House Battery Issue

[123Bill]

I have a 2004 Winnebago Journey and upgraded my house batteries in June of 2018 to use three Cabela's 12V AGM DP Group 30 batteries connected in parallel. I also upgraded the converter charger at that time. All has been well until recently the batteries have started acting strangely. On two occasions now, when the batteries are fully charged, I have noticed significant voltage drops when loads are applied. I know voltage will always drop with load but this is extreme. For example, the voltage dropped from 12.5v to 11.9v with 15 min of TV viewing. I can usually watch TV all night. When the load is removed the battery recovers fairly quickly. After that occurrence the batteries worked well again for about a week. Then, last night the problem reappeared. Voltage drop was noticeable and significant with every type of load. The following morning, after resting the battery all night the voltage was 12.5v but it dropped to 11.5 when the generator was started. My charging system is working well. I have two installed voltage meters that show the same results and I used a portable meter across the battery terminals and got the same results as the installed meters. My battery terminals are tight and appear clean. Is this a battery problem? Can batteries have problems one day then work well the next. I need advice from a learned RV'er.

[BCam]

Here's a similar thread that may help:

https://www.irv2.com/forums/f59/batt...ad-177114.html

[wolfe10]

Where are you measuring battery voltage?


At the batteries?


If remotely, what is the connection-- if well toward the load, you could be getting false readings due to poor connections/small gauge wire.


Best to check at the batteries when this occurs. That will point you toward either the batteries or a problem further downstream.


A bit puzzling IF this happens with the converter or charger ON, as they should compensate for any draw within their amp rating.

[Mark_K5LXP]

Agree with above, sounds like a bad connection. A bad connection can be intermittent, but a bad battery that would cause the same symptom would not be. Could be right at the batteries or anywhere along the path between the batteries and the load. Using a voltmeter along that path with the load applied will reveal where the issue is.

Mark B.
Albuquerque, NM

[sailorman1]

If not a bad connection, which wouldn't take 15 minutes to show and wouldn't change voltage at the batteries, the likely problem is that batteries have lost capacity. If you only basis of batteries being "fully charged" is voltage you have probably been undercharging them a long time and now they they are sulfated.

[lrgomez1976]

Your batteries are only as good as your bad one. May want to have them individually load tested. Also add a battery cut off switch when not in use. You will be surprised the little things running in the background that run off the batteries.

[123Bill]

Thanks for the input and sorry for taking so long to respond. I spent the last two weeks in Northern Maine without internet connections. I am still having battery issues and have done a few checks. I checked the voltage at the battery terminals when the battery was under load and found the voltage at the terminals matched the voltage readings I get inside the coach which was 12.5v at the time. I then opened my battery disconnect switch, disconnected all my battery cables and checked the voltage across individual batteries and got 12.7v of each one. I cleaned the dirt and tarnish off my cables and reconnected the cables. With my battery bank disconnected from the coach I got 12.7v across the bank. I then closed my battery disconnect switch to connect the battery bank with the coach and got 12.5v at the terminals and inside the coach with no significant load.

Since then, I am still having reasonable battery power at times and poor performance at others. Since my battery terminal voltages closely match the voltages inside my coach and don't think loose connections are my issue. My charging system is working so I believe I likely have a battery problem of some sort. I plan to take it into a battery shop for a load test and to consult with the technicians. My Cabela AGM batteries are only three years old. I use my coach about 50% of the time but I expected the batteries to last much longer.

I plan a further update after I have the batteries tested. If I need new batteries, I don't know what is best considering the AGM's only lasted three years. I am thinking of going the less expensive lead acid route.

[Mark_K5LXP]

I don't think a load test is going to tell you much about the merit of your batteries. That kind of test is more suited for starting, not storage batteries.

You can test storage batteries fairly easily yourself and get an actual number of merit by doing a timed discharged test, and comparing your result to what the manufacturer spec's for those batteries. That is the real number you're looking for and with that you can determine if it's the battery or some other issue you need to address.

Generally, batteries that give up before they're used up or age out is due to a charging issue, either chronic over or under charging. So before I'd commit to any new batteries I'd be going over the charging and storage regimen you follow and find out what's damaging them.

Mark B.
Albuquerque, NM

[rffowler55]

The voltage drop under load is the number one warning flag I use for assessing my batteries that are associated with my off-grid solar backup system we have at our home. As stated, you could have one battery that has shorted out which would impact the entire systems ability to provide sufficient power under a load. I recommend doing an internet search on how to test your batteries to see if they are in good working order before replacing or looking into charging issues since a bad battery will also impact the entire charging process since the charger will attempt to bring the entire battery bank up to full charge and a bad battery will potentially require a much higher charge rate and will over charge the remaining batteries.

[mr.tommy]

Originally Posted by 123Bill

For example, the voltage dropped from 12.5v to 11.9v with 15 min of TV viewing.

You didn't mention whether your plugged into shore power or not but it sounds to me like your boon docking since you mentioned the generator and being up in Maine...

If your not plugged into shore power—like I suspect—then that means your using your inverter to power things. Just turning the inverter ON alone will start to draw quite a few amps. Probably in the range of 7-9amps or so. Now you turn on the TV, the Fridge is drawing amps, TV antenna, and anything else that runs off 12V or the inverter. Plus your converter isn't running and charging the batt's all that time either until you start the generator. So given all this, I can see your batteries losing charge somewhat rapidly. Your batt's are 3yrs. old and even though that's not considered old by any means, they do lose charge and load capacity little by little over time. In other words, they just don't work like they used to when they we're young. Kinda like us.

I have Lead Acid Trojan 6V batt's wired in series. This past winter they were 4yrs. old and I take really good care of my batt's and they always worked great. UNTIL...this past winter. They we're starting to lose their full ability to last a long time on a charge. They we getting weak because of age and since we're FTer's they've gone thru many cycles over the past 4yrs. And I have a 4 stage converter. Now don't get me wrong, they still worked fairly good, but not like they once did. I need reliable, fully charged batt's with full available amp hours that I know will get us thru. I changed them out this winter for new ones. Everything is back to normal as it once was.

[757driver]

Originally Posted by 123Bill

Thanks for the input and sorry for taking so long to respond. I spent the last two weeks in Northern Maine without internet connections. I am still having battery issues and have done a few checks. I checked the voltage at the battery terminals when the battery was under load and found the voltage at the terminals matched the voltage readings I get inside the coach which was 12.5v at the time. I then opened my battery disconnect switch, disconnected all my battery cables and checked the voltage across individual batteries and got 12.7v of each one. I cleaned the dirt and tarnish off my cables and reconnected the cables. With my battery bank disconnected from the coach I got 12.7v across the bank. I then closed my battery disconnect switch to connect the battery bank with the coach and got 12.5v at the terminals and inside the coach with no significant load.

Since then, I am still having reasonable battery power at times and poor performance at others. Since my battery terminal voltages closely match the voltages inside my coach and don't think loose connections are my issue. My charging system is working so I believe I likely have a battery problem of some sort. I plan to take it into a battery shop for a load test and to consult with the technicians. My Cabela AGM batteries are only three years old. I use my coach about 50% of the time but I expected the batteries to last much longer.

I plan a further update after I have the batteries tested. If I need new batteries, I don't know what is best considering the AGM's only lasted three years. I am thinking of going the less expensive lead acid route.

How are you charging your batteries when they are low? What voltage are you charging to, how long are they staying at that upper voltage (prior to going to float), how many hours are you charging for at a time?

[Persistent]

Symptoms
The batteries hold 12.7 when disconnected.
The batteries hold 12.5 when connected.

This is normal battery behavior. There are three basic profiles for lead acid batteries.

Static Profile
Static profile is the voltage when not charging or discharging for some time. Voltage stabilizes after a while. This voltage can be used to determine battery state of charge. 12.7 is fully charged. See table below.

Charging Profile
Charging voltage is always higher than static voltage. Charging profile depends on the battery bank size and the charger capabilities. Voltage starts at the state of charge voltage and slowly rises. It could start at 11.2 volts. The voltage will rise to the voltage the charger provides. Different chargers have different behaviors. Volt may rise to 13.3, 13.6, or 14.4 volts.

It may take 4 hours to reach the charger set point. Relatively higher capacity chargers rise faster. At this point the voltage will be stable for a while. Batteries are not fully charged at this point.

So my WFCO 30 amp charger can bring a 70 amp hour battery to 14.4 volts in a couple of hours. It holds that voltage for up to 4 hours. It then drops to 13.6 volts and stays there indefinitely. The same charger working on a 200 amp hour battery bank does not reach 14.4 volts inside the allowed 4 hours so it raises to 13.6 and stays there.

Discharging profile
Discharging profile is always lower than static profile. The greater the discharge, the lower the voltage. Voltage slowly raises when discharge stops.
Engine start battery voltage does not drop as much as deep draw batteries given the same discharge rate.

12.5 volts on a deep draw battery with 12.7 volt static is being moderately discharged. A 2000 watt inverter supplying 1000 watts would pull most 200 amp hour deep draw batteries down below 11.2 volts. Voltage would slowly raise back to 12.7 volts when discharge stops.

In all charging cases it takes 14 to 18 hours to fully charge a lead acid battery. Lead acid batteries must be fully charged before storage for long health performance.

Aging batteries
Lead acid batteries age very little over time. They do "age" based on how often and how much they have been charged and discharged. Many can be discharged to 10% state of charge and fully recharged 300 to 400 times. If you only draw them down to 50% state of charge you can get twice as many charge cycles.

Battery University https://batteryuniversity.com/articles

How does the Lead Acid Battery Work?
https://batteryuniversity.com/articl...d-battery-work

How do battery chargers work
https://batteryuniversity.com/articl...-chargers-work

How to Charge and When to Charge?
https://batteryuniversity.com/articl...when-to-charge

"static" state of charge.
100% 12.7
90% 12.5
80% 12.42
70% 12.32
60% 12.2
50% 12.06
40% 11.9
30% 11.75
20% 11.58
10% 11.31
0% 10.5

[123Bill]

Thank you to everyone that responded. I have learned a lot and you have helped greatly. Here is a summary of where I stand today.

Background:
I have three Cabela 12v AGM batteries (probably ~105 Amp Hr each). These batteries power my lights, tv components, fans, electric motion chair, control power and not much else in my camper. I have a 70 Amp three stage smart charger. My goal when I installed them was to be able to boondock without battery worry and then recharge within a few hours each day. This goal seemed to be met for the first two years. I removed my batteries in the winter and fully charged them in my home during storage. Last winter I got lazy. I disconnected the ground wire and left them in the camper. I think AGM batteries will not freeze so I thought that would be OK. I don't know if that damaged my batteries of if something else caused my problems this year.
My batteries seem harder to charge and more quickly loose voltage. Sometimes the problem seems worse than others. At times, I can charge them for hours and only get two hours of use out of them. Other times I can go all day. My charging system is working and I have tested voltages at the battery terminals.

Testing:
Based upon the inputs I received I searched the internet for ways to best test my batteries but did not find much of use. I decided to charge the batteries for an extended period (until the coach readings were 14v). Then I disconnected all the "A" battery and tested it's voltage (13v). My plan was to take the batteries off line one at a time rest them check voltage after 24 hours and take them for a load tests. Also, I planned to see how well the remaining two batteries performed in the camper over that time. Hopefully, only one battery would turn up bad. The "A" battery held voltage at 12.8 after 24 hours. It did not pass the load test at it's rated 774 CCA but did pass at Winnebago's specified 665 CCA. I was told the battery was in it's last 25% of life. The "B&C" batteries performed much worse in my camper than my full bank performed. So, after day one, I surmised that battery "A" should be good and one or both of my other two batteries was bad.

Change of plans. I then decided to re-connect battery "A" to the camper charge all three batteries back to 14v and then remove both battery "B" and "C" for testing. I left the camper sit all day with battery "A" connected and no inverter, lights or other loads turned on. After six hours, battery "A voltage dropped to 12.4v and battery "B" and "C" voltage was holding at 2.9v. Okay, now I know battery "A" has some problem and at least one or both batteries "B" and "C" have a problem. At that point, I terminated testing. I plan to replace all three batteries.

Summary,
I still do not know what caused my three year old AGM batteries to fail and I have some concern that something in my camper may be pulling the batteries down even with nothing turned on. I am going to buy new batteries and see if my problems go away!

Thanks again.
Bill Pifer
2004 Winnebago Journey

[Mark_K5LXP]

A capacity test for lead storage batteries amounts to doing a complete charge cycle, then putting a known load on it and observing the time it takes for the voltage to reach 10.5V. Since most batteries are spec'd at the 20 hour rate, you'd apply a load that matches that and the battery should run for 20 hours. So for your 105Ah batteries you'd use a 5.25A load. A new/good battery will go 20+ hours, as the battery wears and ages it will deliver less. So if your battery only runs 15 hours, it's about 75%, 10 hours, 50%. Generally a healthy battery will deliver >80% for most of it's life, then drop more rapidly towards the end. A battery at 50% typically has very operating life left. Since you have three separate 12V batteries you would run a capacity test on each one to see what their individual merit would be. From there you can decide whether they're still serviceable.

Presuming they've gone south, if you don't figure out what it is about your operating regimen that's causing them to fail, the next set won't fare any better.

Mark B.
Albuquerque, NM