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Author Topic: Large Salt water battery ideas and questions  (Read 56494 times)

profitis

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Re: Large Salt water battery ideas and questions
« Reply #15 on: August 12, 2013, 07:53:46 PM »
what you want to do is make your cathode more oxygen-catalytic to depolarize H2 gas as much as possible so etched copper would probably serve best.you want to increase surface area of the copper by soaking or splashing some hydrochloric acid on exposure to air for a few minutes before thorough rinsing.you want to etch it to roughen surface area. Copper undergoes a double reaction in seawater exposed to air under these circumstances..Cu + Cl- + O +2H+ = CuCl(precipitates on the copper)+H2O.Then CuCl acts as depolarizer 2CuCl + Zn= ZnCl2 +2Cu.copper is regenerated,acting as cyclic catalyst for O2 consumption

Mungo

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Re: Large Salt water battery ideas and questions
« Reply #16 on: August 12, 2013, 09:36:23 PM »
what you want to do is make your cathode more oxygen-catalytic to depolarize H2 gas as much as possible so etched copper would probably serve best.
Thanks Pofitis.  Would scoring or abrading the copper work as well, or would etching be preferable?

profitis

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Re: Large Salt water battery ideas and questions
« Reply #17 on: August 13, 2013, 12:00:43 AM »
etching defnitly better @mungo.much more surface area.use dilute nitric,or conc hydrochloric acids(swimpool acid).test it smallscale first.

Mungo

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Re: Large Salt water battery ideas and questions
« Reply #18 on: August 13, 2013, 01:37:17 AM »
Ill try that.  Any feedback on the airstone idea?

profitis

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Re: Large Salt water battery ideas and questions
« Reply #19 on: August 13, 2013, 06:42:56 PM »
aha,the airstone idea is nt necessary if you have sufficient porosity.  porous carbon will work but you,re going to have to order carbon slices with emphasis on porousity which is available in different degrees from industrials. you might want to try making your own lead-acid cells simply by passing current between 2 lead plates in sulfuric acid solution.this will give a more power and smoother voltage but you will have to recharge when flat.

Mungo

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Re: Large Salt water battery ideas and questions
« Reply #20 on: August 13, 2013, 08:37:05 PM »
I find the porosity thing interesting.  Certainly etching the cathode would help, but going with an industrially produced cathode which had to be ordered or utilizing sulphuric acid as an electrolyte rather defeats the purpose of the experiment, which was to create a big dumb battery out of commonly available materials with low toxicity.  My other thought regarding the airstone was that it would keep the electrolyte oxygenated, and perhaps stop the voltage die off I experienced in the small model.  Thoughts?  Does the anode need to be etched as well (aluminum seems to be the top contender here, though zincs used to protect crab traps are widely available in the Chesapeake.)

profitis

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Re: Large Salt water battery ideas and questions
« Reply #21 on: August 14, 2013, 07:26:15 PM »
definitely @mungo.an etching of the aluminum or zinc with hydrochloric acid beforehand will shoot up the power density.a shaking of the air electrode will be energy consuming but it will help yes but we want to try avoid putting in energy to gain efficiency.if you situate the cathode half-submerged in the seawater it may help absorbtion of air from the atmosphere and self-discharge of the clinging H2 bubbles.try putting the copper plate side-longways half-submerged.try a copper plate that is 2wice as big as the zinc plate for surface area.try folding up a giant copper plate into squigglies(like a roofing) to cram huge area into small space,half-submerged.

profitis

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Re: Large Salt water battery ideas and questions
« Reply #22 on: August 14, 2013, 07:32:38 PM »
try pressing your electrodes between sponge-soaked salt water @mungo.make sure that the sponge is not overly soaked,just a tiny bit seawater will do as you want it to be an almost 'dry cell'.this should alow maximum air access via pores.try newspaper,try fabric,fibreglass as your saltwater sponge.

Mungo

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Re: Large Salt water battery ideas and questions
« Reply #23 on: August 14, 2013, 09:06:17 PM »
try pressing your electrodes between sponge-soaked salt water @mungo.make sure that the sponge is not overly soaked,just a tiny bit seawater will do as you want it to be an almost 'dry cell'.this should alow maximum air access via pores.try newspaper,try fabric,fibreglass as your saltwater sponge.

could capillary action from a well of electrolyte be used to keep the sponge medium damp, or would that be too much?

profitis

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Re: Large Salt water battery ideas and questions
« Reply #24 on: August 14, 2013, 10:36:37 PM »
it certainly could.you just have to work out the right sponge.it will be obviously wetter on the base but at least the top will be exposed to more air.the correct way to do this is to actualy have the zinc completely submerged under seawater and just the copper standing aloft against the sponge.we want minimum air exposure to anode and maximum air on cathode.

profitis

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Re: Large Salt water battery ideas and questions
« Reply #25 on: August 14, 2013, 10:44:24 PM »
you could also use a cramped up bundle of copper wire half-submerged in seawater or pressed against sponge for maximum air exposure.make sure that the wire bundle is all electricaly connected in a straight line before bundling and make sure that the insulator coating is all burned off the wire completely beforehand.

Mungo

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Re: Large Salt water battery ideas and questions
« Reply #26 on: August 14, 2013, 11:37:57 PM »
how about a bundle of copper pipe, riveted together with copper rivets and etched, half submerged, as you said, and twice the size of the aluminum anode? :) this is fun, and instructive :D



profitis

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Re: Large Salt water battery ideas and questions
« Reply #27 on: August 15, 2013, 12:10:25 AM »
now a plan is coming 2gether yes indeed.try find pipes that are pencil-thin and bundle them.we want maximum copper/air/electrolyte exposure.pipes slightly pressed onto a sponge or towel will allow air to creep at an angle.

profitis

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Re: Large Salt water battery ideas and questions
« Reply #28 on: August 15, 2013, 12:28:31 AM »
try doing a spot-test using bundled wire half-submerged and tell us if you get improved result @mungo.im realy curious if the theory will match practicality.use normal appliance cord wire,throw it into a fire to charcolize its rubber coat and simply bash off the charcoal pieces,they will fall off like glass,scrap dealers do this all the time

SeaMonkey

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Re: Large Salt water battery ideas and questions
« Reply #29 on: August 15, 2013, 07:36:31 AM »
Experimenting with chemical voltaic cells such
as the Saltwater Battery can be great fun and
an enormous learning experience;  but when
one realizes how little energy they're capable
of producing for all the work that goes into them
it is sadly disappointing.

These types of Voltaic Cells are great for emergency
use to energize low powered devices for a short
time, but when more substantial power is required
the ubiquitous lead-acid battery with a suitable
charging/desulfation device (solar or wind powered
or both) is hard to beat.