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AGM battery question  RSS feed

 
hrvoje bregovic
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Have a "Sole" AGM battery that went dead after 4 years of service. No particular stresses during its life. One of the cells is dead and a sudden drop is read after applying larger load. It worked in a 4 pcs. battery bank (to provide 12 and 48 volts). Anyway, it seemed to be really dry after trying to measure voltage on each of the cells. After adding water, the dead cell went from 0,13 V to 1,96 in about 40 minutes. I then poured 1 liter of dist. water in all the cells and let it be for a day. Today, not a single drop would come out of the battery after I turned it upside-down. Does that mean it would be wise to fill the other (good) batteries with some quantity to eventually avoid their defect ? Could lack of liquid be the cause of damage ? Thank you out there !  
 
Galen Young
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Location: out in the woods of Maine
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Contact the manufacturer ask they for the proper maintenance of your batteries.
 
hrvoje bregovic
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Galen Young wrote:Contact the manufacturer ask they for the proper maintenance of your batteries.
These batteries require no maintenance. Enjoy "out there in Maine" !
 
Galen Young
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A lot of new batteries are marketed as 'maintenance free'.

If you find yourself adding water, clearly your batteries require maintenance.



 
Troy Rhodes
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In your first post, you ask if you should add water to your batteries, and then in your next post you say they are maintenance free...it can't be both.



Note that AGM batteries do not normally have any liquid electrolyte, and adding water would almost never be a good idea.

I think you got good advice to contact the manufacturer.


Good luck, and I would like to know what you find out.


How far do you normally discharge your battery bank?

How was/is the battery bank monitored for depth of discharge?



Thanks in advance,

troy
 
hrvoje bregovic
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Troy Rhodes wrote:In your first post, you ask if you should add water to your batteries, and then in your next post you say they are maintenance free...it can't be both.



Note that AGM batteries do not normally have any liquid electrolyte, and adding water would almost never be a good idea.

I think you got good advice to contact the manufacturer.


Good luck, and I would like to know what you find out.


How far do you normally discharge your battery bank?  - only once to 11,8 in 5 years

How was/is the battery bank monitored for depth of discharge? - no monitoring: the inverters never cut-out due to deep discharge until the said batt. went dead.



Thanks in advance,

troy

Hello, Troy,
here are facts on AGM: Absorbed Glass Matte or "AGM" batteries are the latest and greatest in lead-acid batteries. An AGM battery uses a separator consisting of fiberglass between the plate and wrappers to hold the electrolyte in its place with capillary action. Combining the lead plates, electrolyte, and fiber glass separation fibers in a confined space, AGM batteries create a "physical bond" by way of capillary action. Similar to how water creeps up a towel when it is put in a bathtub. This capillary action holds the liquid inside the glass matting, making the AGM Battery "spill proof" if it is ever exposed.

Now, surely the matte cannot hold unlimited qty. of liquid, so I guess my question remains. Thank you.
 
Troy Rhodes
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I am keenly aware of how AGM batteries work.

Every time you use your battery bank, you discharge it.

I want to know HOW MUCH you discharge it in a typical 24 hour cycle.

How is your battery bank recharged?



Thanks in advance,

troy
 
hrvoje bregovic
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Hello Troy,
I'm not keeping track of what my discharge is. As said above, only once to 11,8 V three years ago. In the morning it's usually 12,2 - 12,25. The charging starts with morning light. The question of "where did the water go" remains. And, finally  - it's a VRLA type of batteries.
 
Troy Rhodes
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All lead acid batteries share certain charge characteristics.  VRLA AGM batteries are no exception.

During the charge cycle, hydrogen and oxygen are produced. In VRLA batteries, these gasses are allowed to build up pressure--to a point.  This allows the oxygen and hydrogen to recombine and form water.  That's what makes VRLA batteries "maintenace free".   If the charge rate, and discharge amount are not carefully regulated, the pressure build up exceeds safe pressures and the valve vents the excess pressure.

That's where your water went.

Either the discharge levels went too deep a few times, or the charge protocol that the inverter is using does not use an appropriate protocol for your particular AGM. 

If the charge rate is faster than optimal for your pack size/brand/type, this will cause outgassing and loss of water.

If it doesn't monitor battery temperature, it's not using a sophisticated charge protocol.  This will result in over or undercharging and shortened life.

If it doesn't have a very specific charge protocol for your specific brand of AGM VRLA battery chemistry, it's not using a smart protocol.

Here's a quote from a good battery page:

"Using normal target voltages to charge a battery that is colder than approximately 25ºC (77ºF) will result in an undercharged battery, which will deliver lower performance, reduced life and a higher life cycle cost. Applying normal target voltages to a battery that is hotter than 25ºC may result in an overcharged battery. This condition could lead to the drying out of VRLA battery cells. With flooded cells, the result will be excessive outgassing, increased battery maintenance in the form of more frequent watering and reduced battery life due to thermal stress. In fact, some battery manufacturers and charger manufacturers recommend not charging a battery that is 50ºC (122ºF) or hotter."

http://solarprofessional.com/articles/design-installation/understanding-and-optimizing-battery-temperature-compensation


I would highly recommend a state of charge meter for your battery pack:

http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge


This gives you another (and better) method to determine if you are charging or discharging too fast, too deep, proper equalizing, etc.


Another potential problem is if one battery gets hotter than the others, it will charge differently and fail sooner.  Periodic careful equalizing minimizes this effect. 
Sometimes the first or last battery in a string of batteries suffers more than the rest of the string.  Complicated...

 
hasan mohammadi
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I would appreciate anyone help me about following question: what is difference between agm separator for different application such as : solar, Ev, ups, motorcycle and start-stop?
 
Peter VanDerWal
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hasan mohammadi wrote:I would appreciate anyone help me about following question: what is difference between agm separator for different application such as : solar, Ev, ups, motorcycle and start-stop?


The separator is the same regardless of how you use it.
 
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