View Full Version : Replacing Lead Acid Batts with AGM Batteries

01-11-2011, 10:18 PM
Happy New Year Forum,
I am done with the on-going battery issues I have been having in my coach and am going to replace the coach batteries with AGM's. I believe the batteries I have are not the right batteries for this application. I would appreciate any advice on what size AGM's (4D etc)to get and the best place to purchase them. Are the amp hours rated different on an AGM then on a lead acid battery? Thanks for your advice! Jennifer

01-12-2011, 12:41 AM
Refresh my memory, Jennifer, what kind of lead acid batteries do you have? Are they 8D?

01-12-2011, 12:55 AM
If you change over to AGM type Batteries you should change the Charge Voltage. Do a little research and be sure to up-grade the systems that should be up-graded. While some manufacturers will state that the Voltage should be the same as Flooded Lead Acid, this is incorrect to a purist.
The AGM is a superior Battery to a Gel or Flooded Lead Acid when it comes to maintenance although I believe that the other Manufacturers are still comparing to the TROJAN T105 (Flooded Lead Acid "Golf Cart" type) as the standard.

01-12-2011, 02:01 PM
Hi Clarke, I have Werker, Part # 12V215S. 228A.H. @20Hr, 75 amp rating, 115 min. They are not 8D. They are a lot taller than 8D's. I also have a new Progressive Dynamics charger. I believe it is the 9280 model. I cannot get a full charge out of the current batteries nor do they stay charged. I get about 7 hours of use and thats when I'm sleeping, and then they read below 12volts which is not good. Batteries plus tested them and they said they are fine. My hygrometer as well as others, says these batteries are no good. Steve, I will continue to research and thanks for the heads up on the Charge Voltage.

01-12-2011, 06:25 PM
It sounds to me, and I must add this disclaimer....I am an electrical novice, that there is some significant drain on the batteries, even when they are being charged, that is preventing them from fully charging. My gut says the problem is not the batteries, and that you must find what is discharging them as fast as they charge. Steve Ward is much sharper than I am on this, and perhaps he will tell me I am all wet, but it sounds to me like you have a short, or a really bad ground somewhere.

01-13-2011, 02:55 PM
Clarke, Perhaps this is true....How do I figure this one out? I'm okay with the minimal knowledge I have about electrical and as you know, electrical issues can be really expensive to figure out. I will have to investigate this further as to who I can find here in Missoula to help me figure this out. You may be right, however there is no significant drain showing on any of my meters. If I had a bad ground, would that show up anywhere else? I have charged these batteries independent of the coach and they just won't take a full charge. Thanks for your input Clarke! J

01-13-2011, 03:09 PM
Jennifer, sounds like we have to have a mini-rally to fix your problem.
Check with Richard, I believe he is heading up your way this year.

01-13-2011, 04:38 PM
Great Idea Forest!

Brad Townsend
01-14-2011, 01:12 PM
Life line 8D AGM's are the way to go. Do your homework on prices but at reputable places, there are chinese lookalikes out there. You could contact Life line for distributors in your area
if none then they may send them direct from there factory. Prices can range widely especially if the fake ones are included.
Your meters inside may show any draws on the power but you could also put an amp meter on the positive side of the battery bank, I think. I also have installed a Trimetric battery monitor Model #2020 which monitors everything to do with the batteries. Amp hrs used, Total amp hrs used on life of battery bank, volts, percent full, Amp draw as power is being used, battery high for the day, battery low for the day. This can be an intimidating unit to set up but well worth the time to learn. Many times the voltage reads in the high 14"s which some may think means the batteries are full but when checking the amp hrs there could be a deficit of maybe 40 amp hrs yet to be recovered. This is where folks get in trouble. The high voltage reading does not necessarily mean the batteries are full but that they have to sit at that high voltage for a longer time and without the monitor one can only guess. The monitor requires a 500 amp shunt total package could be $300. I replaced my house and coach batteries within 6 months which give me the option of merging both banks to double my amp hr capacity as long as I know I can recharge both banks when used. I try to exercise both banks hoping to keep them compatible with each other.
Check out the Life Line web site and even call them with questions.


01-14-2011, 03:31 PM
Try this out;

It is a clamp on amp meter. you can simply clamp it on the a battery cable and read the amperage draw from that battery.

Richard and Rhonda
01-14-2011, 07:58 PM
I had bad cells in two of my six batteries. The bank behaved exactly as you described, it would not charge fully and would not hold a charge. I charged the bank as best I could and then removed the interlinking cables. After a couple of hours it was evident using a volt meter which batteries didnt hold the charge. The hydometer confirmed both of the bad batteries had a bad cell. You really should let them sit overnight after charging before measuring. But it is critical to disconnect all the cables immediately after charging otherwise the bad batteries will drain the good ones and they will all be at the same voltage. Load testing is more accurate but this simple test may point in the right direction

02-18-2011, 09:33 PM
Here's the latest on my problematic coach batteries. The batteries Plus guy came out to the coach to investigate in person the problem. The batteries were charged and the coach plugged in when he got there. Within 20 minutes after unplugging the coach and turning on the fridge and some the lights, the batteries drew down from 12.8 to 12.2. He is now also scratching his head and agrees that something is not right. The amp draw during this process was 3 amps. Does anyone know what the original battery configuration was in 1987. I'm guessing it was 8D's. I wonder how many and where they were located. My battery compartment has been modified to fit these monster batteries that are in there now. Can any of you 1987 Newell owners take a picture of your battery compartment and post it and better yet, share with me what you have in your coach? There is a call into Newell to pick their brains as well. Thanks, Jennifer

Brad Townsend
02-19-2011, 12:34 AM
Hi Jennifer.
It is not unusual for the batteries to show a low reading under a load, especially if you are running the fridge along with the lights. What happens if you shut off the fridge and lights? Does the reading go back up? I don't think the guy from Batteries Plus is the proper person for such a problem. These coaches were designed with 8Ds 2 on the drivers side and 2 on the passenger side. The driver side is the house side the passenger side is the chassis side.

If you check you flood acid batteries with a hydrometer (the thing with 4 balls) it is more precise. Each ball equals 1/4. Example 4 balls floating in all cells = fully charged 3 balls= 75% full 2balls= 50% full and 1 ball = 25% full, actually instead of saying full it should be depth of charge.

As I stated before if you want a trouble free maintenance free dependable battery the go with 8D Life Line batteries. Thats my opinion.

But going further with your problem, you could have a load test done to see if the batteries
are ok, a carbon pile load tester is supposed to be the best so I have herd.


02-19-2011, 12:40 AM

If you decide to buy AGM batteries I have a friend whose company sells them at discounted prices.


His name is Tom; tell him Tuga recommended you to give him a call.

Richard and Rhonda
02-19-2011, 01:10 AM

Here is the first thing I would really look into. Twice you have posted that the batteries are fully charged, and the reading is 12.8. In my book, that ain't fully charged. You should be reading about 13 to 13.2 on fully charged.

I would try to analyze why. I can think of two reasons. One, the charger is not functioning properly. Check the output voltage of the charge. Two, you have a bad cell in one of the batteries. That would keep the whole bank from fully charging, and the whole bank would drop like a rock when you put a load on it. As others have said, check each cell with a hydrometer. Best way to do this is charge, take off charge, isolate each battery by removing the leads, and 24 hours later check each cell with a hydometer.

Checking with a hydrometer right after you take off the charger, and while all the bank is interconnected is not going to give you an accurate answer.

What I am describing is really not that much work.

Let us know what you find.

02-19-2011, 01:15 AM
Jennifer...I'll take pictures tomorrow when it stops raining and post them for you. My configuration is: Right front compartment - 2 8d batteries for the house. Right and left rear (just in front of wheel wells) 1 8d battery on each side. A total of 4 8d batteries....2 chassis and 2 house which may all be merged if needed.

02-22-2011, 04:15 PM
I like that thought! Find out what was the original wiring, size and location of the DC Batteries. If needed reconfigure to the original and then begin tested again. There could be some kind of gremlin running around.
Did you check the Battery Drain at the Batteries? or was this on an internal Meter?

I just wanted to add that I spent quite a few days removing 30 years of previous owner's wiring to our coach, I left all of that copper in a dumpster at an RV Park.

02-23-2011, 05:36 PM
Hey Steve, I checked the battery drain at the batteries. I agree with Richard, I think there is a bad cell in one these brand new batteries. I can't seem to get Batteries Plus to concur. They are just scratching their heads. This battery issue is a total hassle and completely frustrating with me not knowing enough to definitively diagnose and to be in Missoula, MT the middle of plain vanilla nowhere! I'll keep you posted. Jennifer