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Dynamic Lead-Acid Battery

Less size and weight by pumping moving acid to the cells
  [vote for,

Use smaller cells, closer to each other, and have the water (acid) pumped over to the cells. Much smaller cells would be needed. Also, unused cells (for an application like electric cars, where not all cells are being used at once) could be stored even more compactly.
pashute, Jun 09 2010


       What matters in a secondary cell is the available reactive surface area of the electrodes, not the amount of electrolyte, which acts only as a transfer medium for ions.   

       Sorry, bad electrochemistry.
8th of 7, Jun 09 2010

       so... why's the acid turn to water then ?
FlyingToaster, Jun 10 2010

       The acid is about 6 molar; higher concentrations start releasing hydrogen gas as the sulfur reacts with the lead in another undesireable reaction. Probably if your sulfuric acid content has dropped its due to this other reaction taking place.   

       Lead-acids are really poor for an electric vehicle application. Known technology, but bad current signature as the battery overpotential increases and the voltage drops off. Bad life-cycling behavior as well. Once they're cooked, they're cooked.   

       Stirring or pumping the electrolyte could have some effect because the ion charge density across the gap decreases at what's called the 'stagnant layer,' with which adds to overall battery resistance.   

       Cell size is determined by efficient packaging space, heat issues, and voltage and amperage requirements.
RayfordSteele, Jun 10 2010

       // Stirring or pumping the electrolyte could have some effect //   

       Only a problem with gel electrolytes. In batteries with liquid electrolyte, in vehicles, the movement of the vehicle causes enough "sloshing" to agitate the liquid and minimise this effect.   

       The exception is a "cold start" of a statioanry vehicle, although with prolonged cranking, the plates heat up and convection effects move the liquid around.
8th of 7, Jun 10 2010

       a. How does the heat affect the output. If it would be pumped through and cooled, would that assist with the output.   

       b. Having a stream go through the lead - would be considered a larger surface, as Rayford explained, because of freeing the "stagnant layer". That was my line of thinking. So not all that bad electrochemistry.
pashute, Jun 10 2010

       It wouldn't be that much. Surface area is the largest factor by far.   

       Temperature plays an important role; in the equation it shows up in at least two terms in affecting the battery resistance.   

       All hybrid battery packs, be they Lithium or NiMH rely on passive or active cooling systems to keep them as close to ambient as practical. A runaway heat event is both a power drain and a fire hazard. And with Lithium, you just gotta let it burn.
RayfordSteele, Jun 10 2010

       I'm not quite clear what you're trying to accomplish here. While one could theoretically store cleaned and dried electrodes without space between them, in most batteries the electrodes are already very close together (kept apart by thin spacers). I suppose in some rare cases it might be practical to carry around spare electrodes rather than spare batteries (one the assumption that failed electrodes would be removed and discarded) but if one wants to have 'N' batteries in use at once, one will need N sets of electrodes, plus N sets of spacers, plus N units of acid. I don't know how one would store those things separately in a fashion that would be more compact than simply storing N batteries.   

       Also note that acid is an electrical conductor, and it's imperative that there be no electrical connection between the acid in different cells. Any system to automatically adjust battery fluid levels is most likely going to require a separate reservoir for each battery, or else connect batteries to/from a common reservoir by moving pipes (as opposed to switching valves).
supercat, Jun 10 2010


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