Re: [EVDL] Press release on Firefly "Oasis" battery
Bill Dube wrote:
> I think it was the "Horizion" battery that used composite
Correct. The Horizon used fiberglass reinforced lead grids, instead of
solid lead grids. Lead is very soft and mechanically weak; the idea was
to improve the strength of the grids. Therefore less lead could be used
for structural support, increasing the energy density of the battery.
The Horizon had another trick; it was a true bipolar lead-acid battery.
Lead-acid chemistry is unique in that both plates are made of the same
metal (lead). One plate is converting lead into lead sulfate; the other
converts lead oxide into lead sulfate. The Horizon used the plates
themselves as the separator between cells. One side is the positive
plate of one cell, and the other side is the negative of the adjacent
cell. This further reduced the need for lead as a current-carrying
conductor, further increasing the energy density.
> They had serious issues with cycle life. Could be this latest spin on
> the old idea will have similar problems. Maybe not.
The drawback was that any tiny leaks either through or around the edges
of these special plates became a short between cells. Horizons had big
problems with self-discharge and balancing issues because of this, which
seriously reduced their life.
> Regardless, it will be tough to beat the Li-Ion specs with any sort
> of lead-acid. 2.17 volts per cell versus 3.3 (or 3.8) volts per cell
> is tough to overcome.
The extra voltage is nice; but what we'd really like is higher energy
density (more amphours per pound). Lead would be great if it wasn't so
You could theoretically improve lead-acid batteries about 2:1 if you
could somehow eliminate all the lead used for mechanical support and
current carrying conductors. The problem is that few materials will
survive in the sulfuric acid electrolyte.
> Many folks on this list are quite jaded from seeing a continuous
> parade of "pre-announced" technologies fail to work as advertised.
> Many of us now have a "Show me" attitude after all these years.
Yep; that's me! But I'm a skeptic, not a cynic. I think it's possible to
improve batteries; but it's very difficult.
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
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