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

Go Back   iRV2 Forums > MOTORHOME FORUMS > Class B Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 01-19-2025, 03:17 AM   #1
Junior Member
 
Join Date: Sep 2024
Posts: 6
AGM how low is to low?

All,

I recently purchased a new Dazzle Class B rv. It has 2 100ah AGM batteries installed. I’m noticing that when I run the heater and tank heaters at night that the voltage level indicators for the batteries will show the yellow caution flag for low voltage. I caught this in the middle of the night while camping in 25 degree temps. I setup the auto start feature on the genny to start up around 11.8 volts if I remember right.
It will also show that if I’m only running the furnace but less frequently.
With the furnace and tank heaters on it will start the genny multiple times overnight to recharge the batteries. I have it set to only run for an hour each time.
What is the safe minimum voltage for AGM batteries? To me, they don’t seem to keep their charge for very long compared to Lifepo4. I had a toy hauler that I setup with 200 amps of Lithium and I never came close to that kind of voltage drop at night. But, I also didn’t have tank heaters in the toy hauler. Just a furnace.
I’m contemplating converting to lithium batteries but I don’t want to void any warranty on anything.

At what voltage level will the AGM batteries become damaged?

Thanks..

Don.
D308 is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 01-19-2025, 07:34 AM   #2
Senior Member
 
Join Date: Jul 2014
Posts: 37,095
When you hit 11.8 volts with the tank heaters or anything else running, that's not an accurate reading.

Checking a batteries state of charge under load doesn't work. The battery need all loads removed and sit for 2 to 3 hours before a voltage reading, for capacity, can be made.

Reset your AGS for 11 volts and see how it works out, a full discharged battery is 10.6 resting volts.

A better solution is a battery monitor, it's like a gas gauge for your batteries.

As far as recharging, if your discharging to 50%, that's 100 AH. With a 50 amp charger, it will take a minimum 2.5 hours to get them recharged near full.
twinboat is online now   Reply With Quote
Old 01-19-2025, 10:38 AM   #3
Senior Member
 
ttavasc's Avatar


 
Ford Super Duty Owner
Outdoors RV Owners Club
Jayco Owners Club
Join Date: Jun 2018
Location: Auburn, WA
Posts: 809
Quote:
Originally Posted by D308 View Post
All,

I recently purchased a new Dazzle Class B rv. It has 2 100ah AGM batteries installed. I’m noticing that when I run the heater and tank heaters at night that the voltage level indicators for the batteries will show the yellow caution flag for low voltage. I caught this in the middle of the night while camping in 25 degree temps. I setup the auto start feature on the genny to start up around 11.8 volts if I remember right.
It will also show that if I’m only running the furnace but less frequently.
With the furnace and tank heaters on it will start the genny multiple times overnight to recharge the batteries. I have it set to only run for an hour each time.
What is the safe minimum voltage for AGM batteries? To me, they don’t seem to keep their charge for very long compared to Lifepo4. I had a toy hauler that I setup with 200 amps of Lithium and I never came close to that kind of voltage drop at night. But, I also didn’t have tank heaters in the toy hauler. Just a furnace.
I’m contemplating converting to lithium batteries but I don’t want to void any warranty on anything.

At what voltage level will the AGM batteries become damaged?

Thanks..

Don.
Bear in mind that the lithium batteries maintain a higher voltage under load over a longer period of discharge than FLA or AGM. You can see on the voltage chart below that they remain well above 12v until nearly discharged. That would explain the difference in behavior that you've observed between the two campers.
Attached Thumbnails
Click image for larger version

Name:	Screenshot 2025-01-19 at 08.34.13.png
Views:	4
Size:	300.3 KB
ID:	434130  
__________________
TT: 2019 ORV Timber Ridge 23DBS, Blue Ox SwayPro 15K/1500
TV: 2019 Ford F-250 XLT SuperCab LB, 6.2L, 4.30/e-locker, 4x4, 164" WB, RoadActive Suspension
ttavasc is offline   Reply With Quote
Old 01-19-2025, 11:39 AM   #4
Senior Member
 
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 5,904
The biggest difference between the two campers is most likely the load being consumed. Those tank heaters use a lot of power.

I had 12 volt tank heaters in my Kodiak Cub. I quickly found out that 12 volt tank heaters were not practical with only 200 amp hours of AGM batteries.

I sealed and insulated the belly area and heated it all using a duct from the propane furnace. Results were much better.

Battery charging

Lead acid batteries typically require 14 hours or more for a full charge. 4 hours with a good quality charger may get an 80% state of charge. 1 hour gets next to no charge.

Good advice posted above about using a current measuring (Coulomb Counter) system for starting the generator. Heavily loaded lead acid batteries are not going to present good data using voltage alone.
__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
Persistent is offline   Reply With Quote
Old 01-19-2025, 01:13 PM   #5
Junior Member
 
Join Date: Sep 2024
Posts: 6
Thank You

Thanks to everyone for the advice.
D308 is offline   Reply With Quote
Reply

Tags
agm



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
AGM 1 or AGM 2 lmcbean0601 Monaco Owner's Forum 2 09-12-2019 05:01 PM
AGM Batteries/AGM Batteries Floridakamper Winnebago Industries Owner's Forum 8 09-19-2016 07:26 AM
AGM or low maintence Mr_D Country Coach Owners Forum 12 06-16-2015 09:48 PM
When are AGM's not AGM's? bokobird iRV2.com General Discussion 39 09-24-2014 09:59 AM
AGM Batteries, Are You Happy With Your AGM's? Are They The Answer? Lug_Nut Newmar Owner's Forum 36 11-25-2007 08:59 AM

» Featured Campgrounds

Reviews provided by


All times are GMT -6. The time now is 12:47 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2025, vBulletin Solutions, Inc.