Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 12-08-2010, 07:11   #1
Registered User

Join Date: Aug 2008
Location: Coastal VA
Posts: 130
Calculate Amp Hours From Reserve Capacity ?

Searching, I found two references on how to calculate average amp-hours using reserve capacity.

Amp/Hours = 0.6 * reserve capacity

Amp/Hours = (Reserve Capacity / 2) plus 16

With two Exide 4D deep cycles rated at 320 RC each, one method gives 384 AH and the other 336 AH, for both batteries combined.

This is a 12% to 14% difference. Which formula might be more accurate? The second adds 16. That would make lots of variation in the AH/RC for a small vs a larger system, and that doesn't seem right to me.

Also, I guess in actual application there could be many other factors that will make a 12% initial accuracy difference not much to consider...

"In theory there is no difference between practice and theory. In practice there is."
- Yogi Berra

Any observations or input appreciated.

Whimsy is offline   Reply With Quote
Old 12-08-2010, 07:35   #2
Marine Service Provider
Maine Sail's Avatar

Join Date: Jan 2007
Location: Maine
Boat: CS-36T - Cupecoy
Posts: 2,868
An Exide Nautilus 4D is rated at 160 ah so neither may be right. those calcs are ball park only in my experience. The only way to really know is to physically test it.

To see what i mean do the calcs on ten different batts with published rc & ah/20 hr rates..

Marine How To Articles
Maine Sail is online now   Reply With Quote
Old 12-08-2010, 08:31   #3
Moderator Emeritus
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 29,347
Images: 240
Peukert's law won't permit Amp-Hour Capacity (20 hr rate) and Reserve Capacity to be exactly correlated.
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

GordMay is offline   Reply With Quote
Old 12-08-2010, 09:01   #4
Registered User

Join Date: Aug 2008
Location: Coastal VA
Posts: 130
Whimsy is offline   Reply With Quote

Thread Tools
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

Similar Threads
Thread Thread Starter Forum Replies Last Post
How to Convert to Amp Hours? fullkeel2 Electrical: Batteries, Generators & Solar 5 03-01-2010 01:08
Battery Capacity - Reserve kcmarcet Electrical: Batteries, Generators & Solar 11 20-10-2009 11:02
Charging Capacity & Time to Recharge BlueSovereign Electrical: Batteries, Generators & Solar 12 05-05-2009 19:06
How Many Amp Hours? ssullivan Electrical: Batteries, Generators & Solar 15 10-10-2005 19:25

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:22.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.