SLA (AGM) Battery Sulfation

[A J Coop]

Hello and hope the New Year is good to all.
I just recently had a frightening experience with my batteries!
So I thought it would be a good idea to share my fright.
I have The KID with 3X 12V 165Ah in parallel, LG 315W panel, 2.5KW inverter, CyberPower 3000 VA / 2700 W UPS.
On 10th of Jan 19 drawing 24A after the UPS finishes charging the current drops to around 18A, getting to the 2 hour mark, an annoying loud horrible buzzer sounded from the inverter? What the… Racing over to the KID, reading 10.3V @ 91% SOC 427Ah, scratching my head, I’d better lower the load, the voltage raised a little and I went back to work. Moments later BUZZZZZZZ, lowered the load again, voltage raised a little and went back to work in the dark (turned off the LEDs). One final buzz and the inverter went in to protection mode the voltage was too low, the UPS took over and started switching between inverter and UPS. Putting the UPS back in to the grid I noticed the kid reading 12.6V so I added a little load, (the LEDs) well the volts lowered to 10.5. This is bad my batteries are dead $1500 of batteries dead, going through my charge, float set points usage data I found that I was doing everything right with set points not deep cycling the batteries(80% SOC, 20% DOD), what’s going on!!! The batteries are 4 years old warranty is for another year, they have another 6 years of life..
A bit of a sleepless night, I remembered reading that if there is a serious voltage drop when load is applied means two things a battery/cell is bad or sulfation has occurred. So google been a good source of info I found that it may be sulfation.
Reading the KID manual and looking in this forum, I decided to bite the terminals and go for equalization of the batteries, acknowledging that equalization is more for flooded batteries, something had to be done.
Squeezed as much as I could out of the batteries and charged them, when float came about I started EQULIZE @ the absorb voltage, then let float for the remainder of the afternoon.
When the KID was in rest I recorded the day’s data and waited until there was very little light and switched to inverted power and crossed my fingers. Drawing 22.5A, 1 hour good, 2 hours good, then 4 hours later, 92% SOC 447Ah @ 12.6V. It worked the weight of $1500 lifted off my shoulders.
If this forum did not exist and Midnite Solar did not include Equalization in the controller the death of my batteries would have been, or a big expense rectifying the issue. I have in the past gone through three solar controllers (MADE IN CHINA) and none of them had EQ or anything like what is in the KID.
A big    THANK YOU    to MidNite Solar and this forum is in order.

[Westbranch]

here is a little reading for you. I have reread this several times and it is chock full of good info on SLA batteries and FLA's.

go here http://www.cdtechno.com/resource/support_doc.html

and  in the VRLA Batteries section.

click on the  the first document 41-2128 Charging Regulated VRLA Batteries

[ClassicCrazy]

"3X 12V 165Ah in parallel "

They probably are not sharing the charge and load evenly so that  could be why you are having problems with them.
Much better when they are all in series since then same current goes through each cell. Of course  you can't do that with 12v system.
With parallel the wiring has to be very well matched on each battery so the current is almost the same in each. And since the batteries themselves may not be matched too well in their internal resistance it makes it more challenging to get it all right  and have them share equally ( and charge equally) .

I have sealed lead acid batteries - gel type but called lead crystal. They are 2v cells so all in series . Supposedly this lead crystal battery technology they will never sulfate even if taken down to zero volts. Hopefully they live up to their claims for longevity because like you say batteries cost a pretty penny !

Larry

[boB]

One thing though about having the batteries in parallel, although there are 6 X 2V cells in each one, is that each battery sees the same voltage...  That can get off balance when too many are in series and worse when there are a lot of series/parallel batteries.

A good thing to have is a way to sense each batteries temperature or each batteries voltage under charge if temperature can't be looked at.  This can give a good idea of how well they are sharing and if one of the batteries are sulfated and more resistive than the others.  Having a lower amount of cells and all in parallel, you know that they are all getting the same voltage as best as you can.

AGMs can plump when you cook them I like to say, too.

Good thing you were able to get them going again !  That can be so scary when things like this happen.

boB

[ClassicCrazy]

Interesting thoughts on the series cells Bob . Guess I shouldn't be so lazy and get some voltage monitors on each cell and see what they are doing. I think it is Ross on forums here who does that .
I will have to investigate some of the options for monitoring voltage . And  temperature. The temperature part I would know how to easily do using DS18b20 one wire temperature sensors - can run them all in a single wire and since they are addressable can label each one as particular cell. I have 4 temp sensors outside monitoring fridge and freezer temps in the shed an displaying on LCD via arduino.
That much coding I can handle.

Larry

[boB]

Yes, checking individual cells is good IF possible.  Not a lot of batteries will let you do that though ?

What I like to do, and it's getting cheaper now, is to use a thermal imaging camera.  That way you can clearly SEE if there are any difference in cell temperature.  I have detected bad batteries, and especially AGMs this way.  But this was where several AGMs were in series.  In parallel, except for individual cells, the whole battery will at least have the same voltage applied as the others in parallel.  That's my take.

[ClassicCrazy]

We had a fire alarm system at work with 2x 12v  agm batteries in series . probably 33ah if I remember correctly . Every year they would fail the test of inspectors  - one battery would always have low voltage. It was in a warm location so maybe that was key to the problem. Seemed odd to me though that  just this panel compared to the many we had always had the failed cells. Of course these batteries were never cycled and just sat in float all the time so that didn't help anything either - plus I never trusted those battery analyzers that the inspectors used - attach and it supposedly told how many AH capacity they had.  Lower than certain percent and they failed the batteries so would have to put new ones on - once I had them check a new battery and that one didn't look too healthy either  according to their tester ! 

But yeah for those smaller type AGM you could feel them for heat or look for the bloat . No one cared how many times the batteries were replaced since the people replacing them didn't have to pay or them.

Larry

[RossW]

Guess I shouldn't be so lazy and get some voltage monitors on each cell and see what they are doing. I think it is Ross on forums here who does that .
I will have to investigate some of the options for monitoring voltage . And  temperature. The temperature part I would know how to easily do using DS18b20 one wire temperature sensors - can run them all in a single wire and since they are addressable can label each one as particular cell.

Yes, I make a modular monitor. Nominally 5mV/cell resolution.
They also take DS18B20 sensors, the boards will take one sensor per cell, so you can fully monitor voltage and temperature per cell if you wish.

[ClassicCrazy]

Do you have a place you market these boards Ross ?

Larry

[RossW]

Do you have a place you market these boards Ross ?

Not really, Larry. Mainly through word-of-mouth.
I'll send you a PM.

[A J Coop]

WOW
Thank you all.
As you all may know from past posts I am in Australia, the batteries are somewhat different to your batts, BUT batts are batts right *NOT*

More reading, Thanks Westbranch I've saved the page in my FAVs, read it after and until my eyes bleed.

ClassicCrazy; The issue of sharing.
I make a point to rotate my bank every 3 months, so the equilibrium between cells is achieved. I measure the Volts as soon as there separated, let the batts sit for an hour or so and measure again before putting them back. From memory there was a 0.05ish difference in 1 or 2 of the batts, if 1 batt is out it goes in the middle, if two, the middle and on the NEG side, I do that because the system is NEG potential! Whether it makes any difference??
When I purchased the batteries they were meant to be in “BANK” configuration.
The interesting thing is the only thing I got with the batts was Jumper Cables, the spec sheet, more to the point parameter sheet, nothing in relation to maintaining the maintenance free batteries! There was a lot of reading and guess work because each manufacturer is different, When I called the so called “Professional” battery supplier about the batteries marrying with the KID they were at a loss to answer my questions e.g. Absorb time, END AMPS, Rebulk,  temp. coeff. that of the batts (-30mV/C) and KID’s (-10mV/C) etc... HUMMM.
Hope your GEL batteries live to the expectation, pretty penny or golden penny!

boB; The sensation of that experience was heavy, more so when I did the EQ, cooking of the cells.
I had the BTS and a K-type thermo probe on the DMM realistically told me nothing of what was going on in the battery cells, there was no hissing, venting or boiling that I could hear.
As I said above rotate the batts for equilibrium weather is helps??
I understand cooking fries!
Thank you boB.

There is more to maintenance free batteries than the manufactures claim of maintenance free, why say maintenance free when really they need maintenance? Not even close to plug and play forget!

[ClassicCrazy]

The plug and play and forget is for places that have lots of $$ and don't have to worry about replacement if they only get half the life
expectancy claimed !

Larry

[A J Coop]

G'day Larry
Should have known, that pretty penny strikes again.

[Westbranch]

AJ,  PLEASE DON'T USE the EQ  term when talking about AGM or SLA or VRLA cells, as what you will find in that reading is that you go to the highest voltage for the cell and maybe a titch higher,  ... .1 or .2  V above that . A better term is Boost or Refresh charge. It is not meant to boil or drastically heat you AGMs...

Never expect most Battery Pro's to understand our jargon, most would not know what Absorb is, they have their own jargon and it based around "PLUG-IN " chargers, you know those 'smart chargers ' all the box stores sell...

enjoy the trip.

[A J Coop]

SORRY
I was going by what the manual stated and the function in the KID!
I honestly didn't think out side of the KID.
This is/was about the kid though, not out side the KID!

I understand...

I did enjoy the trip and fell over.
P.S.
I have not got around to reading your suggestion yet. I will do tonight, when I have time to my self.

I just finished having a quick read, a lot more detail than what I read in the past, and will correct how I explain things in the future, just as well, if I got it wrong I would have killed the batts. COSTLY
I will read it again and again to have it sink in, point taken. Thank you "HEAPS".

p.s.
It pays to do the extra mile in homework


Off to work, till then