How common are DC Generators? - SailNet Community
Reply
 
LinkBack Thread Tools
post #1 of 13 Old 10-01-2011 Thread Starter
Member
 
Join Date: Mar 2010
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
 
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.
Bowedtoothdoc is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 13 Old 10-01-2011
Senior Member
 
Zanshin's Avatar
 
Join Date: Aug 2006
Location: Germany
Posts: 2,297
Thanks: 0
Thanked 29 Times in 27 Posts
Rep Power: 9
 
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.
Zanshin is offline  
Quote Quick Reply Share with Facebook
post #3 of 13 Old 10-01-2011
the pointy end is the bow
 
erps's Avatar
 
Join Date: Aug 2006
Location: La Conner, Washington
Posts: 6,260
Thanks: 2
Thanked 27 Times in 26 Posts
Rep Power: 10
   
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.
erps is offline  
Quote Quick Reply Share with Facebook
post #4 of 13 Old 10-01-2011
Senior Member
 
mitiempo's Avatar
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,487
Thanks: 0
Thanked 94 Times in 85 Posts
Rep Power: 8
   
Bowed

Can you be more specific? Do you have a link?

Brian
Living aboard in Victoria Harbour
mitiempo is offline  
Quote Quick Reply Share with Facebook
post #5 of 13 Old 10-01-2011 Thread Starter
Member
 
Join Date: Mar 2010
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
 
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.
Bowedtoothdoc is offline  
Quote Quick Reply Share with Facebook
post #6 of 13 Old 10-01-2011
Senior Member
 
mitiempo's Avatar
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,487
Thanks: 0
Thanked 94 Times in 85 Posts
Rep Power: 8
   
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
mitiempo is offline  
Quote Quick Reply Share with Facebook
post #7 of 13 Old 10-01-2011
Member
 
Join Date: Mar 2011
Posts: 88
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 5
 
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.
VetMike is offline  
Quote Quick Reply Share with Facebook
post #8 of 13 Old 10-02-2011
Senior Member
 
Zanshin's Avatar
 
Join Date: Aug 2006
Location: Germany
Posts: 2,297
Thanks: 0
Thanked 29 Times in 27 Posts
Rep Power: 9
 
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.
Zanshin is offline  
Quote Quick Reply Share with Facebook
post #9 of 13 Old 10-02-2011 Thread Starter
Member
 
Join Date: Mar 2010
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
 
I think the listing has a misprint, and they meant that the yacht has an additional 12v Balmar alternator.
Bowedtoothdoc is offline  
Quote Quick Reply Share with Facebook
post #10 of 13 Old 10-02-2011
Senior Member
 
mitiempo's Avatar
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,487
Thanks: 0
Thanked 94 Times in 85 Posts
Rep Power: 8
   
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
mitiempo is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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

Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome