Anyone with aerated electrolyte batteries? Higher efficiency, no equalize, longer life!

Graham Parkinson
Graham Parkinson Registered Users Posts: 167 ✭✭✭
in Off Grid Solar & Battery Systems #1
The usual problems experienced by those using RE batteries have all been dealt with before:
  • Stratification due to electrolyte differences caused by gravity settling dense electrolyte to bottom of cells
  • Sulphidation caused by differential chemistry
  • Positive plate corrosion caused by differential chemistry
  • Charge / Discharge inefficiencies by poor exposure of plates caused by non-uniform electrolyte
The typical small RE solution to the above issues is the application of overvoltage equalization which causes gas bubbles to form which stirs the electrolyte. A much more efficient way to make gas bubbles is to use a small aquarium pump requiring a few watts power. The pump feeds air into a manifold leading through plastic tubes to the bottom of each battery case. The pump can be run off the Charge Controller AUX out.

Large industrial batteries, submarine batteries and a few RE battery manufacturers have used air injection for years to stir the electrolyte during charging. Advantages include:
  • Approximately 20% better round trip charge/discharge efficiency
  • Longer battery life due to elimination of positive plate corrosion
  • Less maintenance (reduction of need for equalization, leading to less plate erosion)
Battery manufacturers that include aeration tubes include TAB Batteries (European RE Mfrs of the TOPzS tubular plate batteries with air tube option) and Exide (on some of their industrial batteries). Seems to that RE battery manufacturers should get on this as for mere pennies (cost of a bit of plastic tubing) their batteries could gain a real competitive advantage.

A couple of interesting articles on studies of the advantages of agitated electrolytes in flooded cell lead acid batteries:

http://www.battcon.com/PapersFinal2013/11-Larry%20Meisner%20-%20The%20Effects%20of%20Mechanical%20Electrolyte%20Mixing%20VLA%20Cells%20in%20Renewable%20Energy.pdf


[FONT=&quot]http://cecri.csircentral.net/215/1/110-2005.pdf[/FONT]

Anybody using air bubble mixing of their batteries? - Maybe I'll take a drill to the top corner of my old batteries, push some tubing in under the plates and epoxy some tubing in .....

- Graham

Offgrid in cloudy PNW

Full Schneider system with 18 REC 420W panels, 100A-600V controller, XWPro, Insight Home, six Discover AES Rackmount 5kW batteries, Slimline enclosure, Lynk II, AGS, H650,  H2200, H3000, Kubota 4500, Onan 7500.

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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Member "John P" has done that test for us (he works in a test lab and gets to play using other people's money--really cool). From an old post/thread:

    http://forum.solar-electric.com/forum/solar-electric-power-wind-power-balance-of-system/off-grid-solar-battery-systems/16664-when-does-electrolyte-stratification-occur?p=210105#post210105
    This article is behind a pay wall:

    Effects of Electrolyte Stratification on Performances of Flood Lead-Acid Batteries

    Abstract
    The electrolyte stratification in the charge/discharge of lead-acid cells was monitored by a sensor of mml-math-1.gif specific gravity and an in situ electrochemical scan technique was used to measure the current distribution directly on the plates in the rest state. A simulated cell was set up to study the electrochemical behavior of lead-acid batteries with electrolyte stratification. The active mass (AM) in the lower part is discharged in preference to that in the upper part. During recharging, however, the AM in the upper part is more easily charged. The more concentrated the mml-math-2.gif solution, the finer the formed AM becomes. Two mechanisms of sulfation have been proposed. For the batteries often at rest or in the discharge state at very low current, the sulfation occurs in the lower part of the plates, but for the batteries in continual cycles at a high current, it often appears in the upper part.



    And there are other studies:

    Dependence of Lead Acid Battery Performance on Electrolyte ...

    The above appeared to discuss some of the same types of testing that John P did at his work and published here (mixing of electrolyte).

    Anyway--It appears that the electrolyte will [not? -BB] stratify on its own accord... My guess is that the bubbles from charging and even the heat from charging/discharging helps mix the electrolyte (and the discharge heat helps very cold battery performance--mixing cools the plates and reduces cold weather performance)...

    In the end, flooded cell lead acid batteries want discharge from the bottom and recharge at the top--Certainly not ideal. And I would suggest that very light loads and charging currents are not helpful for long battery life.

    -Bill

    PS: Member "John P" tests on pumping air to mix/agitate electrolyte in storage batteries. The setup and test results are in this thread:

    Air pumps for better battery charging

    PPS: I am not sure what I was writing at the time--Either I missed the "not" or I have changed my mind and think charging/cycling causes stratification (when low current/not gassing). -Bill B. 7/10/13

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #3
    Are you asking or selling?
    Sounds great on paper. In real life? In almost all cases a waste or money. But like a religion, there are believers.;
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #4
    Everybody.... BB has already given you the link to the mods I did and the tests and the results.. Simply put.. YOU will have no battery warranty.. And the net result it uses more power to do it than what you gain if you are using solar panels to power the pumpe.. Heavy equipment only does it while engine .is operating.. so no problems getting adequate power.. Large industrial sites are using mains power so again plentyful 24/4 .. solar ?? about 5hrs max a day.. And to get the best result it needs to be done 24/7..
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  • Graham Parkinson
    Graham Parkinson Registered Users Posts: 167 ✭✭✭
    #5
    Thanks for the interesting links BB - Amazing what has already been looked at by John P and others.

    Maybe worth while when batteries are factory equipped with aeration tubes (no effect on warranty).

    Those of us on islands have another free source of 24/7 energy for battery bubbles: Wave Energy.

    Have been looking at ways of creating low pressure air with a wave powered resonant air column (open ended pipe and flapper valves) hanging off our dock - Was originally thinking of this for aerating our septic treatment system but would be equally applicable to battery aeration. Mostly just a for fun research project, but an interesting idea.

    By the way, $6.5 M has been set aside to stimulate designs for Wave Energy Conversion. The WEC up! prize money awards will be administered by the Ricardo Corporation on behalf of the US Energy Department

    Get your ideas in now!

    http://energy.gov/eere/water/articles/wec-energy-department-announces-wave-energy-conversion-prize-administrator

    Cheers, Graham

    Offgrid in cloudy PNW

    Full Schneider system with 18 REC 420W panels, 100A-600V controller, XWPro, Insight Home, six Discover AES Rackmount 5kW batteries, Slimline enclosure, Lynk II, AGS, H650,  H2200, H3000, Kubota 4500, Onan 7500.

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