How common are DC Generators? - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
 Not a Member? 
  #1  
Old 10-01-2011
Member
 
Join Date: Mar 2010
Posts: 65
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
Bowedtoothdoc is on a distinguished road
How common are DC Generators?

I came across a boat on yachtworld that I am very interested in. After closely looking at the specs I discovered that the boat has a DC generator and I am pretty sure it came that way from the factory. Being in the south I am not sure what the uses of a DC generator would be other than charging the battery's. The boat also has a 2500 watt inverter that I would imagine could run allot of AC appliances short of AC. How common are DC generators and why? Also the boat does not have AC, can an 5000 watt inverter run AC or would I need to get a new genset?

Last edited by Bowedtoothdoc; 10-01-2011 at 09:26 AM.
Reply With Quote Share with Facebook
  #2  
Old 10-01-2011
Zanshin's Avatar
Senior Member
 
Join Date: Aug 2006
Location: Germany
Posts: 2,165
Thanks: 0
Thanked 14 Times in 14 Posts
Rep Power: 9
Zanshin is on a distinguished road
DC generators are not yet common. The main advantage of the DC generator is that the diesel engine can run at more efficient and different speeds than an AC generator. The AC models need to run with an RPM that is divisible by 60 or 50 in order to generate 60Hz or 50Hz for alternating current (typically 1500/3000RPM or 1600/3200RPM for slow or fast gensets and for 50Hz and 60Hz. With DC the generator doesen't need to run at any specific speed and thus can run more efficiently.
With progress in battery technology, specifically Lithium, the weight of batteries has gone down while the capacity and in particular the charging amperages have gone up and soon DC generators might come into their own; Fischer Panda has a hybrid ship which uses the DC genset for propulsion as well as for supplying the onboard electrical system.
Several months ago when I was deciding which sailboat to get, I mapped out a similar hybrid electrical propulsion using a DC generator ans would have opted for such a system had lithium batteries not had a price tag per KwH that was 10x higher than for lead-acid.

How many Kilowatts does your DC genset put out? It should be sufficient to run an air conditioning unit through the battery bank (used as a storage buffer) and a large inverter. Remember that the manufacturer ratings are optimistic at best and that inverter performance degrades quickly with higher temperatures and a 5000W inverter might lose 15%-20% and thus only deliver just over 4000W.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #3  
Old 10-01-2011
erps's Avatar
the pointy end is the bow
 
Join Date: Aug 2006
Location: La Conner, Washington
Posts: 6,154
Thanks: 2
Thanked 26 Times in 26 Posts
Rep Power: 10
erps will become famous soon enough erps will become famous soon enough
Quote:
I discovered that the boat has a DC generator and I am pretty sure it came that way from the factory.
Are you talking about a separate stand alone generator, or the belt driven generator on the ship's engine? Old cars and tractors had DC generators on them and they were replaced with alternators, which got more power at lower RPM.s

Quote:
Also the boat does not have AC, can an 5000 watt inverter run AC or would I need to get a new genset?
I can't imagine a battery bank large enough to be able to power a 5K inverter that would run AC. 5000 watts requires around 400 amps of battery power.
__________________
Ray
S.V. Nikko
1983 Fraser 41
La Conner, WA


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


Boating for over 25 years, some of them successfully.
Reply With Quote Share with Facebook
  #4  
Old 10-01-2011
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,114
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
Bowed

Can you be more specific? Do you have a link?
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
  #5  
Old 10-01-2011
Member
 
Join Date: Mar 2010
Posts: 65
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
Bowedtoothdoc is on a distinguished road
It's the Freedom 45 listed here: http://www.yachtworld.com/core/listi...g_id=1712&url=
Apparently has a separate 12V Balmar generator? I think they meant a 12 volt Balmar Alternator.

Last edited by Bowedtoothdoc; 10-01-2011 at 01:52 PM.
Reply With Quote Share with Facebook
  #6  
Old 10-01-2011
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,114
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
It may be the Ample Power Genie shown here Genie Diesel Alternators

Basically a small diesel with a large alternator as it is more efficient than running the larger main engine at a low load to charge batteries.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
  #7  
Old 10-01-2011
Member
 
Join Date: Mar 2011
Posts: 88
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 4
VetMike is on a distinguished road
Several months ago I was thinking about building a diesel generator using an old diesel engine and a generator but couldn't find a small diesel motor. I then found an article in either This Old Boat or a similar magazine with an article about building a diesel genset. I'll try to find the article and post it.
Reply With Quote Share with Facebook
  #8  
Old 10-02-2011
Zanshin's Avatar
Senior Member
 
Join Date: Aug 2006
Location: Germany
Posts: 2,165
Thanks: 0
Thanked 14 Times in 14 Posts
Rep Power: 9
Zanshin is on a distinguished road
Quote:
Originally Posted by erps View Post
...I can't imagine a battery bank large enough to be able to power a 5K inverter that would run AC. 5000 watts requires around 400 amps of battery power.
Well, I have 1200Ah @ 12V (600Ah @ 24V) aboard my new boat and a Victron 5000W inverter which could run AC, were I of a mind to do so. But the original poster didn't want to run the AC off the stored energy in the batteries, just charge the batteries from the DC genset while running the AC, in which case the capacity of the battery bank isn't that important.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #9  
Old 10-02-2011
Member
 
Join Date: Mar 2010
Posts: 65
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
Bowedtoothdoc is on a distinguished road
I think the listing has a misprint, and they meant that the yacht has an additional 12v Balmar alternator.
Reply With Quote Share with Facebook
  #10  
Old 10-02-2011
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,114
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
May be a misprint but DC generators are quite common and the most efficient way to charge the batteries. Beats running the main engine or having a big generator for AC. A DC generator and an inverter, which you will probably have anyway, is a lighter, lower maintenance solution. On a larger boat, say above 40', I would want one.

I have seen several, one on a 35' catamaran and one on a Saga 43 for example.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Common formulas and rules Sailinsolo Learning to Sail 18 11-21-2011 10:17 AM
Rally Fees Common? BJSoCal General Discussion (sailing related) 1 07-28-2010 01:20 PM
A more common diesel... mrhoneydew Gear & Maintenance 20 08-06-2008 08:44 AM
Common Knots and usage Brezzin Learning to Sail 20 12-21-2007 05:20 PM


All times are GMT -4. The time now is 12:32 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.