I killed them-but how?

[WalkaboutTed]

I committed batterycide.   But I really don't know how it happened and I'm turning to collective wisdom here for possible answers.  So, bear with me.

History:  I have 300ah of the el cheapo UPG 121000 AGM batteries in my van (Blanca).   I've had them almost 3 years, with no problems and never going below 60-70%.   I have them powered with 420w of solar with a BlueSkies 3000i charge controller.  I also have a CTEK d250s and a SmartPass, though they have no part in this mystery. 

I left the van parked for 5 weeks while I went off to gallivant with Hubby.  The batteries  were fine (between the three vehicles, I have 1150ah of AGMs and I watch them like hawk and make sure that they always are taking in about 1amp per 100ah before I let them go to float). During the 5 weeks, Blanca was parked where she got full New Mexico desert sun about 5 hours a day.  The only battery drain was the fridge, which uses about 50ah a day (I've measured it multiple times).  

Since Blanca wasn't getting full sun every day, nor was she getting any power from the alternator,  I decided to put on a trickle charger, a CTEK Multi 3300, which will supply up to 3.5 amps/hour. I figured that the sun would do most of the charging with the trickle charger making up the balance.

So we got back last night. The batteries were at 13.2v. Hmmm. So I unplugged the charger and they dropped to 12.8v immediately.  Uh-oh!  I set the alarm for 0430, before sunrise. 11.9v!

So what happened?  I've not checked anything else in the 15 hours I've been home yet, but suggestions of what to do are welcomed. Thank you!

 

[B and C]

I could be mistaken but I think .5 amps per 100 AH is where float should be set. It has been a couple of years since I even looked at my controller settings.

13.2 is float voltage and 12.8 is normal battery voltage (without load) and would be about right under load immediately after disconnecting charging source. I think dropping to float too soon is your problem as your batteries are not getting fully charged. Your alternator has probably been taking up the slack.

 

[XERTYX]

I dont know anything about that charger. Does it support AGM or only flooded perhaps? Was it always providing 3.5 amps charging? Or does it have an over voltage disconnect?

I'm very sorry to hear of your misfortune.

 

[Trebor English]

While you were gone did the AC power go out and come back on? If that happened there was nobody there to select the charging mode when the power came back on.

When you got back was the display showing the half full battery (charge mode), the full battery (maintenance charge mode), or the green light (full)?

How has the CTEK 3300 reacted previously when the fridge compressor started? Sometimes smart chargers see the battery voltage drop and decide that there has been a fault of some sort and then quit.

According to page 7 of the manual:
"Caution: If the MULTI US 3300 does not switch to maintenance charge mode after three days, manually switch it to pulse maintenance mode. If the set has been switched to maintenance charge, then everything is in order. Note: A battery that hasn't changed to maintenance charge after three days is most likely worn out and needs to be replaced. All other batteries can be maintained for a very long time"

The fridge may have confused the CTEK smart charger.

A modern good RV converter/charger is designed to supply 12 volts to varying loads and charge the battery without roasting it. That's not a maintainer or smart charger. It is a different thing.

Try separating the three batteries. There may be just one that's bad.

 

[Elbear1]

People with motorcycles do this all the time. They leave a float charge on through winter. AGM doesnt self-discharge much at all AND they have very little fluid available to boil off..hence absorbed glass mat. So every spring they run out and buy a "good" AGM an accept a year is all they last and come fall they plug them in again and fry them. They will take a charge and fall on their face under load.

The trickle charge dries them out.

 

[tx2sturgis]

You're going to have darts landing all over the map with this one.

Here are my two guesses:

First (less expensive) guess: Double check the terminals, fuses, connectors, especially at the battery terminals: Sometimes sitting motionless for several weeks, with no heavy currents, the metal to metal terminals oxidize and fail or go intermittent. Loosen then tighten all the battery terminal nuts. If you see any signs of dull metal, graininess, greenish or grayish powder etc, remove, clean, treat with your choice of dielectric grease, coating, or de-oxidizer, and reinstall.

Second (more expensive) guess: Those batteries are not known for long life...they ARE cheap...in fact, 3 years of daily drops to 60-70 percent is probably about it. 

I hope its the former. But it might be the latter.

 

[skyl4rk]

12.8V is a full charge for batteries with no charger connected.

 

[jimindenver]

There are a variety of things possible. One battery going bad will suck the life out of the other two and likely damage them. Even if it did not cause damage you can not put a new battery with a pair of three year olds so the bank is bad.

13.2v is not float voltage on your bank unless it is really hot and your devices a temperature compensated. 12.8 is full on a FLA bank but generally AGM's hold at 13.1v when full and rested.

A trickle charger is intended to keep the bank from self discharging, not keep the bank from self discharging AND run a 50 ah load daily. This is the most likely culprit. Your batteries have been undercharged long term and now suffer from progressive capacity loss.

You might try replacing the BlueSkies with the Morningstar controller if you still have it. I know that the Blueskies gets the thumbs up from a number of people but I have dealt with a few people unhappy with them. Even if the BlueSkies is good there is a massive difference between 420 watts of solar and 3.5a of trickle charge.

So how to check your bank without a lot og fancy gear. Get the rig into the sun for a few days and let the solar do it's thing without loads. Once well charged disconnect the batteries and separate them. Let them rest for 24 hours and check the voltage to see if one or more are lower. Next put a good sized load on each of the batteries and see if it drops the voltage faster than on the other two. Then hook each up to the solar in good light and see if the voltage climbs faster on one or more than the other batteries. A bad battery loses and gains voltage faster than a good one. You could try running a equalization charge on each to see if it helps.

The last thing is at 3 years old your batteries have seen close to a thousand cycles. Even if they are not full cycles, they are still cycles and your batteries have some age to them. Older batteries are subject to abuse much more so than new ones. Undercharging them for 5 weeks likely did a real number on them. I had a 5 year old starting battery that was great day to day until one day the truck would not start and we cranked it over until we needed a jump start. After that it would not take a charge. It was killed by a event that would not have mattered when it was new.

 

[WalkaboutTed]

Okey dokey, thank you all. I'll start with the easy stuff first. I don't have a lot of time until this weekend to do much else. I took off the charger, turned off the fridge, moved it into full sun and see what I get. Yes, (to Jim) I still have the Morningstar in storage. I figured that you and I might cross paths one day and I could give you that and a bunch of leftover wiring stuff. It's not a full 420 watts at one time since I have one panel on the side. At elevation last week, the side panel on the other van was proportionately outproducng the overhead panels by 8 times, but by midday, it's maybe putting out 50-70 watts, max. The other panels then pick up the slack.

Regardless of whether the batteries are toast or not, I don't need to, nor can I really afford to replace the whole bank for now. We'll just have to see what happens. I guess #4 son gets a the trickle charger. I have the 25amp CTEK charger that will equalize a battery if I determine that it needs to be done. It was nice to have the extra fridge, though, for when I'm boondocking alone with the trailer and I don't want to go into town for a few weeks.

Something interesting, I don't know if it means anything, but right after I disconnected the trickle charger, the voltage on the charge controller is 14.2v while the voltmeter directly on the batteries reads 13.4v. What would that mean? Thanks,
Ted

 

[jimindenver]

That means that the cables between the charge controller are too weak for the controller to read the voltage properly. The Morningstar will have a voltage sense line to correct this but with that big of a difference you really need fatter wires OR a shorter distance between them. There could be a bad connection or corrosion on the terminal/cable creating the issue.

and

if either it is under cabled or has a bad connection/corrosion the controller THINKS it is charging the batteries but is not actually charging them.

 

[XERTYX]

I have seen some people testing multiple charge controllers and reviewing them. A large number of them were inaccurately displaying the voltages. It was pretty surprising. The first thing I think I would do is test the batteries with another volt meter. If the charge controller still shows a higher voltage than the volt meter that's your answer. The controller thought they were full. The trickle charger couldnt keep up with the load just like jim said.

Secondly I'd follow the trouble shooting advise and try the other controller. Maybe they arent toast. Or only 1 or 2 of them are toast.

 

[Elbear1]

Controllers show what theyre putting out not what the battery is at. With charge time the 2 will be equal. At least thats how mine is.

 

[jimindenver]

Noooooooo

I have never had a controller that showed differently than the bank voltage, if they did there was a issue somewhere, especially the difference seen by the OP. Then again I have only handled a few charge controllers over the years.

 

[B and C]

My charge controller will show both panel volts and battery volts depending on the current setting.

 

[Elbear1]

Noooooooo

I have never had a controller that showed differently than the bank voltage, if they did there was a issue somewhere, especially the difference seen by the OP. Then again I have only handled a few charge controllers over the years.

Mmmm...

My converter outputs 14.7v constant. If the bank is drained it takes hours for the bank to match. That big of a discrepancy is likely whats being seen.

 

[jimindenver]

your converter is what charges the batteries while on shore power or a generator. A charge controller has to be able to read the banks voltage to know when to change modes.

 

[Elbear1]

your converter is what charges the batteries while on shore power or a generator. A charge controller has to be able to read the banks voltage to know when to change modes.

Even when its it 3 stage mode it does the same. All chargers and batteries will have a big gap in a constant voltage mode when theyre low. Maybe his controller displays output voltage...like I wish mine did.

 

[jonyjoe303]

I rarely see it mentioned but voltage drop on 12 volt system is always a big problem. That what kill my agm battery. I was float charging my battery for years, solar controller read 14.4 volts, the battery terminals were reading 13.9 volts. If you don't use your battery too much you will never realize you been undercharging your batteries. When you do put a big load on it, drain it more than normal, thats when you will find the battery has lost capacity. I never checked voltage at battery terminals, why would I, the solar controller showed me the voltage even though it was wrong.

To compensate you need to raise the charge controller bulk setting to a higher setting. Now that I'm using lifepo4, I have the bulk setting set at 15.5 volts (as high as it will go) and I barely can get a full charge 14.6 volts. With lifepo4 there is no guessing if the battery is fully charged, the bms will trip if the voltage climbs to 14.6 volts and it rarely does. With lead acid when they start losing capacity they start to charge quickly to 14.4 volts. I figure my lead acid was fully charged since it was in float mode 13.6 volts (with voltage drop maybe 13 volts).

Since your battery is mainly getting charge by your charge controller, that were you have to fix it. Depending on the distance from controller to the battery it might not be economical to use bigger gauge wire which may or may not fix the voltage drop, it didn't fix it for me. Raising bulk voltage is an easy fix. At least for your next batteries you will know what to look out for.

 

[regis101]

Before the sun came up I looked at the LCD on the Rover 20a and took a battery reading with the VOM.
No load(s) during the night except for the controller itself. 12.7 and 12.8 respectively. Two 55a AGM's for this small system.

 

[WalkaboutTed]

MYSTERY SOLVED!
I turned off the solar panels to the batteries last night and this morning the resting voltage looked good (12.7v). I stated going through my diagnostics, everything looked as expected. The voltages on the batteries were all in range with each other. No corrosion, wires all tight, batteries looked and felt normal. I reset the charge controller to the defaults and then to the recommended parameters of my batteries.

I then turned on the solar panels and stated measuring the output of the panels, vs the batteries. I noticed slight whiffs of sulfur odor. I ignored it as there are dumps stations and RV holding tanks in the area. And I dumped the tanks yesterday. I have a very sensitive nose and I couldn't smell anything specifically associated with the batteries.

But then I felt the batteries. Battery #2 was quite warm to the touch! The others were cool as cucumbers. In just the hour or so since I turned the solar back on, that bad battery had heated up quite a bit.

So, I turned off the solar panels again and will pull out the battery when it cools down. I don't know how damaged the other batteries are, but even weakened, hopefully they'll be able to run the fan and charge USB electronics. I'll update with the rest of the story for those who are interested.

Maybe my leaving them on the charger or running the fridge contributed to the battery 's demise, or it just died an el cheapo death, we'll never know. That's life.

Thanks to all of you for your help!
Ted