Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 05-09-2015, 16:12   #16
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 7,330
re: Use Main Engine as Generator-idling

Quote:
Originally Posted by Bill_E View Post
...
I agree with Stu, when my batteries are low, my Balmar generator must pull 5 hp off my 27 hp diesel. I can sure hear it load down!

Bill
Wow, that's impressive.
That must be well over 200 amps, what size is the Balmar and what size is the battery bank?
__________________

__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 05-09-2015, 16:58   #17
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 7,330
re: Use Main Engine as Generator-idling

Quote:
Originally Posted by DumnMad View Post
However a truck is only under full load going up hills - most of the time its on quite low load just trucking along.
Thread drift alert
I concur with high loads going up hills and add that high loads are experinced when accelerating.
However when "just trucking along" is more than just "quite low" IMHO. Any vehicle using pneumatic wheels is going "uphill" constantly.

Still you point is true, they use most power climbing hills.
__________________

__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 06-09-2015, 14:37   #18
Registered User

Join Date: Dec 2014
Location: the Med
Boat: Nauta 54' by Scott Kaufman/S&S - 1989
Posts: 1,059
Images: 3
re: Use Main Engine as Generator-idling

1. A generator has a 5-7 kw output, so it is much more than a charger! It runs the Double of any standard household power line....

2. A cold diesel, when idling, suffers from inertial forces which are higher than when going full throttle. Better to operate it a bit faster, it must sound rounded, not choppy!
__________________
TheThunderbird is offline   Reply With Quote
Old 07-09-2015, 10:08   #19
Registered User
 
BobH260's Avatar

Join Date: Aug 2009
Posts: 160
re: Use Main Engine as Generator-idling

I have solar (325W), a diesel generator (3.5 KW), and a 140 A alternator with Balmar ext reg. The house bank is 410 Ahrs AGMs. We live aboard about 5 months of the year. The solar can supply all our electrical needs if it is sunny.

I don't consider our alternator a waste of money. Our original stock alternator (50A) with internal regulator never put out more than 40 amps and would drop that down to 30 A quickly as it began to over heat, it could never fully charge the battery bank no matter how long I motored, the output voltage was just too low. Many of the stock alternators have this issue and is the reason many cruisers spend the money on a bigger alternator, ext. reg. rather than replace the batteries too often because they are always undercharged. The new alternator easily puts 100 amps into the batteries in bulk at only 1200 rpms. If we do have a deep discharge we can quickly complete our bulk charge and let the solar finish it off.

Our battery bank is almost always at 100% everyday. The right choice depends on where the boats is used and how it is used.

Bob
__________________
BobH260 is offline   Reply With Quote
Old 07-09-2015, 10:17   #20
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,342
Re: use main engine as generator-idling

Quote:
Originally Posted by stefano_ita View Post
Hi all

i was wondering, what if using the main engine as generator? i saw engine fitted with 2 or even 3 very big alternator to keep battery charged...

and if a smaller alternator is used, some one can please confirm me that diesel doesn't like idling for long time due the low oil pressure? excessive engine wearing and so on...

what would be acording to you a safe high idling speed? let's say 750-800 rpm normal idling...at least 1000-1100rpm would be enought?

thanks all
It's been a long disputed theory whether it's safe to run your diesel at lower rpms. Most of my boats have used the main engine for battery charging a lot. I've not had issues related to that. Truckers leave their engines idling all the time. Your engine is not just idling if it's also working. You can hear an alternator drag the engine rpm down when it's activated. I found that 1100-1200 rpms worked pretty well for charging. Often I would start higher for the 15-20 mins the alternator was putting out peak amperage.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 07-09-2015, 11:18   #21
Registered User
 
four winds's Avatar

Join Date: Oct 2010
Location: Wandering the US Gulf Coast
Boat: 78 Pearson323 Four Winds
Posts: 2,136
Re: Use Main Engine as Generator-idling

Allow me to add my experience.

Have been wandering about and at anchor for one year now. Maybe two nights in a marina during this past year. And loving it, too.

Yanmar (3gm30f-2500hrs.) with new Hitachi 80 amp alternator. Two new, a year ago, group 31 Deca/East Penn Batteries, 220ah total. No solar, no genset.

Typical 12v loads, lights with some led some not yet, vhf, AP, chartplotter, stereo. Plus a nice 36" flatscreen, small efficient dorm fridge, laptop, smartphone running off a 1k watt pure sine inverter.

I knew I'd kill the batts in a year but have been hoping to add solar and switch to 440ah gc2 flooded by now. Hasn't happened yet.

Batteries haven't been back to 100% the whole year except the two times in the marina. I sail exclusively for fun and financial reasons and only motor when needed. In a year I've almost never motored more than a couple hours at a time. The couple times I motored more had no noticable benefit to the batts state of charge.

The first six months I could use the fridge and tv. Now my capacity is dimished to the extent that those two loads are no longer used. Sure miss a nice cold drink and a little tv everyday.

Only a volt meter for monitoring but my guess is I'm working between 50% to 70% SOC on the batts.

Running the engine at anchor (1400-1600rpm) to charge effects my engine, no doubt. If I stay in the same place a few days, running the engine morning and evening, gets me by. But I struggle to keep the voltage above 12.2v.

And my cylinders glaze over. When I weigh anchor and move on I get oil smoke for a while. More revs, more smoke. So I keep the revs to 1800-2000 for the first hour or so, maybe motorsail. After 1-2 hours the rings are seated again and full power load causes no smoke.

Expected all of this would happen because of my online education in the cruising life from reading CF daily for the last seven years or so.

Not a checkbook sailor, so improvements to my circumstances are slow to occur.

That's my experience, honestly presented.
__________________
Life begins at the waters edge.
four winds is offline   Reply With Quote
Old 07-09-2015, 16:17   #22
Registered User
 
DumnMad's Avatar

Join Date: Mar 2012
Location: Nelson NZ; boat in Brisbane
Boat: 45ft Ketch
Posts: 1,246
Re: Use Main Engine as Generator-idling

Quote:
Originally Posted by four winds View Post
And my cylinders glaze over. When I weigh anchor and move on I get oil smoke for a while. More revs, more smoke. So I keep the revs to 1800-2000 for the first hour or so, maybe motorsail. After 1-2 hours the rings are seated again and full power load causes no smoke.
Sounds like good management but not sure you should call that glazed over yet, more like its dirty and you are preventing it from being glazed over.

Nigel Calder says "If black smoke persists once an engine is up to speed, the engine is crying out for attention...............If the engine is not overloaded and the airflow is unobstructed, poor injection is the number one suspect for black smoke."
__________________
DumnMad is offline   Reply With Quote
Old 07-09-2015, 16:55   #23
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 7,330
Re: Use Main Engine as Generator-idling

Quote:
Originally Posted by four winds View Post
Allow me to add my experience......

Running the engine at anchor (1400-1600rpm) to charge effects my engine, no doubt. If I stay in the same place a few days, running the engine morning and evening, gets me by. But I struggle to keep the voltage above 12.2v.

And my cylinders glaze over. When I weigh anchor and move on I get oil smoke for a while. More revs, more smoke. So I keep the revs to 1800-2000 for the first hour or so, maybe motorsail. After 1-2 hours the rings are seated again.....

That's my experience, honestly presented.
If I may suggest a possible improvement...

I pop the engine into reverse when charging at anchor (or mooring); still operate around 1,500 rpm but this way you will have additional load on the engine.

Also 2,000 is still pretty lightly loaded for a 3GM30F. Assuming you are correctly proped and have a clean hull, you should be able to get 3,400 to 3,600 at WOT. Your Yanmar engine manual will advise you to run at WOT for 10 minutes after every 2 hours of lightly loaded use in order to clear the clyinders etc.

Even if you have reasons not to go to say 3,500, go at least to say 2,800 or 3,000.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 08-09-2015, 00:43   #24
Registered User
 
four winds's Avatar

Join Date: Oct 2010
Location: Wandering the US Gulf Coast
Boat: 78 Pearson323 Four Winds
Posts: 2,136
Re: Use Main Engine as Generator-idling

Hey DumnMad, Wotname, thanks for the feedback. Very much appreciated.

The smoking is blue oil smoke not black fuel smoke. I have been assuming that is oil getting past the rings until they reseat. There is slight oil loss over time as well.

Been hanging out in Gulport, Florida for a couple months now. About to head on towards the Keys if I can ever get a favorable wind and not constant daily tstorms. But since I have been going to the city dock here to shop or eat I have used that opportunity to charge up in gear for load while tied up.

I have occasionally used reverse at anchor as well but less comfortable doing so than may be necessary as I do trust my ground tackle. Puts my bow off the wind and I lose airflow through the boat, too. Maybe I should use reverse always.

I get 3200 WOT no load and 3000rpm WOT under load. I know the tachs can sometimes be off some good bit. Could be overpropped a little. But I suspect a valve lash adjustment could help here. It's overdue. I have an ear for engines from doing my own mechanic work since a kid and can hear the tappets talking to me faintly through the diesel noise.

Only time I've had black smoke is when the prop was ridiculously fouled from neglect. Living at a marina and regularly day sailing. Just using the engine to exit or enter marina. Low fouling area so only cleaned twice a year. When I went back on the hook last year started using the engine more and could only get 2200rpm chugging black smoke. I had no idea since I used the engine lightly for ten minutes each day sail and blew it out in neutral occasionally. Was hauling out for bottom work before my current coastal cruising anyway and took care of it.

One day I'll have solar and can be more kind to my engine. For now trying to use best practices from the past.
__________________
Life begins at the waters edge.
four winds is offline   Reply With Quote
Old 09-09-2015, 03:38   #25
Registered User

Join Date: Jun 2015
Posts: 462
Re: Use Main Engine as Generator-idling

thanks all

i would need a 4-5 kw generator to keep charged a 24 (or maybe 48 v)battery bank for house load...
live aboard trawler with air conditioning and so on...4 kw solar panel and about 70kwh of storage...want it water cooled to use it to warm the boat during winter via a heat exchanger...but the smallest water cooled genset is 15-20 kw... and 15.000 usd..no needed, having 2 engine i guess to have enough reliability to use one by one as generator in case the battery gets lower..

maybe i should open a new 3d explaining all the project any ideas on wich area should i open it?

thankss
__________________
stefano_ita is offline   Reply With Quote
Old 09-09-2015, 16:43   #26
Registered User
 
Ericson38's Avatar

Join Date: Aug 2012
Location: Virginia
Boat: Taswell 49 Cutter
Posts: 187
Re: Use Main Engine as Generator-idling

Quote:
Originally Posted by stefano_ita View Post
Hi all

i was wondering, what if using the main engine as generator? i saw engine fitted with 2 or even 3 very big alternator to keep battery charged...

and if a smaller alternator is used, some one can please confirm me that diesel doesn't like idling for long time due the low oil pressure? excessive engine wearing and so on...

what would be acording to you a safe high idling speed? let's say 750-800 rpm normal idling...at least 1000-1100rpm would be enought?

thanks all
I have heard that it depends on the engine manufacturer's recommedations too, on side loads on the front pulley. By the time the dual grove pulley is installed, there is quite a lever arm between the belt force and the front main bearing, so you need to evaulate just how much power is going to be pulled from the front end. One alternator each side would counteract the side loads to some degree. If the engine is going to work under load, it needs some rpm to keep oil pressure up and trade torque (force on rod bearings) for rpm to get to the same hp that the alternators require. Then you can size the diameters of the engine pulley versus the alternator pulley so that the engine rpm can be reached. Same issues on the alternator side, with rotor speeds required, and the fans that cool the rotor/field windings.

The engine room is going to get hot, since power conversion is air cooled now, versus an AC generator which is going to throw the heat out the water cooled exhaust. Big blowers would help keep things from drying out down there.
__________________
Ericson38 is offline   Reply With Quote
Old 10-09-2015, 06:31   #27
Registered User
 
Privilege's Avatar

Join Date: Oct 2009
Location: Bermuda
Boat: Privilege 435
Posts: 362
Images: 12
Re: Use Main Engine as Generator-idling

I recently did some comparison calculations on this subject so thought I'd share with the group.

I have twin Yanmar 4JH3. 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 diesel generator putting out 3.5kw 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, which 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 get a 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, using the generator for charging is preferable.

__________________
Privilege is offline   Reply With Quote
Old 10-09-2015, 06:54   #28
Registered User
 
BobH260's Avatar

Join Date: Aug 2009
Posts: 160
Re: Use Main Engine as Generator-idling

Nigel Calder does a good analysis of the true cost of generating electricity with your engine or generator. It makes solar look like a no brainer !

The cost of energy on boats - Ocean Navigator - March/April 2012

Bob
__________________
BobH260 is offline   Reply With Quote
Old 10-09-2015, 15:46   #29
Registered User
 
DumnMad's Avatar

Join Date: Mar 2012
Location: Nelson NZ; boat in Brisbane
Boat: 45ft Ketch
Posts: 1,246
Re: Use Main Engine as Generator-idling

Privilege & BobH260. Thanks, good info.
__________________
DumnMad is offline   Reply With Quote
Old 11-09-2015, 10:32   #30
Registered User

Join Date: Jun 2015
Posts: 462
Re: Use Main Engine as Generator-idling

thanks all for the answer

a question...if i get 2 24v alternator in serie do i get 48 v dc alternator? with diode for stabilize the current
__________________

__________________
stefano_ita is offline   Reply With Quote
Reply

Tags
engine, 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
Problem with New Motor Idling Target9000 Engines and Propulsion Systems 8 12-10-2011 17:34
Displayed Engine Hours and Idling sailorboy1 Engines and Propulsion Systems 10 26-03-2010 15:15
2GM20F Idling / Charging / Fuel Consumption cfoxcvg Engines and Propulsion Systems 8 27-02-2010 05:46
Idling Too Long? unbusted67 Engines and Propulsion Systems 56 04-06-2009 16:56
Is idling an outboard for long periods bad for it? PatrickS Engines and Propulsion Systems 4 16-02-2009 07:58



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:29.


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.