Measuring Battery Voltage - 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? 
  #1  
Old 11-10-2010
Senior Member
 
Join Date: Jul 2006
Location: Corpus Christi, Tx
Posts: 1,045
Thanks: 18
Thanked 21 Times in 20 Posts
Rep Power: 9
ccriders is on a distinguished road
Measuring Battery Voltage

I have a two prong outlet in the companionway near the DC panel. If I measure the battery voltage at this point with a digital multimeter, how accurate of a reading can I expect?
John
Reply With Quote Share with Facebook
  #2  
Old 11-10-2010
Maine Sail's Avatar
Senior Member
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 5,361
Thanks: 11
Thanked 122 Times in 90 Posts
Rep Power: 15
Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice
Quote:
Originally Posted by ccriders View Post
I have a two prong outlet in the companionway near the DC panel. If I measure the battery voltage at this point with a digital multimeter, how accurate of a reading can I expect?
John
What are you trying to determine with this reading?
__________________
______
-Maine Sail / CS-36T


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




© Images In Posts Property of Compass Marine Inc.


Reply With Quote Share with Facebook
  #3  
Old 11-10-2010
peikenberry's Avatar
Senior Member
 
Join Date: Apr 2000
Location: Seattle/Tacoma
Posts: 188
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 15
peikenberry is on a distinguished road
The most accurate is at the battery
__________________
Ike
My Boat building Web Site

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

My Boating Safety Blog

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

Dont Tell Me that I can't. Tell me how I can!
Reply With Quote Share with Facebook
  #4  
Old 11-10-2010
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,121
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
Very accurate for that point in the system. As posted the battery is the best place for voltage measurement and a voltmeter is usually wired direct to the battery. When nothing else is drawing power they should be close, the battery voltage a bit higher. If there is a large difference there is too much resistance somewhere from corrosion or an otherwise bad connection. Measuring voltage occasionally at different places on the boat can sometimes show problems you didn't know existed.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
  #5  
Old 11-11-2010
Senior Member
 
Join Date: Jan 2010
Location: Boston, MA
Posts: 523
Thanks: 2
Thanked 1 Time in 1 Post
Rep Power: 5
rmeador is on a distinguished road
If there is no load on this DC outlet, it should be a very accurate representation of the battery voltage. The voltmeter barely draws any current, so the voltage drop through the wires to the outlet will be negligible. If you're measuring it while it's under load, all bets are off.
__________________
1979 Gulfstar 37 Laissez Faire
Reply With Quote Share with Facebook
  #6  
Old 11-13-2010
Senior Member
 
Join Date: Jul 2006
Location: Corpus Christi, Tx
Posts: 1,045
Thanks: 18
Thanked 21 Times in 20 Posts
Rep Power: 9
ccriders is on a distinguished road
Thanks for your responses. I'm trying to keep track of battery status without replacing the current battery meter, which is worthless. The companionway outlet is very convenient and means I don't have to climb down into the cockpit locker, move a bunch of stuff open up the battery boxes and measure the batteries. There is probably six feet of 16ga wire (new) between the outlet and the terminal strip plus three feet of 16ga wire (new) between the switch panel and the terminal strip and then three feet of old wiring between the switch panel and the battery switch and six (?) feet of cable to the batteries. My guess that there has to be some voltage drop, but not significantly so. Based on the above comments a battery meter should be attached directly to the batteries, is that true? What gauge of wire should that be for say 10 -12 feet if wire?
Thanks for your help,
John
Reply With Quote Share with Facebook
  #7  
Old 11-13-2010
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,121
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
Yes, it is true a battery meter should be attached direct to the batteries.

A simple voltmeter will tell you voltage, but voltage is a lousy way to tell battery state. Ideally you can install a real battery monitor so you always know the exact state of charge of your battery bank. Like this:
Attached Thumbnails
Measuring Battery Voltage-1.jpg  
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
Reply


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 Voltage Issue sailak Gear & Maintenance 20 11-13-2009 09:21 AM
Any one usig the Gobius tank measuring device? SanDiegoChip Gear & Maintenance 3 08-06-2009 02:39 PM
Basic Battery Question - measuring capacity preservedkillick Gear & Maintenance 15 06-17-2009 03:37 PM
Battery Voltage verses amps dsbentley Gear & Maintenance 6 05-01-2008 10:16 PM
Measuring Boat Speed Dan Dickison Racing Articles 0 07-02-2002 08:00 PM


All times are GMT -4. The time now is 01:23 AM.

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.