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Author Topic: Stratification in Lead Acid Batteries  (Read 740 times)
AA6P
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« on: May 18, 2019, 10:43:59 AM »

An Internet search turns up quite a bit of information on stratification in lead acid batteries. Does anyone know how long it might take to see this condition if storing a car for several months and using a trickle charger?

It sounds like stratification can result from overcharge or the effects of simple gravity if the battery sits unused long enough.
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K5LXP
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« Reply #1 on: May 20, 2019, 04:25:47 AM »


Just sitting it is stratifying.  Physical movement will stir it up, say motion received in a car that's driven.  Equalization and subsequent gassing will also stir things up, float charging with a maintainer won't do that.  A few months wouldn't concern me too much, it takes a lot longer than that for the damage to become evident.  Sitting that long will also require a few cycles to recover all the usable Ah.  Since lead acid batteries go bad over time no matter what, I would consider an equalization cycle every couple of months to be a worthwhile exercise to keep the battery active.

Mark K5LXP
Albuquerque, NM
 
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AA6P
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« Reply #2 on: May 21, 2019, 03:41:42 PM »

An equalizing charge done every few months does sound like an excellent idea. The CTEK chargers have that capability with their Recondition Mode. The CTEK MXS 5.0 provides a maximum of 15.8 volts at 1.8 amps in that mode.

The articles on stratification mention something quite interesting. The chemical reactions in a lead acid battery for discharging and charging involve both the creation of water and the loss of water.

To possibly minimize stratification, I had the thought that a three stage charger on a timer might be a better choice than using a trickle charger. It could be set up to charge for some length of time on a regular schedule. My CTEK charger at 4.3 amps seems to leave a trace of moisture around the vent caps so maybe there is some motion in the electrolyte.

The mention of stratification also brings up a related question. I wonder if the specific gravity in the cells immediately after charging is higher in the lower portions of each cell. If so, specific gravity measurements at the top of each cell might not be accurate until some period of time has elapsed. I have noticed that specific gravity measurements are not accurate for a period of time after adding water to a battery.

Thanks for the reply.
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K5LXP
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« Reply #3 on: May 21, 2019, 07:39:00 PM »

There is a diffusion mechanism with regards to electrolyte specific gravity.  It's fairly standard practice to allow a battery to sit for 24 hours to get an accurate SG measurement.  Terminal voltage the same thing.  Temperature factors into both as well and there are correlation tables for that.  Some battery purists might argue that frequent equalization charges will be hard on the battery and will use water, which is true to some extent.  So would be the effects of sitting at some state of discharge, namely stratification and sulfation.  So take your pick, keep it equalized and useable and add water once in a while, or let it slowly degrade to eventual uselessness.   

In some correspondence with an engineer at US Battery he described the stratification process as taking "weeks" and I suspect it's a slow gradual process.  So hard to say just what the interval should be between equalize cycles.  Technically it won't need it for charge replenishment, just for agitation and references I have cite a cycle interval and not storage.  Stratification is a common issue with the solar power folks, maybe you might find some specific advice there.  My vote would be to do it once a month but absent data, that's a guess.  Would be a good opportunity to check water at the same time whatever interval you pick. 

Mark K5LXP
Albuquerque, NM
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AA6P
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« Reply #4 on: May 22, 2019, 02:57:56 PM »

Thanks for the help Mark. I was aware of the 24 hour waiting period for voltage measurements but hadn't thought about it for specific gravity. It looks like voltage measurement comparisons should really be done at no load. Opening a car door with a fairly low current drain can drop the battery terminal voltage a few tenths of a volt.

Internet searches on lead acid batteries always turn up a lot of information from the solar power users. There is a lot of expertise in those forums and I've learned quite a bit.

Last month at the W6TRW swap meet I learned that Edison Nickel Iron batteries are also being used. Those batteries apparently work for decades or even longer. That long life would really have been terrific had those batteries worked for automotive applications! Smiley
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K5LXP
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« Reply #5 on: May 22, 2019, 08:32:43 PM »

Opening a car door with a fairly low current drain can drop the battery terminal voltage a few tenths of a volt.

For storage I would disconnect the negative lead from the car.  This is the only way to know for sure a parasitic load won't cause an issue.

Quote
always turn up a lot of information from the solar power users.

Yep, if there's an advantage to be gained, the solar guys have rooted it out. 

Quote
I learned that Edison Nickel Iron batteries are also being used.

I haven't looked at those in a while, in years past they weren't the greatest efficiency wise.  But you're right, from what I understand they can be rejuvinated by replacing the electrolyte.   In my collection of stuff I have an antique Edison Battery Oil bottle, which is an oil you'd put into the cells of NiFe batteries back in the day.  I know they were used in rail applications because they were very durable and long lived.  I know a number of years ago there were companies making NiFe batteries in BCI sizes and had improved the efficiencies a bit but I haven't followed up on that.  Guessing with the advent of lithium there may not be much call for NiFe in consumer grade sizes.  I have a feeling that as the $/Ah of lithium ratchets ever lower we may see a shift away from lead acid too.  Look at how quickly LED's have supplanted other forms of lighting, once that scale tips things can change in a hurry.

Mark K5LXP
Albuquerque, NM
 
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AA6P
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« Reply #6 on: May 23, 2019, 11:18:01 AM »

I was just reminded that AGM batteries do not have a problem with stratification although the extra cost may not be justified. I've also wondered if my car would charge an AGM battery adequately as it does not have a smart charging system and it is also very light on charging.

Some of the early Electric Cars used the Edison Nickel Iron battery.

https://www.livescience.com/21227-edison-electric-car-battery.html

Here is one of the companies producing Nickel Iron batteries today for the solar power industry. The battery banks are quite large with each cell producing only 1.2 volts.

https://ironedison.com/nickel-iron-ni-fe-battery

The Edison Battery Oil Bottle in your collection sounds like a nice piece of history.

http://www.antiquebottles.com/edison/
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K5LXP
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« Reply #7 on: May 23, 2019, 07:47:54 PM »

Notably absent in that web link is the charge efficiency.  Something tells me that's one hurdle that hasn't been overcome.

The ones I'm thinking of I can't seem to find so I'm guessing they didn't make it.  There were like a standard group 24 or 27 size and had some attraction with their cycle life, efficiency notwithstanding.

Saw the bottle at a fleamarket and when I saw edison on it I figured it was worth a few bucks as a novelty.  I don't think they're particularly rare or valuable but it's fun to have on display in the hamshack.

Mark K5LXP
Albuquerque, NM
 
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AA6P
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« Reply #8 on: May 25, 2019, 11:46:19 AM »

The ones I'm thinking of I can't seem to find so I'm guessing they didn't make it.

I found some information on a Nickel Iron battery made by Eagle-Picher. It was compatible with BCI Group GC-2 and might be the battery you remembered. The specifications look quite good for certain applications. If you download the document you may need to try an alternate pdf reader.

https://www.nickel-iron-battery.com/eagle-picher.pdf

The link is available on the site below along with a lot of very interesting information. There is also a link to Bulletin 850X published by the Edison Storage Battery Company in 1914.

https://www.nickel-iron-battery.com/

The Wikipedia page on the Nickel Iron battery shows the charge/discharge efficiency at something less than 65%. Lead Acid batteries are apparently in the range of 85%.

It would be great if improvements can be made to the basic Nickel Iron battery cell. The original batteries required a lot of maintenance and also produced a lot of hydrogen gas. Undecided
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K5LXP
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« Reply #9 on: May 26, 2019, 08:30:29 AM »

I'd have to go back into my archives (20 years ago or more) to see if I could find it but the weren't golf cart size, more automotive like a group 24.  They were from a startup and I'm guessing they couldn't overcome the technical hurdles that this chemistry presents.  It would be interesting to learn just what efficiency the iron edison cells have and I find it curious that it's not mentioned considering the solar market they're targeting.  The sure do have great appeal from the simplicity standpoint for stationary applications. 

Mark K5LXP
Albuquerque, NM
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M0GVZ
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« Reply #10 on: May 27, 2019, 10:52:38 AM »

A few months wouldn't concern me too much, it takes a lot longer than that for the damage to become evident.

Can confirm. I have a convertible that sits in my garage unused over winter. I've had it 5 years now and never noticed any issue.
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AA6P
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« Reply #11 on: May 28, 2019, 12:39:08 PM »

They were from a startup and I'm guessing they couldn't overcome the technical hurdles that this chemistry presents.  It would be interesting to learn just what efficiency the iron edison cells have and I find it curious that it's not mentioned considering the solar market they're targeting.

I would have been very interested in any CCA Ratings. I don't believe Nickel Iron batteries provide the high starting currents available from lead acid batteries.

I've seen a number of references that work continues on the Nickel Iron battery. Let's hope significant improvements will result.

I did find several interesting discussions on Nickel Iron battery efficiency in the solar power forums. Here is one very informative thread.

https://permies.com/t/93220/Nickel-Iron

Yesterday I watched a very interesting YouTube video with Jay Leno and his 1909 Baker Electric. The car used Edison batteries and had a range of 80 miles. The video shows one of the original Edison batteries and a photo of the charging stations available at the time. The vehicle has been fully restored other than the Edison batteries which have been replaced with twelve 6 volt deep cycle batteries. The Edison batteries appeared to have five cells wired in series.

https://www.youtube.com/watch?v=OhnjMdzGusc

Thanks M0GVZ for the reply and I assume you use a trickle charger or battery tender. I was surprised to learn that there are different opinions on the best way to maintain a battery. Trickle charging can result in overcharge if the float voltage is too high or temperature compensation is not used. CTEK chargers have a float mode that runs for a maximum of ten days. The battery voltage is then monitored and current pulses are used to maintain the battery as needed.
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LYFAN
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« Reply #12 on: June 01, 2019, 10:25:57 AM »

AGM can definitely be used in cars. VWG and Mazda have been using them for many years. I've used them for 20? years. All batteries are not equal and all automotive charging systems are not equal, but in general they will work as a drop-in replacement. If everything is done right they can have an 8 year life as opposed to 3-4 years if it isn't quite right, which may still be good enough for many drivers.

IIRC typically it takes 24 hours after a charge for electrolyte to redistribute and even out in a wet lead battery. And in as little as 30 days without a charge, some sulphites will precipitate out of wet lead, causing some permanent capacity loss. The usual arguments about trade secrets and specific compounds apply so your mileage will definitely vary.

Car charging systems are all over the map. Some will charge to 14.4-14.6 and then if the car is running at highway speed with light loads, actually shut down the alternator to get better mpg, and may not restart it until the battery voltage is sensed at 12.6 again. They are not just simple one or three stage chargers any more. Originally, they were designed to "not overcharge" a battery if the car was on the highway for eight hours or ten hours at a clip, so they never really were optimized to bring it up to 100% and leave it there, but more to not overcharge it. And again, many different charging schemes are out there. Like the children of Lake Woebegone [radioplay] they are ALL above average.
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AA6P
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« Reply #13 on: June 04, 2019, 04:27:19 PM »

And in as little as 30 days without a charge, some sulphites will precipitate out of wet lead, causing some permanent capacity loss. The usual arguments about trade secrets and specific compounds apply so your mileage will definitely vary.

Thanks for the comments on several interesting subjects. The note about 30 days without a charge sounds like good information. Optima Batteries mentions 12.4 volts as an important level that may be a similar calibration point.

https://www.optimabatteries.com/en-us/experience/2012/12/optima-mailbox-parasitic-draw-stored-vehicles

The article makes two other important points. The first is that alternators and charging systems today are often designed only to maintain batteries already close to full charge. The other point involves parasitic drain which can be a problem for vehicles not driven several times a week.

Measuring parasitic drain generally means disconnecting one of the battery leads which can result in loss of stored data. I may have found a way to estimate parasitic drain without removing battery connections. One of my small three stage chargers drops to about 13.1 volts when it goes from charge mode to float mode. Current measurements after the battery has drifted back down to 13.1 volts indicate a charge current of 20-30 milliamperes. The parasitic drain from the vehicle should be less than the indicated current. In the interest of safety, I used a digital meter configured for the ten ampere range. The current may read negative for a time after the charger switches from charge mode to float mode.
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