Reply
 
Thread Tools Search this Thread Display Modes
 
Old 07-03-2017, 06:31 PM   #1
MollyMac
 
2017 25' Flying Cloud
Hoover , Alabama
Join Date: May 2016
Posts: 8
Battery reading

I am so new and now confused. What should my battery read when I press the monitor button. I have a FC25 FB with Group 24 w/converter 2 deep cycle 2 batteries. I am nervous that I have run the battery down.
MollyMac
__________________

__________________
MollyMac is offline   Reply With Quote
Old 07-03-2017, 07:16 PM   #2
Rivet Master
 
Wingeezer's Avatar
 
2005 30' Classic
Burlington , Ontario
Join Date: Sep 2008
Posts: 2,666
From memory, I think around 12.7 is fully charged, and about 12.3 is 50%

When your battery is being charged by the trailer you will likely read around 14v+.

The battery will stay high for at least a few hours after a charging session so you must wait a while to let it settle down before taking a reading to determine its actual state of charge.
__________________

__________________
Brian & Connie Mitchell

2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.
Wingeezer is offline   Reply With Quote
Old 07-03-2017, 07:20 PM   #3
Half a Rivet Short
 
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 2,405
Hi

The real question is "what should the battery read at the battery terminals when read with a multimeter?". Reasonably accurate multimeters are quite cheap. The monitor screens on the typical RV are grossly inaccurate in many cases. Read the battery, check the screen and come up with the "offset" between them. Once you have done that (reads half volt high...) you can to a lot better working out what's going on.

Bob
__________________
uncle_bob is offline   Reply With Quote
Old 07-03-2017, 09:08 PM   #4
MollyMac
 
2017 25' Flying Cloud
Hoover , Alabama
Join Date: May 2016
Posts: 8
When I got it from the storage place it was reading 12.1...I drove home to pack up. Checked it at 8:00 pm....it was at 9.1...very concerned
__________________
MollyMac is offline   Reply With Quote
Old 07-03-2017, 09:13 PM   #5
3 Rivet Member
 
dmbecke's Avatar
 
Currently Looking...
Des Peres , Missouri
Join Date: May 2016
Posts: 118
I had the same issue on a 2014 recently purchased
Sounds like you need new batteries
How long since their last charge?
__________________
dmbecke is offline   Reply With Quote
Old 07-03-2017, 09:25 PM   #6
Half a Rivet Short
 
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 2,405
Hi

Charging off of the TV is not likely to be very effective. If you get a 10A current from the tow, that's doing very well (you might get zero). At a 10A constant rate (which you will never see), it will take 10 hours of driving to charge a "half dead" battery. That's all with nothing pulling current in the AS. If you have the fridge and a few other things turned on, you might double or triple that.

Plug in to shore power, charge for at least a day, see where you are at.

Bob
__________________
uncle_bob is offline   Reply With Quote
Old 07-04-2017, 05:55 AM   #7
Rivet Master

 
2014 20' Flying Cloud
Long Island , New York
Join Date: Jun 2015
Posts: 5,686
Quote:
Originally Posted by MollyMac View Post
When I got it from the storage place it was reading 12.1...I drove home to pack up. Checked it at 8:00 pm....it was at 9.1...very concerned
When you got 9.1 were there any 12-volt functions running? If so, turn everything off, wait an hour or so after shore power is removed per earlier comment, and then check again.

12.1 represents batteries at about 40% of capacity +/-. Below that more serious damage starts to occur.

The earlier posters and uncle bob have good advice IMO:

Quote:
Originally Posted by uncle_bob View Post
Hi

Charging off of the TV is not likely to be very effective. If you get a 10A current from the tow, that's doing very well (you might get zero). At a 10A constant rate (which you will never see), it will take 10 hours of driving to charge a "half dead" battery. That's all with nothing pulling current in the AS. If you have the fridge and a few other things turned on, you might double or triple that.

Plug in to shore power, charge for at least a day, see where you are at.

Bob

You can take the batteries into an Interstate battery store [assuming this is your brand] to have them tested. This Battery School site is good background reading:

http://www.batteriesnorthwest.com/ba...ool.cfm?TID=10

Good luck!

Peter
__________________
OTRA15 is offline   Reply With Quote
Old 07-04-2017, 06:11 AM   #8
3 Rivet Member
 
fran&frank's Avatar
 
2016 27' Flying Cloud
Hartsburg , Missouri
Join Date: Dec 2015
Posts: 186
If you run your batteries down below 50% discharge you don't instantly kill them but you do reduce their service life. Just get them up to fully charged ASAP.-- Frank
__________________
Frank & Fran
2016 27' FC FB with 400 W solar
2016 Ford F150 EcoBoost
Equalizer Hitch
fran&frank is offline   Reply With Quote
Old 07-04-2017, 08:38 AM   #9
Rivet Master
 
richw46's Avatar
 
2006 23' Safari SE
Lexington , Kentucky
Join Date: Dec 2012
Posts: 2,062
Images: 6
State of Charge

I found this article on the state of charge for batteries a while back. I've printed and put inside a clear page cover so I could add it to my AS book.
Attached Files
File Type: pdf State of Charge.pdf (36.6 KB, 28 views)
__________________
-Rich

Rich & Yvonne
2006 Safari SE -Dora-
2004 4Runner SE

richw46 is offline   Reply With Quote
Old 07-05-2017, 06:59 AM   #10
Half a Rivet Short
 
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 2,405
Quote:
Originally Posted by richw46 View Post
I found this article on the state of charge for batteries a while back. I've printed and put inside a clear page cover so I could add it to my AS book.
Hi

If you are going to get into the details of charge vs voltage:

1) The voltage readings on the monitor panels have been reported to be more than a half volt off in one direction or the other. Don't use those numbers until you have checked the readings against a good multimeter.

2) Voltage numbers matter on a *quiet* battery. Charging and discharging both distort the readings. Measuring through wires that are doing charging or running a load distorts the numbers. Wait at least a half hour after charging is done before reading voltages.

3) The voltages and the capacity of the batteries change quite a bit as the temperature of the batteries changes. For normal temperatures it's > 0.5V. A battery sitting out all day in the desert sun may be fully charged and have a voltage reading that is pretty poor.

So what's the answer?

One way to figure out how a battery is doing are specific gravity readings. They will give you another way to see what's going on.

A "better" way to figure out how much battery you have is a monitor that reads the current into the batteries, adds it all up and compares it to the current out of the batteries. They aren't perfect, but they are way better than voltage readings.

Monitoring battery temperature for charging is a *very* good idea. That will also improve your capacity / voltage estimates.

Get a multimeter. It will come in handy for a number of things. They aren't very large. A really good one is < $100. One that is "good enough" is < $20.

Lots to think about.

Bob
__________________

__________________
uncle_bob is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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
Reading battery monitor Pyle Airstream Motorhome Forums 3 01-04-2016 02:57 PM
Reading the serial number question tiniree Our Community 10 10-30-2015 11:49 AM
Replace "Reading lights" with real reading lights and fans? Belbein Airstream Lifestyle 0 06-08-2014 12:30 PM
Fix that "wrong" battery reading meter!! lebolewis Batteries, Univolts, Converters & Inverters 6 06-24-2006 06:44 AM
Looking for some good reading material!! John Off Topic Forum 14 02-25-2003 10:02 AM


Virginia Campgrounds

Reviews provided by



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- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 03:30 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.