra fuel or worry about the noise of the genset in that secluded anchorage.

Just my 2p worth

Keiron
__________________
kas_1611 is offline   Reply With Quote
Old 30-06-2016, 10:00   #8
Registered User

Join Date: Apr 2007
Location: New England
Boat: lagoon 380 s2
Posts: 493
Re: Which charges my battery faster, generator or altenator

Quote:
Originally Posted by Dave Lochner View Post
Lots of variables here. First, how large is your battery bank? A charger should be sized at 10% of the bank size plus the typical DC draw: lights, radio, etc.

Second, as has been mentioned the stock Hitachi alternators are not that powerful.

Third, going from 50% SoC to 80% SoC happens pretty quickly because the battery can absorb current easily. Once you reach 80% SoC the absorption rate slows down. So, on a 400 AH bank, going from 50% to 80% would require 120 + amps or with a 40 amp charger about 3 hours. But going from 80% to 100% will take much longer, maybe 6 to 8 hours.

Read the posts Stu put up, they are especially informative.
Thanks. Did read Stu's posts, always do, good stuff.

Have 450A bank. If I am using 100A a day, and I can put back that back with both alternators going for 2 hours, good stuff. I will look at the Sterling Power as well. I would rather not have to spend 1k for each balmar.

Actually hoping that the 550W of solar going in a month will mostly take care of this issue. Biggest hold up has been getting a custom frame designed and welded. But that is for a different post....
__________________
jbinbi is offline   Reply With Quote
Old 30-06-2016, 21:59   #9
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,727
Re: Which charges my battery faster, generator or altenator

Quote:
Originally Posted by jbinbi View Post

Have 450A bank. If I am using 100A a day, and I can put back that back with both alternators going for 2 hours, good stuff. I will look at the Sterling Power as well. I would rather not have to spend 1k for each balmar.
You cannot put the 100 AH used each day back in 2 hours.

As posted above 50% to 80% charging can be accomplished quickly as the batteries at this level will accept larger currents. With your 450 AH bank the acceptance during this stage could be as high as 70 to 80 amps or so.

But after the bank is at about 80% SOC their internal resistance rises and they accept less and less current. 80% for your bank is 360 AH remaining. The last 90 AH will take 5 hours or more as the batteries acceptance goes down constantly. When they are accepting about .5% of the bank size they are considered fully charged. This equates to 2.25 amps flowing into the batteries.

This is why charging batteries fully with any engine makes no sense. Most cruisers take their batteries down no further than 50% and if using an engine or generator to charge stop at 80% SOC. They use solar and/or wind generators to put in the remaining AH.

Your solar when it is installed will make all the difference. Batteries die most often from under charging which leads to plate sulfation. At the present time partial charging is your only real choice.
__________________
mitiempo is online now   Reply With Quote
Old 01-07-2016, 02:22   #10
Registered User

Join Date: Nov 2011
Posts: 37
Re: Which charges my battery faster, generator or altenator

As a general comment, I don't see the logic of running big engine/s to charge batteries unless you are planning to motor a lot. (like using a sledge hammer to crack a nut) Running big diesels on low load is not efficient or good for them so using them just to charge batteries might be a very expensive option in the long run. A combination of some of solar/wind/towed generator plus a small diesel generator (that can charge at the max rate the batteries can take) would seem to be the best long term solution? If correctly sized the generator should be able to charge the batteries just as quickly as the main engine.
__________________
quandary is offline   Reply With Quote
Old 01-07-2016, 18:51   #11
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,385
Re: Which charges my battery faster, generator or altenator

Quote:
Originally Posted by jbinbi View Post
I would rather not have to spend 1k for each balmar.
Glad to help, as always.

Don't bother with Balmar alternators unless they are the new ones.

ASE Supply distributes Leece Neville units, pretty good:

just an example

Leece Neville*110-603 - 12V 90 amp ALTERNATOR
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 01-07-2016, 20:10   #12
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat in La Paz)
Boat: Valiant V40
Posts: 432
Re: Which charges my battery faster, generator or altenator

Consider running your existing alternators with a modern external regulator. At least when you motor you can be reasonably certain you will put as many AH into the batteries as you can.

We run our boat on a pretty wimpy 70A alternator with 250 w of solar in the Sea Of Cortez. With all LED lighting, Danfoss 50 refer, computers etc, etc, we are able to maintain without running the engine specifically to charge batteries. Takes a bit of energy management, but not so much as to be obnoxious.
__________________
jamhass is offline   Reply With Quote
Old 01-07-2016, 21:43   #13
Senior Cruiser
 
newhaul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 3,941
Re: Which charges my battery faster, generator or altenator

Quote:
Originally Posted by jbinbi View Post
Thanks. Did read Stu's posts, always do, good stuff.

Have 450A bank. If I am using 100A a day, and I can put back that back with both alternators going for 2 hours, good stuff. I will look at the Sterling Power as well. I would rather not have to spend 1k for each balmar.

Actually hoping that the 550W of solar going in a month will mostly take care of this issue. Biggest hold up has been getting a custom frame designed and welded. But that is for a different post....
I would just charge with the mains for the next couple weeks when you get the solar up and running it should provide about 210 or so ah per day with a couple hours of motoring you say you will need to do each day you will guaranteed have full batts by sundown each day.
Why Cary gasoline for the Honda genny
__________________
Non illigitamus carborundum
newhaul is online now   Reply With Quote
Old 03-07-2016, 05:45   #14
Registered User

Join Date: May 2013
Location: Mystic
Boat: Sabre 38 mkII
Posts: 261
Re: Which charges my battery faster, generator or altenator

There is a ton of good advice here and i would just add that I think you need to start with a battery monitor and a clamp on ammeter... and spend time gathering data.

You need to fully understand what your engines charge at, your generator charges at, and your daily consumption is at anchor, and also underway (assuming you do passages).. and at a minimum scale your solar to match your daily consumption at anchor.

If you are planning extended passages, then seriously consider upscaling the solar, or adding wind, to cover your daily needs while passagemaking.

In my case, my alleged 50A alternator with poor single stage regulation peaked at about 30A, and my daily consumption was about 130-150aH or so underway, and about 50aH at anchor.

I installed a Balmar 100A alternator and 3 stage charger and sure it cost $1k.. and cut my charging time by 2/3... seems to be money well spent.

I spent another $1k on solar/charger and now no longer charge at anchor...seems to be money very well spent.

in summary, charging times of 4hrs per day offshore dropped to 3hrs every two days, and 3hrs every 2 days at anchor dropped to near zero.. meaning I ran the engine almost 300hrs less on the second cruise, saving 150g of diesel...

After this years upcoming cruise, both the balmar and the solar will have pretty much paid for themselves, and i will have missed at least a dozen trips to a fuel dock...

whenever you wish to consider cost.. also consider the benefit
__________________
Mystic38 is offline   Reply With Quote
Old 03-07-2016, 13:08   #15
Registered User
 
Privilege's Avatar

Join Date: Oct 2009
Location: Bermuda
Boat: Privilege 435
Posts: 362
Images: 12
Re: Which charges my battery faster, generator or altenator

I recently did some comparison calculations on this subject, trying to figure out which was the more economical method to recharge my batteries so thought I'd share with the group.

I have twin Yanmar 54hp 4JH3's. One of them is fitted with a high output alternator which charges the house bank through a Balmar intelligent multi-stage charge controller. (The other is dedicated to charging the starting and anchor windlass batteries).

I also have a Next-Gen 3.5kw diesel generator running at 2800rpm.

I have a Mastervolt intelligent three stage battery charger putting out 50amps at 12v. (I have a bigger charger sitting in the box. Installing it is on 'the list of things to do' but the 50amp will suffice for now).

I have a 660amp battery bank and 940watts of solar so I rarely use the generator but here are the stats that I came up with;

The manual for the genset states that diesel usage is .4 gph at maximum load with an average of .2 gph. The Mastervolt charger uses 825 VA at maximum draw which, if my math is correct is around 800 watts of energy. 800 watts is less than 1/4 of the maximum output of the generator. Therefore, I figure that the genset, if used just for charging, is consuming around 0.2 gph. So, how does that compare to my engine?

Turning off the generator, I turned on the port engine and played with the throttle until the alternator was also putting 50 amps back into the house bank via my Balmar charger. The rev counter showed that the engine was running fairly slowly at 1450 rpm. My Yanmar manual shows that the fuel consumption of the engine at 1450 rpm is .4 gph.

So in conclusion, running the genset compared to the engine uses roughly half the fuel in order to charge the batteries at the same rate. I imagine that once I fit the bigger charger, the advantage of the genset will increase exponentially. This is fairly imprecise and there are obvious pro's and con's to using either the genset or the engine but even given that they are estimates, given the choice, for me using the generator for charging is preferable.
__________________

__________________
Privilege is offline   Reply With Quote
Reply

Tags
battery, generator

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
Alternator only charges 'Start' battery not house bank. How to add them? SteelCruiser Electrical: Batteries, Generators & Solar 21 07-03-2016 16:47
Which Are the Faster Cantanas? canadian cat Multihull Sailboats 31 19-09-2012 19:33
New high tech battery that charges in one hour. mrlee Electrical: Batteries, Generators & Solar 5 21-04-2012 04:43
Cruising charges/cost questions kkugley General Sailing Forum 1 18-09-2008 19:58



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 03:07.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.