Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 
 


Reply
 
Thread Tools Display Modes
 
Old 08-01-2015, 03:29 PM   #1
Platinum Member
 
Join Date: Dec 2010
Posts: 2,058
Default 50 percent agm voltage

hey smart people- i have a question about AGM batteries.

what voltage is considered 50 percent -just wondering
gerrym51 is offline   Reply With Quote
Old 08-01-2015, 04:05 PM   #2
Platinum Member
 
Join Date: Feb 2015
Location: Chaska MN
Posts: 1,700
Default

Would it be different from other batteries? (which would be about 12.0) Or is that your question that I can't answer...
__________________
2021 Promaster 1500 118wb conversion
2019 Roadtrek Simplicity SRT (almost a Zion)
2015 Roadtrek 170
2011 LTV Libero
2004 GWV Classic Supreme
mumkin is offline   Reply With Quote
Old 08-01-2015, 06:16 PM   #3
Platinum Member
 
wincrasher's Avatar
 
Join Date: May 2014
Location: Greer, South Carolina
Posts: 2,611
Default

__________________
2019 Winnebago Travato GL
Follow my blog: https://www.wincrasher.blogspot.com
Our Facebook group is: https://www.facebook.com/groups/ClassBCamperVans/
wincrasher is offline   Reply With Quote
Old 08-01-2015, 06:53 PM   #4
Platinum Member
 
Boxster1971's Avatar
 
Join Date: Mar 2012
Location: Maryland
Posts: 1,183
Default

Quote:
Originally Posted by wincrasher View Post
Where did you get that voltage chart? It does not match the data from Lifeline AGM that I have. The 100% voltage on Lifelines is 12.8V.
Boxster1971 is offline   Reply With Quote
Old 08-01-2015, 06:59 PM   #5
Platinum Member
 
wincrasher's Avatar
 
Join Date: May 2014
Location: Greer, South Carolina
Posts: 2,611
Default

There are alot of variations on this chart online. Just google "battery voltage chart" and you'll see tons. I consider them a rough approximation at best.
__________________
2019 Winnebago Travato GL
Follow my blog: https://www.wincrasher.blogspot.com
Our Facebook group is: https://www.facebook.com/groups/ClassBCamperVans/
wincrasher is offline   Reply With Quote
Old 08-01-2015, 07:17 PM   #6
Platinum Member
 
markopolo's Avatar
 
Join Date: Oct 2006
Location: New Brunswick, Canada
Posts: 8,828
Default

Here's a chart I found on Phillips Industries site. It was part of some load testing instructions which wanted to ensure that you recharged the battery if below 75% state of charge before load testing the battery.

Phillips State of Charge chart flooded and agm.JPG
markopolo is offline   Reply With Quote
Old 08-01-2015, 10:02 PM   #7
Platinum Member
 
Join Date: Dec 2010
Posts: 2,058
Default

how low is an agm battery if an inverter sounds alarm at 10.5 and shuts off at 10 volts
gerrym51 is offline   Reply With Quote
Old 08-01-2015, 10:45 PM   #8
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,919
Default

Quote:
Originally Posted by gerrym51 View Post
how low is an agm battery if an inverter sounds alarm at 10.5 and shuts off at 10 volts
It all depends on how much current the inverter and loads are taking out of the battery at that time.
booster is offline   Reply With Quote
Old 08-01-2015, 10:59 PM   #9
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,919
Default

Here is a chart from Lifeline that shows what the voltage will read at a given state of charge, when being discharged at various rates.

This is a very useful chart for setting low voltage cutouts and alarms.

Attached Images
File Type: jpg Lifeline volts vs discharge rate.jpg (87.4 KB, 62 views)
booster is offline   Reply With Quote
Old 08-01-2015, 11:03 PM   #10
Platinum Member
 
wincrasher's Avatar
 
Join Date: May 2014
Location: Greer, South Carolina
Posts: 2,611
Default

Quote:
Originally Posted by gerrym51 View Post
how low is an agm battery if an inverter sounds alarm at 10.5 and shuts off at 10 volts
Low enough to destroy your battery I would think.
__________________
2019 Winnebago Travato GL
Follow my blog: https://www.wincrasher.blogspot.com
Our Facebook group is: https://www.facebook.com/groups/ClassBCamperVans/
wincrasher is offline   Reply With Quote
Old 08-01-2015, 11:26 PM   #11
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,919
Default

Quote:
Originally Posted by wincrasher View Post
Low enough to destroy your battery I would think.
I think that would depend on the battery type and brand (10.5v or 10.0 shutoff)

From the lifeline chart, it sure looks like it would hurt them, but I know I could drag down our wet cell Trojans to 10 volts when at even 50% state of charge, by pulling lots of current, so those would probably survive just fine.
booster is offline   Reply With Quote
Old 08-01-2015, 11:51 PM   #12
Platinum Member
 
Join Date: Dec 2010
Posts: 2,058
Default

I know this will be stupid is the low voltage cutoff in an inverter there to save the battery or the inverter. if it's there to save the battery how come it's set at 10 volts.

is it actually 10 volts or is 10 volts what it predicts the rate of inverter use will cause.
gerrym51 is offline   Reply With Quote
Old 08-01-2015, 11:56 PM   #13
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,919
Default

The voltage for the cutoff would normally be what the predicted voltage would be with the inverter running it's biggest load and the battery at the lowest SOC you want to be at and still be able to run the inverter.
booster is offline   Reply With Quote
Old 08-02-2015, 12:13 AM   #14
Platinum Member
 
Join Date: Dec 2010
Posts: 2,058
Default

Quote:
Originally Posted by booster View Post
The voltage for the cutoff would normally be what the predicted voltage would be with the inverter running it's biggest load and the battery at the lowest SOC you want to be at and still be able to run the inverter.
so it's predicted voltage not actual voltage?
gerrym51 is offline   Reply With Quote
Old 08-02-2015, 12:27 AM   #15
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,919
Default

It is predicted in the sense that the inverter makers guess what batteries and loads you will have.

For best accuracy for your system you just need to run a test to find out what the real life voltage would be.

1. Decide what the minimum SOC you want to have and still be able to run the inverter.

2. Discharge your batteries to that SOC

3. Run you biggest, or typical, load through the inverter, with all your regular 12v loads on at the same time

4. See what the voltage reads under the those inverter running conditions.

5. Set the voltage you saw as your low level cutoff.

Done
booster is offline   Reply With Quote
Old 08-02-2015, 12:30 AM   #16
Platinum Member
 
wincrasher's Avatar
 
Join Date: May 2014
Location: Greer, South Carolina
Posts: 2,611
Default

Actually, what he's saying is that it's set to account for the voltage drop attributed to your loads with the inverter running. In my recent tests, all my heavy loads totaled 1/2 a volt in voltage drop.

I still say that is too low. Even 11 volts is too low for an AGM. I'd set your cutoff above 11.5 for your AGMs. When you get your tandem, I have no clue, but maybe you can go lower.
__________________
2019 Winnebago Travato GL
Follow my blog: https://www.wincrasher.blogspot.com
Our Facebook group is: https://www.facebook.com/groups/ClassBCamperVans/
wincrasher is offline   Reply With Quote
Old 08-02-2015, 12:40 AM   #17
Platinum Member
 
Join Date: Dec 2010
Posts: 2,058
Default

i have seen many people with e-trek and e-trek packages complaining that the inverter turns off and battery still shows good charge-i know idiiot lights are not perfect.

what i was trying to determine is if the inverter is shutting off at 50 percent.

the inverter specs say low voltage alarm at 10.5 volts and shut off at 10 volts

yet it seems to be happening a lot sooner
gerrym51 is offline   Reply With Quote
Old 08-02-2015, 12:45 AM   #18
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,919
Default

Quote:
Originally Posted by gerrym51 View Post
i have seen many people with e-trek and e-trek packages complaining that the inverter turns off and battery still shows good charge-i know idiiot lights are not perfect.

what i was trying to determine is if the inverter is shutting off at 50 percent.

the inverter specs say low voltage alarm at 10.5 volts and shut off at 10 volts

yet it seems to be happening a lot sooner
You just need to run the test I listed and you will know for sure.
booster is offline   Reply With Quote
Reply

Thread Tools
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


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 12:27 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.