Desulfation: too good to be true?

Aluminiumni
Aluminiumni Registered Users Posts: 5 ✭
in Off Grid Solar & Battery Systems #1
I was curious about desulfation; how far can we go? Why not totally focus on maximally minimizing plate corrosion.

Is the problem that once sulfation happens, desulfation only provides temporary relief and it keeps getting worse? Are there other deterioration processes involved in cycling? Is cycling even in the 20-40% SOC range still going to give plate deterioration close to plate deterioration in cycling in the 50-100% SOC range?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Desulfation: too good to be true?

    Batteries are complex mix of chemistry, electrical, and mechanical.

    There are so many factors that go into "battery performance" that it is very hard to generalize. But getting specific is almost of no use either (telling you to run the battery from 50% to 80% SOC for 3-10 days, then recharge to >90%.... Sounds easy--But there are not many products out there that will automate this process. And not all batteries will do well cycled down to 50% and still have long life.

    Roughly, if you keep the battery charge above ~75% SOC, sulfation is less of a problem. However if you keep the battery >90%-100% SOC most of the time, then you will get positive plate corrosion (Oxygen gas forms on the positive plate and oxidizes the batteries positive grid).

    Add that batteries are spec'ed to operate at 77F / 25C, and for every 10C over 25C, the battery life is but in 1/2 (conversely, for every 10C below 25C, battery storage live is ~2x).

    In the end, there are things that we recommend to do to ensure that the batteries are not "murdered"...

    Monitor electrolyte levels. Never let plates be exposed to air. Use distilled (or other very low mineral content water like filtered rain water).

    Do not over charge... Do not Deficit charge (basically too much load with too little recharging capacity). Monitor/log specific gravity, cell/battery voltages. Watch for trends and if you see anything out of the ordinary (when compared with other cells/batteries) figure out what is going one.

    Poor electrical connections, taking a battery to "dead", shorted/open cells, etc. all can destroy a battery bank in hours/days.

    Everyone pretty much kills their first battery bank. So, getting a less expensive "training bank" can be a good idea. It both allows you to learn and make a mistake that does not take you to the poor house--And it allows you to figure out if you have a the "right size" bank for your loads and available charging energy (solar panels, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Aluminiumni
    Aluminiumni Registered Users Posts: 5 ✭
    #3
    Re: Desulfation: too good to be true?

    Thank you for the detailed info Bill,

    Btw are you Bill Blake from fieldlines.com? I partly read a Ni-Fe battery thread, remember "fast talking salesman". :D

    What's the deal with desulphators? I just read Battery Maintenance - De Sulfation. KnowledgeSponge said, "I know they make real ones that have lots more output." If some people claim that a real desulphator can always desulphate to at least 50% capacity, then why not run an experiment to see how pure 20-40% cycling goes with it.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Desulfation: too good to be true?

    Nope, not me... I post here almost exclusively (takes enough of my time). In years past, I used to post at Candle Power Forums as "BB".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Desulfation: too good to be true?

    ftr bill blake is a member here.
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