Issues with AGM vs flooded ...

lasitterlasitter 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.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    lasitter wrote: »
    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?

    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.
    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.

    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.
    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?

    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.
    Finally: What is the rule for the amount of power that AGM or flooded batteries consume just in keeping them "topped off" or exercised?

    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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lasitterlasitter Solar Expert Posts: 56 ✭✭
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,032 ✭✭✭✭✭
    lasitter wrote: »
    BB.: Thanks. Would you call BS on products like this? http://www.thermoil.com/golf-course-trades-magazine-thermoil-company-spotlight/


    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.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    My concern with the mist is it can damage nearby items in storage--Having a ventilated box of some sort keeps the mist (and some people are very sensitive to the rotten egg smell of sulfur) down. You can use a voltage controlled switch to turn on a fan when the battery voltage is a few tenths of a volt above your float voltage to vent the box.

    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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    BB. wrote: »
    I have read people that have mixed reviews of these caps (some like, others don't see that much reduction in water usage.

    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
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,013 admin
    Neat thing that vtmaps is saying--Gassing is easily replaced with distilled water.... Misting also is loss of sulfuric acid/electrolyte. Which weakens the electrolyte solution (we are warned not to refill cells with electrolyte, only distilled water).

    Mist/sulfur smell reduction is all good. Should reduce corrosion too of nearby connections and items in the room.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,032 ✭✭✭✭✭
    BB. wrote: »
    Neat thing that vtmaps is saying--Gassing is easily replaced with distilled water.... Misting also is loss of sulfuric acid/electrolyte. Which weakens the electrolyte solution (we are warned not to refill cells with electrolyte, only distilled water).

    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.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • ApplesApples Solar Expert Posts: 39 ✭✭
    Odyssey AGM are in a class by themselves, but the tuition is expensive. Should you be considering a premium battery, you may only equal, if that, their performance by choosing instead Lifeline brand AGM.

    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.
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