Issues with AGM vs flooded ...
lasitter
Solar Expert Posts: 56 ✭✭
My basement is over 30,000 cubic feet, so I'm wondering: With flooded batteries in this amount of space, what are the odds that gassing would ever really be a problem?
For a grid-tied system that experiences few outages and those generally being of short duration, I wonder about the necessity of giving up the capacity of flooded in favor of the lower maintenance and somewhat added safety of AGM.
If they're located indoors, is the maintenance on eight batteries (Trojan L16H 6V, 435Ah (20Hr) Flooded Lead Acid) really that hard to keep up with?
Finally: What is the rule for the amount of power that AGM or flooded batteries consume just in keeping them "topped off" or exercised?
Thanks.
For a grid-tied system that experiences few outages and those generally being of short duration, I wonder about the necessity of giving up the capacity of flooded in favor of the lower maintenance and somewhat added safety of AGM.
If they're located indoors, is the maintenance on eight batteries (Trojan L16H 6V, 435Ah (20Hr) Flooded Lead Acid) really that hard to keep up with?
Finally: What is the rule for the amount of power that AGM or flooded batteries consume just in keeping them "topped off" or exercised?
Thanks.
Comments
I will leave it to somebody that knows more than me about the required--But I would be concerned too about the electrolyte mist from charging/equalization.
AGM tend to have a bit shorter life than flooded cell of equal quality (from what I have read). No fumes during normal operation is certainly better. However--Remember that when AGM batteries are near their end of life (or you have a charge controller fail and over charge the AGM Bank), they still can out-gas hydrogen.
It probably depends on your personality... If leaning over and checking 24 battery cells, adding water, etc. once a month is something that you don't want to do--then AGM may be a better choice for you.
However, if this is your first try at off grid power--There is something to be said for saving 1/2 the price on batteries and being able to use a hydrometer to check the state of charge.
AGM's will use around 1/3 to 1/6th the amount of energy to "float" vs flooded cell.
Worst case (end of life, warm flooded cell batteries, fork lift type), you could be looking at 2% of battery bank capacity:
500 AH * 27 volts floating * 0.02 = 270 Watt*Hours per day = 0.27 kWH per day (worst case example)
Otherwise, you are probably looking at 0.1% or less for AGM in good shape (and less than 1% for flooded cell in good shape)--More or less educated guesses on my part.
-Bill
I would not be concerned with that space for liquid batteries. Every building inspector I have used wants the volume of space to equal an average north american single family dwelling's garage. Use the Trojans, it is so easy.
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Have good lighting (or use a head lamp) and space around/above the batteries to make it easier to service the battery bank. Having a cover of the batteries can help stray tools and children from getting at the terminals (the terminals on a large battery bank scare me more than working on 120/240 VAC circuits).
Regarding the oil in battery treatment. You do not see any battery mfg. put that stuff in new batteries (that I know of). And while it may help to keep the misting down, I would probably try for the water miser caps instead. By the way, there are three different height caps... NAWS lists the medium (I believe). I have read people that have mixed reviews of these caps (some like, others don't see that much reduction in water usage).
One thing that worried me about the oil--I wonder if it makes using a hydrometer almost impossible. It seems the oil would coat the inside of a hydrometer and make it about useless (???). And if there is one positive aspect of flooded cell lead acid batteries, it is the ability of using a hydrometer to measure the specific gravity and KNOW what your batteries are doing.
-Bill
I have the tall caps and do not see much reduction in water usage... most water loss comes from electrolysis (gassing) and evaporation of the water in the electrolyte. The caps do not recombine oxygen and hydrogen back into water. They may have a positive effect on loss by evaporation (water vapor may condense in the cap and drip back into the cell).
I have the tall water miser caps and can attest that the caps do reduce the mist and sulfur odor.
--vtMaps
Mist/sulfur smell reduction is all good. Should reduce corrosion too of nearby connections and items in the room.
-Bill
It is good to reduce it but I really have not seen this issue even with an 1,100 amp hour 48 volt battery system in a 62 Volt EQ. Overrated concern in a big room but I understand this is public and the lowest common denominator may be somebody so weird that I can't imagine it.
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If you have a few minutes: http://www.batteryplex.com/sheets/Od...n%20Manual.pdf
I have no interest in the company but I do use an Odyssey in my camp rig, recharged by a small off-grid solar power system and I am planning a small off-grid solar residential setup using a battery bank and larger inverter to power kitchen refrigeration. I chose an AGM due to the battery's location within the vehicle where venting a wet battery would be problematic. Happy I did. The Odyssey is a tremendous battery in many respects.