Cruisers Forum

Join CruisersForum Today

  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
Thread Tools Search this Thread Rate Thread Display Modes
Old 15-10-2014, 04:43   #1
Registered User

Join Date: Sep 2011
Location: Brisbane
Posts: 12
Send a message via Skype™ to howardyoube

I am about to change from an 1981 mono hull to a 2000 Cat. My question is this.

There seems to be mainly AC sockets and very few 12 volt DC outlets. I have lots of DC outlets on my boat now and tend to use these and not the inverter.
Is this "normal" or am I just old fashioned ? The Cat is an ex charter boat .

Does it make any difference to battery life and which is the best way to go?

Any sound practical advice would be appreciated

howardyoube is offline   Reply With Quote
Old 15-10-2014, 04:50   #2

Join Date: Jul 2007
Location: currently in Bahamas
Boat: Hunter 410
Posts: 16,293
Re: AC/DC ?

It doesn't make sense to use the inverter to power stuff if you could instead power it with DC because there is a power loss in the inverter.

But with that said my boat only currently has 1 DC outlet but has AC outlets in many places.

sailorboy1 is offline   Reply With Quote
Old 15-10-2014, 05:40   #3
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 12,132
Re: AC/DC ?

Just do the math and that will answer your question. Typically when running many AC devices these days you go thru a power supply too. Most of these are cheap and inefficient and many will draw power even if the device is disconnected from them. So you have loss thru the inverter (typically at least 5% even on a high end inverter...low end ones are worse) then additonal loss thru the power supply.

I ran the numbers on an inverter-power supply set up on my boat a few years ago and came up w a 30% loss for that installation! Way more efficient to go direct DC.

You can also get DC-DC power supplies for devices which take other than 12V. More efficient than inverting from DC-AC then back to DC thru a power supply. For example, many devices now take 5V as supplied over USB interfaces. I installed a 12V to multiport USB adaptor last season which we use a lot now to charge/run small electronics.

And my cat, also built in 2000, has a bunch of AC outlets (main salon, galley, and one in each cabin). They do come in handy for occassional use like running a power tool or a guest charging their cell phone, but for normal installed loads on the boat it is way more efficient to go direct DC.

I also control the inverter from the nav station. This way I can monitor power use...especially with guests aboard. I usually turn on when requested and then turn it off when they are done and/or before I go to bed.
belizesailor is online now   Reply With Quote
Old 15-10-2014, 05:59   #4
Moderator Emeritus
HappyMdRSailor's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: North Mississippi
Boat: 48 Wauquiez Pilot Saloon-C22 Chrysler Sunpiper- 19 Potter-Preparing to cruise w/my girl
Posts: 5,975
Re: AC/DC ?

You are a sailor...

And you bought a floating hotel room for tourists... Who don't tend to have a bunch of "sailor type 12v stuff" ...

Just throw in a bunch of DC outlets, and you'll have lots of extra convenient AC outlets!
In the harsh marine environment, something is always in need of repair...

Mai Tai's fix everything...
HappyMdRSailor is offline   Reply With Quote
Old 15-10-2014, 06:12   #5
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 30,045
Re: AC/DC ?

I think the lack of DC outlets speaks to the intended use of the boat and by whom.
Good news is DC outlets are easier to add than AC
a64pilot is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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

Advertise Here

All times are GMT -7. The time now is 13:44.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.