Is a little Generator worth it? - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Chat  
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
 Not a Member? 
  #1  
Old 02-09-2010
Member
 
Join Date: Jan 2002
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
akin_alan is on a distinguished road
Is a little Generator worth it?

I have a Tohatsu 9.8 outboard on my 30' 1974 Grampian sloop that I bought a few months ago. Very much enjoying the boat. My understanding is that the outboard charges the battery with 7 amps DC power.
I read the specs on Yamaha and Honda Generators. They put out a whopping 1000 Watts AC power! Well AC is something that I don't use much on my boat. DC is what I need. They only generate 7-8 amps DC power. 8amps x 12 volts = 96 watts DC.... I think that ain't much. I got three 90 (+-) amp batteries. Does that mean I got to run this generator for nearly 30 hours just to charge the batteries?
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 02-09-2010
Mechsmith
 
Join Date: Jun 2009
Location: Almost Heaven West Virginia
Posts: 215
Thanks: 1
Thanked 15 Times in 14 Posts
Rep Power: 6
Mechsmith is on a distinguished road
I have only a 6 amp alternator on the outboard, but I also carry a 12V-35 amp gasoline powered portable just in case. You could also run a battery charger off one of the little 120 V chargers. Not efficient but it beats rowing.

The six amps has so far been enough if I start with fully charged batteries.

I use a battery isolator switch wired so that if I kill the one house battery. (Fall asleep while reading for instance) the other battery will still start the motor. Also I minimize my electricity use with a solar powered masthead anchor light.

LED running lights are on my wish list.
Reply With Quote Quick reply to this message Share with Facebook
  #3  
Old 02-09-2010
whroeder's Avatar
Member
 
Join Date: Aug 2007
Location: Palm Bay, FL
Posts: 87
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
whroeder is on a distinguished road
Quote:
Originally Posted by akin_alan View Post
Does that mean I got to run this generator for nearly 30 hours just to charge the batteries?
Charging rate drops off as they charge. That, plus you won't get that peak charging rate, means it will take more than twice that long.
Reply With Quote Quick reply to this message Share with Facebook
  #4  
Old 02-09-2010
Senior Member
 
Join Date: Jul 2001
Posts: 1,174
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 14
k1vsk will become famous soon enough
Not enough info to make an intelligent conclusion. You need to tell us how much power you have onboard (what is the cap of your battery bank?), how much power to typically draw from that bank, how long do you typically go without a full recharge, etc.
Buying a good (i.e., Honda) generator can be a great addition but it's impossible to advise without the above info to know if you need it.
Reply With Quote Quick reply to this message Share with Facebook
  #5  
Old 02-09-2010
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,290
Thanks: 0
Thanked 14 Times in 12 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
I'd point out that the Tohatsu is only going to give you 7 amps when it is running full out... usually it will give less than 2-3 amps.

The small gasoline generators aren't really good for charging the batteries on a boat, since they have relatively low output. Using the AC side would make more sense, since you can run a fairly beefy AC battery charger with 1000 watts... one that puts out over 40 amps @ 14.4 VDC pretty easily.

If you have AGM batteries, then this might make sense, since you could get them back up to 80-85% of charge level relatively quickly. But, with wet cells, with their more limited current acceptance rates, charging them to the 80-85% level will take more time...

IMHO, you'd be better off, if you only use the boat on weekends or occasionally, rather than living aboard, to get a medium size solar panel to recharge the batteries. I've written a basic primer for solar power on boats which you can read here.

Quote:
Originally Posted by akin_alan View Post
I have a Tohatsu 9.8 outboard on my 30' 1974 Grampian sloop that I bought a few months ago. Very much enjoying the boat. My understanding is that the outboard charges the battery with 7 amps DC power.
I read the specs on Yamaha and Honda Generators. They put out a whopping 1000 Watts AC power! Well AC is something that I don't use much on my boat. DC is what I need. They only generate 7-8 amps DC power. 8amps x 12 volts = 96 watts DC.... I think that ain't much. I got three 90 (+-) amp batteries. Does that mean I got to run this generator for nearly 30 hours just to charge the batteries?
__________________
Sailingdog

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

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Quick reply to this message Share with Facebook
  #6  
Old 02-09-2010
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,356
Thanks: 0
Thanked 86 Times in 77 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
As stated above you could use the generator to power an ac charger. Best to keep the charger to about 35% of the generators output for the most efficient charging though. Some chargers don't get along that well with the waveform produced by many generators and will produce a lower amperage when the generator is producing near its max output.

But why go sailing to listen to a generator if you don't have to. With LED lighting and careful management, especially if you don't have any refrigeration or electronics like radar using power, a solar panel or two as mentioned above can supply all you need.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Quick reply to this message Share with Facebook
  #7  
Old 02-09-2010
Senior Member
 
Join Date: Mar 2008
Posts: 536
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Architeuthis is on a distinguished road
Quote:
Originally Posted by mitiempo View Post
But why go sailing to listen to a generator if you don't have to. With LED lighting and careful management, especially if you don't have any refrigeration or electronics like radar using power, a solar panel or two as mentioned above can supply all you need.
Dad? LOL just kidding but I know the argument well.

Seriously you do not need the LED lighting. My Dad did the loop from Thunder Bay to Cuba with only a couple of very old cheap wet cell batteries. It can be done.

If you get rid of all the stuff that uses electricity, even oil lamps can be used for navigation, not only will it be cheaper but it is much more like "real" sailing.

Of course to be a real sailor you have to get rid of that engine and be towed into harbours, with a row boat I assume, just like the old days.

So for some, no generator, no engine, for others they wouldn't be on the water without one.
__________________
Have faith that the oceans are going to rise and flood the world, that plague and pestilence brought on by Climate Change is going to punish us for not believing. Please do as they say it is our only hope. :P
Reply With Quote Quick reply to this message Share with Facebook
  #8  
Old 02-09-2010
jaschrumpf's Avatar
1975 Newport 28
 
Join Date: Jun 2002
Location: Monrovia, MD
Posts: 573
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 13
jaschrumpf is on a distinguished road
Quote:
Originally Posted by akin_alan View Post
I have a Tohatsu 9.8 outboard on my 30' 1974 Grampian sloop that I bought a few months ago. Very much enjoying the boat. My understanding is that the outboard charges the battery with 7 amps DC power.
I read the specs on Yamaha and Honda Generators. They put out a whopping 1000 Watts AC power! Well AC is something that I don't use much on my boat. DC is what I need. They only generate 7-8 amps DC power. 8amps x 12 volts = 96 watts DC.... I think that ain't much. I got three 90 (+-) amp batteries. Does that mean I got to run this generator for nearly 30 hours just to charge the batteries?
I'm a bit confused with the power conversion. A Honda 1000W generator puts out 1000W at 120V AC. 1W = 1A X 1V, so in this case:

1000W = ~8A X 120V

If you replace that 120V with 12V and keep the wattage the same, don't you get:

1000W = ~80A X 12V

The power output is the wattage, and it should remain constant, shouldn't it? If you lower the voltage, doesn't the amperage increase? Or is this one of those AC/DC things?
__________________
S/V Free Spirit

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

Monrovia, MD
Reply With Quote Quick reply to this message Share with Facebook
  #9  
Old 02-09-2010
Senior Member
 
Join Date: Mar 2008
Posts: 536
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Architeuthis is on a distinguished road
You are correct 1000w is 8amp at 120v and 80 at 12v.

With AC it is better to use KVA to avoid the confusion. To get Watts in an AC circuit you need to know the Power Factor (PF) but lots of us just us Watts which means we are using a PF of 1 which doesn't really happen in real life but close enough.

In other words I understood the OP was referring to the DC winding that comes with many generators which is limited to about 8 amps at 12volts, and as pointed out rarely gives you even that.
__________________
Have faith that the oceans are going to rise and flood the world, that plague and pestilence brought on by Climate Change is going to punish us for not believing. Please do as they say it is our only hope. :P
Reply With Quote Quick reply to this message Share with Facebook
  #10  
Old 02-09-2010
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,356
Thanks: 0
Thanked 86 Times in 77 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
A lot of generators like the Honda have separate DC outputs and this not a very high amp output. These DC outputs cannot be used simultaneously with the AC outputs.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

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:

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

 
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



All times are GMT -4. The time now is 05:22 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, 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.