Strange deep cycle storage results?

[Rich Stidger]

So here is the deal-

Prior to this past winter storage of 2013 to 2014 I have always removed my four deep cycle house batteries (golf carts US Battery model 2200 232 AH), brought them home and fully charged them and then kept them on a float charge over the winter.

So this year after reading that MaineSail and others fully charge and equalize their batteries, completely disconnect them, and leave on-board over the winter, I decided to do an experiment. I brought them home, fully charged and equalized and left them disconnected in my cold unheated garage. And I checked them a couple times through the winter. I figured that if I saw them discharging to any significant degree, then I could just charge them and dismiss the idea of leaving them on-board over the winter.

They started out between 6.38-6.40V at the start of the winter- about October 20th. By March 24 they were 6.27-6.31V, and today they were 6.24 to 6.27V. So they had an average voltage loss of about 130mv over the winter. Based upon 12V, that is 260mv loss or just over 1/4 volt. The loss seemed a bit higher than others had reported, but I'm going by my memory on that.

The real surprise was that out of 12 cells in the four 6V batteries, 9 cells had lowered levels of electrolyte. These 9 cells were just barely covered at the top of the plates. So where did the battery acid go to? The 3 cells that were covered had about 1/8- 3/16" over the plates which I think is about where they were in the fall.

Today I also took specific gravity readings of all the cells using a refractometer type gauge. Since it uses just 3 drops of liquid, I was able to get a sample from the 9 cells that were very low. The readings were all between 1.240 and 1.251 corresponding to 86% to 94% charged.

I am generally unhappy and concerned about the overall health of these 3 year old batteries. I'm wondering if I have allowed sulfation to occur on the batteries that were sitting at only 86% for several months.

Anyone have any comments and especially any idea as to why the electrolyte became low in 9 of the 12 cells?

 

[Maine Sail]

So here is the deal-

Prior to this past winter storage of 2013 to 2014 I have always removed my four deep cycle house batteries (golf carts US Battery model 2200 232 AH), brought them home and fully charged them and then kept them on a float charge over the winter.

So this year after reading that MaineSail and others fully charge and equalize their batteries, completely disconnect them, and leave on-board over the winter, I decided to do an experiment. I brought them home, fully charged and equalized and left them disconnected in my cold unheated garage. And I checked them a couple times through the winter. I figured that if I saw them discharging to any significant degree, then I could just charge them and dismiss the idea of leaving them on-board over the winter.

They started out between 6.38-6.40V at the start of the winter- about October 20th. By March 24 they were 6.27-6.31V, and today they were 6.24 to 6.27V. So they had an average voltage loss of about 130mv over the winter. Based upon 12V, that is 260mv loss or just over 1/4 volt. The loss seemed a bit higher than others had reported, but I'm going by my memory on that.

The real surprise was that out of 12 cells in the four 6V batteries, 9 cells had lowered levels of electrolyte. These 9 cells were just barely covered at the top of the plates. So where did the battery acid go to? The 3 cells that were covered had about 1/8- 3/16" over the plates which I think is about where they were in the fall.

Today I also took specific gravity readings of all the cells using a refractometer type gauge. Since it uses just 3 drops of liquid, I was able to get a sample from the 9 cells that were very low. The readings were all between 1.240 and 1.251 corresponding to 86% to 94% charged.

I am generally unhappy and concerned about the overall health of these 3 year old batteries. I'm wondering if I have allowed sulfation to occur on the batteries that were sitting at only 86% for several months.

Anyone have any comments and especially any idea as to why the electrolyte became low in 9 of the 12 cells?

Anything over about 6.34-6.36 on a US Battery is a surface charge.. In cold temps a surface charge can hold on for multiple weeks but it is still not real capacity or a voltage that is useful.. So on the healthy batts you only lost .08V to .09V in SIX MONTHS! That is pretty darn good.

How are they wired on board?

What is your normal absorption volgage?

How long is the absorption time before float?

Hose often do you check electrolyte?

We're the batteries equalized or fully charged before being put into service?

What was the net accepted current at 15.5V or more?

How long did you EQ for?

Did resting SG line up after EQ?

What was the temp of the batts when equalized?

If the case temp was below 77F did you temp compensate EQ voltage?

 

[centerline]

I have a comment. im sure it cant answer your questions, but it will give you something to read until something better gets posted EDIT: by the time i posted, something better has came along... sorry.

i deal with batteries all the time. a lot of batteries, but not in any scientific manner like some do. I test and replace for customers that dont care why there is a failure, but how fast can they get back up and running. downtime is much more expensive than batteries in some cases.
so some others will be able to dissect your problem better than i can.

this is only a thought that passed thru my mind as to why you are seeing what you are seeing in the voltage levels....
where you used to keep them charged all winter, depending on the charger you used, it could have caused some minor damage or sulfation during that time...yet never noticed the slight difference because they were always on the charger.
NOW, while you are trying to store them without the support of the charger, you could be seeing the results of the slight damage that may have been caused previously...
its not common for a battery to show the damage being done to it, immediately. it almost always shows the ugliness at a much later date...

But still, whether there is any slight damage or not, they still seem to be well within the definition of good usable batteries...

as for the electrolyte levels, while a battery is charging or after it has recently been removed from a charging source, the electrolyte levels will be higher in the cell... as the cells cool, the water absorbs into the plates and "condenses" to a lower level in the cell. so could it be possible that this is the issue your having?
I can think of no other earthly way for a dormant battery to lose liquid from the cell other than a visible leak or evaporation, which is highly unusual for a dormant battery to have that amount of evaporation, even over several years time.