Best alternatives for alum?

[Georg Seema]

Greetings!

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: http://endless-sphere.com/forums/vie...p?f=39&t=52800

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?

Thanks!

George

[Georg Seema]

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...

[BobZilla]

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.

[Georg Seema]

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.

[aln]

George,
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

[guyzzemf]

Georg
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
guy

[Georg Seema]

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

http://www.hho4free.com/bedini_alkaline_battery.htm

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....

[aln]

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

[Georg Seema]

Aln

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?

[Georg Seema]

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.

[guyzzemf]

georg
if you discharge below 10.5 v you will hurt batt.

https://www.youtube.com/watch?v=K4__eH9-MXk

http://batterysecrets.com/

ell. A 12 volt lead acid battery has 6 cells and must not be discharged below 10.5 volts (6 x 1.75 = 10.5). If these batteries are discharged below this, they will most likely be damaged.
http://www.clairmont.com/tech_tips/batteries_care.html

[aln]

Guy,
George's battery is no longer a typical lead acid battery. My alum batteries flatline between 7-10 volts. How big of a battery did you convert Geroge? 2*45=90 watts/12v= 7.5 amps of discharge (that is a heavy load) for 1.5 hours then it drops off. rule of thumb, c20 discharge rate is ah/20, much nicer to battery. Al

[Georg Seema]

aln
My battery is (or was ) 52AH. I recharged it yesterday and it works fine... I Did the same discharge test and again it lasted about 2 hours till the voltage droped to 9V. Then I removed the bulbs and put it on the charger. Interestingly my smart charger (when in discharge mode) discharges 12V lead acid to 9V which is under the "safe level"? I will do the graph again today then we can compare the results.

52Ah/c20 = 2.6H. My battery lasts 2 hours... I think it is not so bad considering it is 10 years old (it was just sitting in garage for 3 years with acid in it when last summer I started using it) and converted with epsom salt not alum. Maybe if it desulfates it will get little bit better.

[aln]

George,
52 amp hours/c20= 2.6 amps for 20 hours. That is the safe discharge rate. You are pulling 7.5 amps for 2 hours. 7.5*2= actual capacity, 14Ah. You will get more amps out of your battery if you decrease the draw. Your "smart charger" is smart on the part of the battery companies. They will sell you a new one in a couple years if you discharge a regular lead acid to 9v repeatedly. Aln

[Georg Seema]

I have been testing higher epsom salt concentration solutions with smaller lead acid battery for few days. Every time that I have increased amount of epsom salt in the mix, the more amp-hours I am being able to pull out of it.

Update:
I did just finish filling the car battery with much higher concentration mix. The old (four days old) fluid that came out of it was totally black/greyish. And I had to fill up and dump out water from the battery over 30 times to get it cleaned out. A lot of lead powder came out of it...
This time I will be charging it up slowly and I will be making new discharge graph in few days.