Battery's dying to fast

[greenkarson]

I've got to admit I don't know a whole lot about batteries

Here is my situation I have two D8 size agm batteries rated for 200amp/hours each. They've worked great for the last 4 years at my remote cabin. But this last weekend. Even with the turbine putting a consistent 2amps into them I can only run a 100watts for about 3-5 hours before the inverter cuts out from low voltage. I'm only at the cabin 1-2 weekends a month but the batteries are always kept charged with the turbine and solar. Are my batteries done for? They haven't been abused just seams like they went from being good to bad real fast. I'm not on that location now it's about 1.5hour drive. But I've been wondering could it be corroded terminals?
Thanks for any info

[Flux]

Not sure what a D8 size battery is, but if things have changed suddenly there may be a fault in one of them. If they are in parallel and one has dropped a cell it will discharge the good one. If they are in series and one drops a cell the bank will overcharge the other cells and dry them out.

The only real way is to check individually. At 4 years I suspect they are near end of life.

Flux

[greenkarson]

Here is a link to the batteries I have. http://www.lifelinebatteries.com/marineflyer.php?id=7 I would have no where near the amount of cycles that they are rated for

[Flux]

Not sure whether you are running 12 or 24v but I still suggest you test each unit on its own, Yes of course it could be a connection problem, you may be lucky looking for volt drops across the connections with a meter.

Looks to be a good grade battery but age is a killer as well as number of cycles of discharge. If you use them they wear out, if just left on float they eventually die, can't win with batteries.

See what you can find out next time you are there, may have a better idea of things to try with more information.

Flux

[greenkarson]

Thanks for the info
I'm running 12v. Not being on site is killing me. I'm wanting to work on it but I'm stuck here at home for a few days.

[dnix71]

What voltage is your inverter set to cut out at? 100 amp draw for hours at a time is harsh even for batteries that size. It you run them dead they won't last long.

If your inverter cuts off at 10.5 to 11v you have abused the batteries. 10.5v is stone cold dead. At that voltage you would be lucky not to reverse a cell when discharging at a high rate.

Set your cutoff at 12v and your batteries will last a lot longer.

Also agm's don't last as long as flooded batteries of the same type. 4 years is a decent age for an agm. Just floating the battery each day waiting to use them would age them some, esp. if you don't keep the batteries warm in the winter and cool in the summer. A cabin in the woods isn't going to have a nice stable temp inside.

[kitestrings]

Does your cabin have steady loads when you're away - like refrigeration, heating or cooling fans/circulators, parasitic loads - or is it only when you're there? Is the cabin subject to freezing or hot temps?  How long do they sit idle between visits?  All can affect longevity. ~ks

[Mary B]

Look for corroded wires too, they can cause bad voltage drops and under charging of the battery. I had a bad jumper on one bank a year ago and that was the exact symptom. One of my soldered ends had corroded and when I bent it the wire broke off. It had corroded through. That is when I went to lead covered copper straps for battery links. Got them from a friend who had worked in the telephone industry, he scrapped out  a large microwave site and these were on the battery backup bank.

[greenkarson]

Went back to the cabin to wire the inverter to restart when batteries where fully charged (see other post in controls) when I arrived all was well the inverter was in fault mode because the solar panel had been snowed in. But they had melted off and the turbine was working.  batteries where back up to 14v and the dump load heater element was hot.

So disconnected the inverter and replaced the switch with the relay. Everything still fine. The inline volt meter was still at 14.1v and c40 was in dump mode.

Then everything went bad! My cheap inline volt meter flickered then started burning. I quickly unhooked it. And used my multimeter to check the buss bars where the voltmeter was connected. The batteries where up to 18v and climbing. There was only the turbine running making 1amp.

The dump load mode was off heater was cold. But the batteries where steadily climbing to over 19v so I disconnected the turbine and hooked up a 12v 50watt lightbulb. To try to get the batteries down to 14. I could only get the batteries down to 17.5 volts. So I separated the two batteries. Both batteries where above 18v. And not going down at all.

So a couple questions I'm assuming there is some sort of a short in the batteries. But what the chance of both batteries shorting at the exact same time to the exact same voltage?  And why doesn't the c40 stay in dump mode at 17v plus?

I'm assuming a shorted agm battery is done for?  If they are I guess I'm out of the renewable energy game for awhile.

[dnix71]

For the batteries to stay high like that means the solar panels were still connected somewhere. Your AGM's may be okay as long as the vents didn't pop. If they vented, they are dead.

I have pull fuses inline with both sides of my panels and 2 controllers. Pull the panel sides first and if necessary, pull the battery sides. That absolutely disconnects everything. Reconnect the battery side first and then the panel side and wait for the controllers to boot up.

[greenkarson]

No the solar was not connected. Plus it was in the middle of another snow storm the panel weren't producing anything. And the turbine was only putting out 1amp. And when I separated the batteries they where total disconnected from everything.

Any other ideas?

[dnix71]

Don't let them sit that high. I know of no real lead acid 12v battery that would ever read 19v disconnected. There must be something wrong with your backup meter, like a bad probe cable or dying internal battery.

After sitting disconnected for a day, make sure they have warmed up to at least to 50F and check the voltage again with a known good meter. Check the vents, too.

If the vents are intact and the voltage normal, then use them again. You shouldn't leave a mill connected when you aren't there. Solar and a controller won't over charge. With the mill if there is no dump it will run away and you'll lose it all.

[greenkarson]

I actually tried 2 differnt multimeters with the same result. With the batteries separated and disconnected from everything. I hooked a 50watt 12v bulb straight to one of them. And could only draw it down to 17v. Unless by some rare chance both multimeters where wrong but that seams very unlikely. But it would explain why the c40 never went into dump mode and the inverter still worked

[OperaHouse]

I don't think any 12V lamp would last very long at over 17V.  That may be a reality check.    The C-40, if I remember right, doesn't care what  battery voltage is used.  It selects whatever voltage seems appropriate.  It may be thinking that  it is supposed to be operating at 24V.    Another possibility is that it could be shorted and that it has just floated to near the panels power point, the batteries being very sulfated.   I've seen some pretty high voltages on old batteries at not that high a current.   Did you actually measure battery voltage on the battery when it was removed from the system?

[joestue]

rip those vents off and add an equal amount of water to all the cells.

i'm thinking 300ml per cell would be a good start.

[Flux]

I think you have a measurement problem. Yes it does seem unlikely that both meters could be wrong and read similar but although you can over charge a 12v battery to up to 19v, when you take it off charge and load it with 50W it will come down to 14v in a few seconds as the surface charge comes off.

Most likely the C40 isn't dumping because it is really below 14v.

Check the meter or get another and start having a good look. Either both meters are wrong or you are not measuring what you think you are. Sometimes in a situation like this it takes a while to get to grips with what is really happening, just go through it methodically and don't take things at face value.

The surest guide is that a 12v battery being discharged at 50W will be below 13v in less than a minute as the surface charge is dissipated. Check your meter on the car battery if you have no other means. 14v engine running dropping to 12.6 with engine off and lights on, if meter is wrong abandon testing until you sort it.

I wouldn't worry about battery state until you sort voltage readings.
Flux

[greenkarson]

I just went to test the meter on the truck battery. One of The meters battery was dead. I'd left it on and in the truck at -10c all night. Changed the battery. The truck battery tested as it should with both testers. So now I'm going nuts not being on site to test the batteries again. A couple more questions. Would -14c effect a multimeter volt reading?  Like was all ready pointed out. Inverter never cut out at high voltage. I've seen it cut out at 15v in the past. And the c40 never went into dump mode. And the bulb worked fine. 

And I thought you can't add water to a agm battery?

[Flux]

Unless the meter is built with military spec ICs I wouldn't trust its readings below 0C. If it reads sensibly on your truck battery at -14C it may be ok.

AGM are designed to be sealed for life and if not over charged and are treated properly that should be it.

Some venting does often occur in less than ideal conditions which looses water. Some people when faced with cells not performing manage to inject water and get more life out of them. At this point I would not do this but if your tests do indicate loss of capacity then there is nothing to loose by trying. Some go as far as adding excess water so that they behave as flooded cells. All AGMs I have had have failed for other reasons so I am not going to comment.

Flux

[dnix71]

I'm with Flux on low temps affecting your readings. Normal consumer electronics don't work correctly at -14C (7F). -18C is considered safe for long term storage of frozen food in the US.  Leave your camera out in those temps and it won't work at all. Batteries are affected by temps that low, too.

If the inside of your cabin gets that cold, you can't trust the controller to work correctly, either. You need to either find a way to keep you battery bank and electronics warm or else disconnect it all when it gets cold like that.

If the air warms up too fast you will get condensation on unsealed electronics.

[joestue]

condensation inside the meter may screw with the readings as well.

have the batteries lost capacity because they are cold?


how these AGM batteries recover the water lost during overcharge is simply that the fiberglass isn't saturated with electrolyte, and the hydrogen and oxygen can migrate through the mat and reach the other electrode, where they react with the plate. this is a process that doesn't work if you push too much current into the battery.
Here's an example: at 3 amps, pushing 35 amps hours worth of overcharge into a 35 amp hour cell was sufficient to raise the float voltage 100mv, due to the acid concentration increase. brand new batteries too.. i added 35 amp hours worth of water (i forget how many cc's that is) and the voltage dropped back down.

[greenkarson]

Of coarse I can only speculate until I get back there later this week. The suspense is killing me.

 The charge controller and battery's and inverter are all in a unheated shed. With a ac line running to the cabin. They have worked fine for about 5 years. There is a few weeks every winter that it doesn't get warmer then -25°c. And everything is kept to the proper voltage by the controller.

If I'd just used one multimeter I'd be more convinced it was the problem.  but for two meters to give consistent readings over the period of a hour. I'm baffled but who knows

[dnix71]

Fully charged Yellow Top Optima's will freeze at -30F (-35C). If the temps in the unheated shed are below -25C for weeks at a time your batteries have probably partially frozen. Lead acid batteries don't work well at temps like that. You would be better off taking them somewhere warmer before the cold season or else insulating them heavily and using the solar and mill to keep them warm.

If you are trying to measure capacity in cold weather like that, forget about it. Capacity falls about 1% per degree C below 20C. At -25C you have only 55% of rated capacity based on temperature alone.

[OperaHouse]

Where is it that it doesn't get warmer than -25C for weeks and why would you want to go there?

[greenkarson]

I'm here in Ontario canada. I've attached a picture of my truck dash from last winter. And a summer picture of the cabin. Just for a little visual aid. Ha

[electrondady1]

loving it.
https://www.youtube.com/watch?feature=player_detailpage&v=JstZIsrGlP8

[greenkarson]

First let me apologize to anyone that was losing sleep waiting for me to reply with the results. Haha. Ended up selling our house faster then expected and had to move right away. Never had time to go back to cabin. But anyway. I'm back at the cabin this weekend

Armed with fresh batteries in the multimeter. The batteries both where around 13 volts. Hooked everything up. Everything is working fine.

So I have 2 theorys on what happened.

First theory: is that a loose wire  between the battery and the charge controller was letting the batteries over charge. When I was installing the relay I tightened the wire which then burnt out the inline voltage gauge. And the batteries cam back down to normal voltage while I was gone

Second theory: the planets all aligned.  and the inline voltage meter burnt out and the two differnt multimeters gave consistent  but inaccurate readings.

Either way will now never know. And it will be discussed threw the eons of time along with how the pyramids where built