Improvement in or in connection with the Construction of Dry Voltaic Cells, Accumulators, and Secondary Batteries.
Year: 1898

page_text: Date of Application, 19th Nov., 1898-Accepted, 23rd Dec., 1898
:
Improvement in or in connection with the Construction of Dry
Voltaic Cells, Accumulators, and Secondary Batteries.
I; CLARENCE METCALFE STEAD, of Merrion Street, in the City of Leeds, Elec-
trical Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement; —
:
This invention relates to an improvement in or in connection with the con-
struction of dry voltaic cells, accumulators and dry secondary batteries; and
more particularly with the object of obtaining and preserving a sound or effectual
wet or moist electrical connection between the electrodes of the cell, said con-
nection being due to the retention and continuity of the moisture in and through
the mixture. A further advantage of this invention is, that the labour of making
the cells is kept at a minimum.
For the purpose of the following description, the invention is hereunder first
described with reference to primary cells, in which the cell will be supposed to
consist of a carbon core or rod, surrounded by a mixture of graphite or plumbago
and manganese per-oxide as a depolarising mixture, and an outer zinc cylinder
for the positive electrode. I wish it to be understood, and it will be evident
from the following description, that this invention is not limited to cells of the
above construction.
In connection with dry cells, the exciting mixture often consists of a mixture
of plaster of Paris an aqueous solution of ammonium chloride and some vegetable
material, such as flour; the object of the latter being to absorb and retain the
moisture necessary to keep the cell in working order.
Now I have discovered, that peat moss, owing to its power of absorbing and
retaining large quantities of water, possesses very considerable advantage, but in
the natural state in which I sometimes use it, it forms with the plaster of Paris
a mixture, which is not uniform throughout; in some cases the former and in
other the latter preponderating; and this want of uniformity usually occurs when
it is packed in place by hand, which is necessary when using it in its natural
condition. When this is the case, the moisture is not so efficiently retained, Bo
that the internal resistance is increased, thereby reducing the power or output of
the cell, owing to the peat moss not having an effective surface contact or con-
nection with the zinc cylinder and with the carbon mixture.
'
I have also found, that by subjecting the peat moss to a grinding operation,
sufficient to reduce it to a very fine powder or flour, that not only is it then readily
mixed with plaster of Paris to produce a uniform mixture, but it can also be made
into a cream, sufficiently liquid to be poured into its place in the cell, where it
sets to a moist semi-solid or plastic state; thereby obtaining a very considerable
saving in the labour of making these cells. Also owing to this fine condition of
the peat moss, a larger portion of it can be mixed with the setting materials, so
that the cells can be supplied with a larger amount of the exciting solution, than
is the case where the peat moss is used in its natural state. As an example of

page_text: suitable portions in which the peat moss may be used, I find that a mixture
consisting of 70 per cent. or thereabouts of finely powdered peat moss, 20 per cent.
or thereabouts of plaster of Paris, 10 per cent. or thereabouts of whiting, answer
well for absorbing and retaining the aqueous solution of ammonium chloride or
other exciting agent, and that a cell thus constructed and sealed, will continue
in order for years according to use.
In the case of secondary cells and accumulators, the peat moss is usually
employed used in the finely divided condition without plaster of Paris or other
setting materials in a semi-fluid state, where it can be put in and the excess or
surplus of acid drained off, leaving it in a semi-dry or moist state. It can also
be used, though less advantageously, without setting materials in the case of
primary cells.
In the case of accumulators, the porosity of the moist finely ground peat moss
permits of the ready escape of hydrogen gas; and it retains a sufficiently large
quantity of acid solution, without the risk of spilling, which is of considerable
importance in the case of motor vehicles.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
1. In the construction of dry voltaic cells accumulators and dry secondary
batteries the employment of peat moss substantially as herein set forth.
2. In the construction of so-called dry voltaic cells the use of peat moss in a
finely divided state mixed with plaster of Paris and whiting or other suitable
setting materials to a liquid consistency the mixture being then poured into
place in the partially constructed cell substantially as herein set forth.
3. Dry voltaic cells consisting of an inner carbon core or rod surrounded by a
depolarising mixture within a zine or other metallic cylinder having a liquid
mixture of finely divided peat moss with plaster of Paris and whiting or other
suitable setting material poured into and set in the space between the depolarising
mixture and the zinc or other cylinder with ammonium chloride or other exciting
agent substantially as set forth.
4. In accumulators and dry secondary cells the use of peat moss in a finely
divided state saturated with acid substantially as and for the purpose herein
set forth.
T
L
1000