Battery Shopping and Capacity Confusion - Page 2 - 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? 
  #11  
Old 09-05-2011
Stu Jackson's Avatar
Senior Member
 
Join Date: Jul 2001
Posts: 810
Thanks: 0
Thanked 9 Times in 8 Posts
Rep Power: 14
Stu Jackson is on a distinguished road
PorFin's right.

Even with 4 or 5 Group 24 batteries in your new house bank, you'll be just fine for a weekend with a fridge running. 5 x 60 ah each = 300 ah, 50% usable, 150 ah. You could turn the fridge off at night when no one's using it.

Here's an example:

Reply #9 "Breaking In" New Wet Cell Batteries

Understanding the difference between (instantaneous) amps and amp hours is critical to understanding electrical systems, so do some reading up.

We have a Link 2000 also, and it's a great tool. As eith all tools, when used correctly...

Good luck.
__________________
Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
Reply With Quote Quick reply to this message Share with Facebook
  #12  
Old 09-05-2011
hellosailor's Avatar
Senior Member
 
Join Date: Apr 2006
Posts: 10,875
Thanks: 2
Thanked 101 Times in 98 Posts
Rep Power: 10
hellosailor has a spectacular aura about hellosailor has a spectacular aura about
You may find a 10% variation in the rating of different "Group24" or other same-size-group batteries depending on the maker. But think carefully about Optima! They are ROUND AGM cells, combined in a RECTANGULAR case. That means they lose about 10% of the possible volume in that case, so they lose 10% capacity compared to flat-plate AGM batteries in the same size group. they are also about 50% more expensive than flat-plate AGM batteries, even though spiral construction is supposed to be both stronger AND cheaper.
Optima? Not for me, no thanks, not at that price with reduced capacity to boot.

I'd also suggest measuring your battery spaces carefully, there are some slightly different sizes (like Group31) that may be an inch higher or wider or otherwise "close" that can again push your capacity 10-20% higher without getting into batteries that are too big for one person to handle.
Reply With Quote Quick reply to this message Share with Facebook
  #13  
Old 09-05-2011
Junior Member
 
Join Date: Aug 2011
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
visi0n is on a distinguished road
Batteries and capacity

All great information, especially the books -- good stuff. Wish I had them about $1k ago

I'm aware, of course that my radar won't always be running, nor will the vhf when I'm at anchor. But, I do see those amp hours being gobbled up readily by the kids watching a dvd before bed in the event we're under storm and not on the beachside camping.

I'm basing the load conditions off of a online calculator more than observation on my link, since I'm using far more busy sailing than playing with electronics in practicality. I'm thinking the TV use at anchor is really what's pushing me past the limit. Maybe time to just bring a 4 or 5 hour portable and not chew down my boat's bank.

this calculator:
Marine & RV Battery Load Calculator

I've seriously considered these Duracell's I've seen at Sams. They are only $100, which kind of concerns me. ;/ Looks like I have some reading to do..

Last edited by visi0n; 09-05-2011 at 07:09 PM.
Reply With Quote Quick reply to this message Share with Facebook
  #14  
Old 09-06-2011
Junior Member
 
Join Date: Aug 2011
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
visi0n is on a distinguished road
Thanks all for the help..

Thanks all, for the help.. Glad I asked.

I sort of ran out of money for this project until some of my customers settle their debts, so I'm part of the way there..
Got the batteries from Sams, hopefully they'll hold up.

I put two Duracell AGM Golf Cart (200 ah) batteries in series on the house side. (I have just enough room for two more in the coming weeks, for a series/parallel wiring)

and two Duracell 12v 55ah Marine AGM's in parallel on the alternator for starting.. Why two? Well, I'm a little nervous about a failure in the series and somehow being down to a useless 6v leg, so I see the second 12v AGM as a hot-standby that could be readily re-wired or switched, at least until I can complete the houe bank in the coming weeks..

As it stands, it gives me 200 ah rated bank on the house for now and room to add two more identicals and push up to 400 in the coming weeks when I'm feeling froggy...

Thanks again for the suggestions, Sams prices were really pretty reasonable, especially compared to West Marine and the Auto parts dealers. Hopefully the reasonable price doesn't bite me.
Reply With Quote Quick reply to this message Share with Facebook
  #15  
Old 09-07-2011
Stu Jackson's Avatar
Senior Member
 
Join Date: Jul 2001
Posts: 810
Thanks: 0
Thanked 9 Times in 8 Posts
Rep Power: 14
Stu Jackson is on a distinguished road
Why not use one of the 12V for the reserve bank and combine the 2 6V and the other 12V. Your house bank will be bigger and better and last longer. Perhaps you're missing the points mentioned in this entire topic.
__________________
Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
Reply With Quote Quick reply to this message Share with Facebook
  #16  
Old 09-08-2011
Junior Member
 
Join Date: Aug 2011
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
visi0n is on a distinguished road
The 6V serial have different capacities and charge/discharge characteristics than the 12volt.

My charger manual warns against charging disparate batteries amongst a shared bank. Even though they share chemistry commonalities, they are very different in discharge rate, etc.

The 12 volt AGMs are only 55 ah, anyway. It's a higher crank amp, lower capacity battery. I wouldn't want to risk nuking my charger, negating it's safety algorithm or grenading my batteries for a measly 55 amp hour, at this point.

Last edited by visi0n; 09-08-2011 at 11:55 AM.
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery Confusion - Amp Hours vs. Reserve Capacity Maine Sail Electrical Systems 11 04-05-2011 03:14 PM
Group 31 Battery Capacity lbdavis Gear & Maintenance 39 04-08-2008 07:22 AM
Battery switch confusion... advice jg91604 Beneteau 1 02-26-2008 08:03 PM
How much battery power / capacity Petar Gear & Maintenance 3 02-18-2008 05:26 PM
House battery capacity wwilson Gear & Maintenance 7 03-07-2001 09:06 PM


All times are GMT -4. The time now is 02:05 PM.

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.