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Thread: Best alternatives for alum?

  1. #1

    Best alternatives for alum?


    I'm 16 year old who likes to build things and experiment with electronics and other stuff. I like to fish and last summer I built a brushless trolling motor by my self:

    I had some old car batteries to power it, but after a year I can feel, that they are starting to lose their power. I think that they are good candidates for Alum conversion, but it is quite hard to find that stuff in Europe. + it is quite expensive. I have found a local chemical store that sells the pure stuff for around 20-30 euros per KG.

    There is so much info about alum conversions on the internet, but very little about alternatives for it, so I thought I might ask for some help on this forum.

    1. I have sourced Epsom salts locally for quite cheap. How would that compare as alternative to Alum?
    2. There is a big debate about what alum to use (ammonium aluminum sulfate / potassium aluminum sulfate: As I understand both can be used. But what would yield better results?
    3. Are there any other chemicals that can improve battery performance?
    4. Mixing ratio? I have seen people making over saturated solutions... Are there any benefits to that?
    5. Other good knowledge/tips about conversions?


    Last edited by Georg Seema; 06-12-2014 at 01:47 PM.

  2. #2
    Yesterday I started converting one of my lead batteries with magnesium sulfate (Epsom salt). I'll post here when it is done and how it turned out...

  3. #3
    Hi George,

    This may not be what you want to hear but the problem you have with your batteries is not the chemical. Your plates are sulphated and changing the chemical will not help, you need to desulphte them by whatever method you prefer.

  4. #4
    yeah I know that... But anyway the plates looked Ok and I have replaced the acid with 1:10 epsom salt:distilled water mix. The acid that came out of it was clean and there wasn't any big lead pieces in it. The battery is now on charger.

  5. #5
    Hi there, welcome to the thread. I only have experience with aluminum ammonium sulfate so I can only speak to that as far as ratios and what to expect. From my experience, however, I do not believe super saturation is the key to getting more amp hours out of a well-used-somewhat-sulfated-battery. By saying "super saturation" I mean heating up your distilled water to absorb as much chemical as possible. What I believe I ran into was the solution cools in battery and during discharge and charge cycles is becomes difficult for the sulfate ions of an already sulfated battery to move into the "super saturated" solution. Just something to ponder during your experiments. Enjoy, Al

  6. #6
    for what its worth you my not see sulfation at first if the batt loses capacity its getting sulfated
    i dont know if a converted batt will desulfate
    Last edited by guyzzemf; 06-13-2014 at 06:52 PM.

  7. #7
    I don't know either, but that is what I am trying to find out...

    After the conversion it should have more capacity and now I should be able to discharge it more deeply without hurting it. This is what I have read....

  8. #8
    A converted battery will desulfate some if the solution has room for the sulfate ions. Bad cells will still be bad cells, unless you can remove deposits of pbso4 from between the plates whe you are rinsing the plates off for conversion. Aln

  9. #9

    There weren't any bad cells in the battery and the solution I made has more than enough room for sulfate ions. Epsom salt solubility is 71g/100 mL @ (20 °C). But my solution is 10g/100mL.
    Should I pour in fresh solution after few charge/discharge cycles? MgSo4 is much more soluble than alum. Would higher consentration make any difference next time?
    Last edited by Georg Seema; 06-15-2014 at 01:03 AM.

  10. #10
    Here is first discharge curve. I hope the battery capacity will increase after few cycles. For discharging I used two 45W halogen car light bulbs connected in parallel. I let it discharge over night and in the morning it had around 0.7V. For the voltage graph I used my smart rc charger.


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