Method for adapting high voltage cells or batteries for lower volt rated applications

A high voltage cell or battery has its voltage reduced for lower voltage applications by means of volt lowering diodes i.e. p-n junction and resistive elements placed in series with the cells and the appliance to be electrically powered.

This invention relates to high voltage cells and batteries and their 
utilization in lower volt rated applications and more specifically to 
alkaline Zn/MnO.sub.2 cells or batteries being utilized in equipment 
adapted for the lower voltage Zn/Carbon cells or batteries. 
For many years flashlights, lanterns and other portable lighting appliances 
were powered by the ubiquitous Zn/Carbon or leclanche cells or batteries. 
Consequently such lighting equipment was adapted to the voltages obtained 
from such cells or series multiples of such cells. Leclanche cells and 
concomitantly batteries of such cells embodied very rapidly declining 
voltages such as in typical lantern batteries from an initial voltage of 
about 1.55 to about 1.2 volts in less than about 5 hours. Accordingly, 
bulbs utilized in flashlights, lanterns and the like adapted for leclanche 
cell or battery use were rated in comformity with such rapidly achieved 
low voltages. However, alkaline Zn/MnO.sub.2 cells of similar size 
generally require from about four to six times as long to achieve the same 
voltages as the leclanche cells. As a result, the bulbs rated for the 
lower voltages of leclanche cells are exposed to higher voltages for 
longer periods of time when utilized with alkaline cells and the advantage 
of the alkaline cells or batteries of long discharge life is prematurely 
obviated by rapid bulb failure. 
It is an object of the present invention to provide a means for enabling 
the effective use of high voltage cells or batteries in lower voltage 
applications. 
It is a further object of the present invention to provide a means whereby 
specifically an alkaline Zn/MnO.sub.2 cell or battery may be utilized in a 
lighting appliance adapted for leclanche cell or battery use without 
premature failure of the appliance.

Generally the present invention comprises a means for reducing the 
operating voltage of high voltage cells or batteries whereby such cells or 
batteries become compatible with equipment adapted for cells or batteries 
having lower operating voltages. The voltage reduction means of the 
present invention comprises one or more diode or p-n junctions hereinafter 
referred to as "diodes", together with one or more resistive elements 
placed in series with the cell or the cells of the battery and the 
appliance utilizing the cell or battery of cells. The voltage drop 
attainable with the most common diodes of silicon and germanium are 
constant at varying current drains at about 0.7 and 0.3 volts respectively 
with the diodes being serially cumulated to achieve higher desired voltage 
drops. 
Coupled with the voltage drop of the diode or diodes is the voltage drop of 
one or more resistive elements placed in series with the diode or diodes. 
The resistive element may either be a resistor or more preferably 
comprises an intercell connector such as a metal tab having the requisite 
degree of resistivity. The use of a resistive metal tab is preferred since 
it eliminates the need for a component other than those normally utilized 
in a battery. Examples of metals having the requisite degree of 
resistivity, in the size and thickness of metal tabs commonly utilized for 
intercell connection, include the various alloys of nickel and chromium. 
The resistor or resistive element or elements should provide a total 
resistivity in the series connected circuit of between 0.1 to 10 ohms per 
cell. The average voltage drop associated with a preferred (because of its 
utilizable dimensions--with proper resistance characteristics--for 
intercell tab stock) nickel chromium alloy, Trophet C (trademark of W. B. 
Driver Co. for its 60% Ni, 16% Cr and 24% Fe alloy) in 2.25 mil (0.056 mm) 
thick ribbon is about 0.25 volt with a resistance of 2.27 ohms/ft (0.7 
ohms/meter). Thus, for example, in a four cell battery having two 
intercell connectors of about 1.5" (3.8 cm) each, the Trophet C metal 
alloy tabs provide a resistance of about 0.5 ohm or 0.125 ohm per cell. 
Utilization of a resistor or resistive element of higher resistance to 
provide a greater voltage drop in lieu of the diode is undesirable for 
several reasons. Increasing the resistance of metal tab stock results in a 
more fragile interconnector increasingly subject to breakage. Furthermore, 
since the resistive element is primarily a reducer of current rather than 
of voltage a higher resistance would unduly reduce utilizable cell 
capacity with excessive heat generation. Furthermore, in lantern 
applications wherein a flasher is included therewith a resistor in the 
circuitry thereof would cause undesirable flashing in the latern segment 
because of the continual current changes in the current requirements of 
the flasher segment. Diodes, on the other hand, have been found to 
maintain a constant voltage drop regardless of current drain. However, 
because diodes such as those of silicon and germanium are current 
sensitive under cell short circuit conditions they must be at least 
minimally protected by the current reducing resistor particularly when 
utilized with high current drain lantern or flashlight cells or batteries. 
Though diodes have been utilized in the past as battery protective devices 
they have been placed in parallel circuit with the individual cells for 
the purpose of preventing cell reversal. In such parallel electrical 
configuration however, any voltage drop attained was minimal without the 
effect of the series connected diode or diodes of the present invention. 
It is further noted that the voltage dropping diode of the present 
invention may be utilized with both a single cell or series of cells in a 
battery. However, since cell reversal is a problem unique to two or more 
cells connected in a series (one cell may drive a defective cell into 
reversal) to form a battery, diodes have not generally been utilized for 
the protection of individual cells. 
In lanterns adapted for use with the leclanche batteries the most common 
bulb types are the PR-13 and PR-15 with rated voltages of 4.8 and rated 
lives of 15 and 30 hours respectively. Exposure of such bulbs to voltages 
above 4.8 volts for extended periods of time severely reduces their 
lifetimes. It is however noted that bulb failure is not always inevitable 
and is dependent upon the specific type of filament composition and 
construction. However, because cells and batteries are not restricted to 
utilization with the more resistant bulbs, application of the present 
invention is required for greater consumer acceptance in all applications. 
FIG. 1 depicts a battery 10 of four series connected cells 11 a-d in a 
typical lantern battery configuration. Each of the cells 11 a-d is wrapped 
with a heat shrink insulative material 17 to prevent intercell short 
circuiting. Resistive nickel chromium alloy tab 12 electrically 
interconnects cells 11a and 11c and silicon diode 14 electrically 
interconnects cells 11b and 11d. The diode is enwrapped at its ends with 
folded tab stock 15 whereby it is welded to cells 11b and 11d for positive 
electrical connection. Cells 11c and 11d are electrically interconnected 
at their other ends (not shown) with a resistive nickel chromium tab such 
as tab 12. The remaining terminals of cells 11a and 11b (not shown) 
provide the external terminal connection to an electrical device to be 
powered therewith such as a lantern. FIG. 2 schematically depicts the 
series circuit of the cells with the voltage reduction means of the 
present invention. In the configuration shown wherein the cells are "F" 
cells (1.3" D (3.3 cm).times.3.4" H (8.6 cm)) the resistive tabs in the 
preferred embodiment of 2.25 mil (0.056 mm) thick Tophet C nickel chromium 
alloy are each 1.5" (3.8 cm) with acumulative resistance of 0.5 ohms. The 
voltage drop for the silicon diode is about 0.7 and that of the resistive 
elements is about 0.25 volts for a total voltage drop of nearly one volt 
for the four cell battery. As depicted in FIG. 3 discharge curves A and B 
are of a leclanche battery and a Zn/MnO.sub.2 battery respectively and 
FIG. C is that of the Zn/MnO.sub.2 battery with the voltage reduction 
means of the present invention as shown in FIG. 1. Batteries A, B and C 
were discharged with a PR-15 bulb at room temperature. It should be noted 
that several bulbs were blown after about 3 hours of discharge of 
Zn/MnO.sub.2 batteries without the voltage reduction means until a bulb 
was able to last through the entire discharge. Though there is a capacity 
penalty with the utilization of the voltage reduction means it is only 
about 10-15%. This is more than compensated for by the nearly sixfold 
lifetime of the battery as compared to the leclanche battery of the same 
size and the possibility of having a battery of high capacity but with an 
inoperable device. 
It is understood that various modifications may be made in the cells and 
batteries to be used in the present invention such as the use of 
transistors with diode p-n junctions and constant voltage drops and the 
invention is not limited to the specifics illustrated above except as 
defined in the following claims.