A light rechargeable battery includes a rechargeable cell having an elongated, tubular case characterized by a longitudinal axis, and a pair of terminals extending therefrom. Two or more thin-film solar cells fabricated on a flexible substrate and interconnected in a series circuit between the terminals are circumferentially positioned around the rechargeable cell on the exterior of the case. A blocking diode is connected in the series circuit with the solar cells. The solar cells are coupled to the terminals by bus bars. A transparent shrink wrap cover secures the solar cells to the case of the rechargeable cell.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to rechargeable batteries. In 
particular, the present invention is a light-rechargeable battery. 
2. Description of the Prior Art 
Electrically rechargeable batteries are well known and in widespread use. 
Batteries of this type must be recharged using a charging unit which is 
typically powered by an AC line source or car battery. A major drawback of 
these rechargeable batteries, as well as that of non-rechargeable 
batteries, is that their output falls to unusable levels abruptly, without 
forewarning, and often when the user is away from a charger or source of 
power. 
Light-rechargeable batteries are also known and disclosed, for example, in 
the Curiel U.S. Pat. No. 4,563,727. This battery includes an arrangement 
of planar solar cells which are electrically connected in series and 
spaced with respect to one another about a longitudinal axis of the 
battery. Since the solar cells face outward on only one side of the 
battery, it must be properly oriented with respect to a source of light to 
be efficiently recharged. The structure of this battery is also relatively 
complicated. 
Japanese Patent Publication No. 60-158565 discloses a battery having a 
plurality of solar cell elements mounted to its exterior. The solar cells 
are spaced both circumferentially and longitudinally about the battery. A 
battery having an amorphous silicon solar cell fabricated on a stainless 
steel substrate which is wrapped around the battery is shown in Japanese 
Patent Publication No. 57-75535. 
It is evident that there is a continuing need for improved 
light-rechargeable batteries. A light-rechargeable battery with charging 
characteristics which are relatively independent of the physical 
orientation of the battery with respect to a source of radiant energy is 
desired. To be commercially viable, the battery must be relatively 
inexpensive to manufacture. 
SUMMARY OF THE INVENTION 
A light-rechargeable battery in accordance with the present invention 
includes a tubular rechargeable cell having a pair of terminals extending 
therefrom. Two or more solar cell units are interconnected in a series 
circuit between the terminals. Each solar cell unit extends substantially 
around a circumference of the cell. The solar cell units are secured to 
the rechargeable cell by fastener means. The light-rechargeable battery is 
inexpensive to manufacture, and can be efficiently recharged relatively 
independent of its orientation with respect to a light source. This 
arrangement will have a low overall series resistance, resulting in high 
overall efficiency. 
In preferred embodiments the battery includes a blocking diode connected in 
the series circuit. Bus bars couple the solar cell units to the terminals. 
The solar cell units include thin-film solar cells fabricated on a 
flexible substrate. A transparent shrink wrap cover is used to secure the 
solar cell units to the rechargeable cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A light-rechargeable battery 10 in accordance with the present invention is 
illustrated generally in FIGS. 1 and 2. Rechargeable battery 10 includes 
an elongated member, such as rechargeable cell 12, which has a 
longitudinal axis 14. In the embodiment shown, rechargeable cell 12 is 
cylindrical or circular in cross-section. Metal and/or chemical storage 
media 16 of cell 12 is sealed within a case formed by top wall 18, tubular 
side wall 20, and bottom wall 22. A relatively positive terminal or anode 
24 extends from top wall 18 of cell 12, while a relatively negative 
terminal or cathode 26 extends from bottom wall 22. Two or more 
photovoltaic (PV) strips or solar cell units such as 28A, 28B, and 28C are 
fastened about the exterior circumference of case side wall 20, and 
interconnected in a series circuit by interconnect zones 27A and 27B. 
Photocurrent generated by solar cell units 28A-28C is coupled to 
rechargeable cell 12 by bus bars 29 and 31. Solar cell units 28A-28C are 
secured to cell 12 by a fastener such as transparent heat shrink wrapper 
30. 
Rechargeable cell 12 can be any known rechargeable or storage-type battery 
including nickel-cadmium (Ni-Cd), nickel-iron (Ni-Fe), silver-zinc 
(Ag-Zn), silver-cadmium (Ag-Cd), lead-acid or similar rechargeable 
devices. Trickle-charging or charge-maintaining means in combination with 
primary or "non-rechargeable" batteries (so called because standard 
alkaline-manganese-zinc or zinc-carbon batteries are not considered to be 
economically rechargeable) can also be used. Top wall 18, side wall 20 and 
bottom wall 22 can be formed of metal or any other material which securely 
encases but does not adversely affect media 16. Batteries of the type 
described above are well known and commercially available. 
FIG. 3 is a schematic diagram illustrating the electrical interconnections 
between the various elements of rechargeable battery 10. As shown, solar 
cell units 28A-28C are interconnected in a series circuit with one another 
by means of interconnect zones 27A and 27B. The series interconnection of 
solar cell units 28A-28C is also interconnected in a series circuit with a 
blocking diode 32 (not shown in FIGS. 1 and 2). The series interconnection 
of solar cell units 28A-28C and diode 32 is connected across anode 24 and 
cathode 26 of rechargeable cell 12. 
Solar cell units 28A-28C and diode 32 can be of any known type having 
suitable electrical characteristics. In one embodiment, solar cell units 
28A-28C and diode 32 are thin-film hydrogenated amorphous silicon (a-Si:H) 
devices fabricated on a common flexible polyimide substrate. Devices of 
this polyimide type are described in a copending application entitled 
"METHOD FOR MANUFACTURING AN AMORPHOUS SILICON THIN-FILM SOLAR CELL AND 
SCHOTTKY BARRIER DIODE ON A COMMON SUBSTRATE", which is assigned to the 
same assignee as the present invention. Discrete blocking diodes 32 can 
also be used, as can single or multi-junction solar cells having tandem or 
stacked structures. The sum of the voltage potentials generated by solar 
cell units 28A-28C must exceed the potential of rechargeable cell 12 by 
the threshold voltage of blocking diode 32 in order for rechargeable 
battery 10 to accept charge. 
In addition to being interconnected in a series circuit, solar cell units 
28A-28C are physically positioned on battery 10 in such a manner that 
their adjacent edges are non-parallel to axis 14. In the embodiment shown, 
cells 28A-28C are positioned on side wall 20 in such a manner that their 
edges are generally perpendicular to axis 14, and extend around a 
circumference of cell 12. An imaginary line parallel to axis 14 and 
positioned across the exterior surface of rechargeable battery 10 will 
therefore intersect at least a portion of each solar cell unit 28A-28C. In 
other words, solar cell units 28A-28C are physically positioned in series 
along the length of cell 12. Although each solar cell unit 28A-28C is a 
unitary device in the illustrated embodiment, each unit could also be 
formed from a plurality of discrete solar cells positioned about the 
circumference of cell 12 and interconnected in a parallel circuit. 
Bus bars 29 and 31 can be fabricated of any desired electrically conductive 
material such as metal or conductive transfer adhesive (CTA) films. In one 
embodiment, 3M SCOTCHLINK Brand electrical connector tape is used for bus 
bars 29 and 31. 
Tubular wrapper 30 can be positioned around solar cell units 28A-28C, and 
"heat shrunk" to secure the solar cells in place on case side wall 20. 
Commercially available heat shrinkable polymer materials can be used for 
this purpose. Wrapper 30 must of course be generally transparent to 
visible light to permit propagation of radiation to solar cell units 
28A-28C. Small amounts of printing or other labeling on wrapper 30 can 
also be included without significantly detracting from the amount of light 
received by solar cell units 28A-28C. Pressure sensitive or other 
adhesives can also be used to fasten solar cell units 28A-28C to cell 12. 
By way of example, a standard D size Ni-Cd rechargeable cell 12 having a 
typical charge capacity of 1.2 amp-hour (AH) can be charged to full 
capacity from a totally drained condition by applying a 50 mA DC charging 
current for thirty-two hours. The minimum required charging voltage using 
a crystalline silicon blocking diode (0.6 volt threshold) is about 2.0 
volts. Using an a-Si:H blocking diode, a minimum voltage of about 2.2 
volts is necessary. This can be accomplished with four, series-connected, 
ten square centimeter, three percent efficient a-Si solar cells under AMl 
(100 mW/cm.sup.2) illumination. Ten percent efficient solar cells can 
provide the same result under AMl illumination with solar cells of three 
square centimeters. 
When charged, battery 10 can be used in a conventional manner to power any 
electrical device. Current from cell 12 is prevented from flowing through 
solar cell units 28A-28C by blocking diode 32. Blocking diode 32 thereby 
prevents cell 12 from being discharged when battery 10 is placed in the 
dark. When battery 10 is removed from the device it is powering and 
exposed to natural or artificial light, or if the device on which battery 
10 is mounted permits the propagation of light (e.g. a flashlight having a 
clear case), photocurrent generated by solar cell units 28A-28C will 
charge cell 12. Due to the orientation of solar cell units 28A-28C, 
radiation direct from the light source will impinge upon at least a 
portion of each solar cell unit 28A-28C, unless its longitudinal axis is 
oriented directly toward the source. All solar cell units 28A-28C will 
therefore receive more or less a similar distribution of radiant energy, 
and generate about the same amount of photocurrent. As a result, each 
solar cell unit 28A-28C will present a similar low value of electrical 
resistance in the circuit shown in FIG. 3, resulting in an increased 
charging efficiency over prior art arrangements. Detrimental effects 
associated with non-uniform light distribution upon solar cells, which can 
result when position-sensitive rechargeable batteries are not properly 
oriented with respect to the source of radiation, are thereby alleviated. 
Light rechargeable batteries such as 10 have significant utility as "always 
charged" batteries. They can be used in conjunction with batteries of any 
voltage, including battery packs/modules in flashlights, or in posts or 
other devices housing electronic transmitters or sensors. Posts or other 
elongated members used in conjunction with rechargeable cells and having 
solar cell units mounted thereon in the manner described above will also 
have the advantageous features described herein. Rechargeable batteries 10 
will therefore remain fully charged on store shelves, dashboards, aboard 
ships, window shelves, and in transparent battery compartments on portable 
appliances or field electronic equipment. Rechargeable battery 10 is 
further enhanced by the fact that its charging behavior is relatively 
insensitive to its orientation relative to the source of light. Light 
rechargeable batteries 10 are charged-maintained at no cost to the user. 
Even "non-chargeable" batteries can therefore be made economically 
rechargeable. No additional equipment such as a charger unit is required. 
Any number of batteries 10 can therefore be charged simultaneously. Solar 
cell units 28A-28C of the thin-film type described are very attractive and 
durable. Solar cell units 28A-28C of the thin-film variety are relatively 
inexpensive and can be easily wrapped around the circumference of case 
side wall 20. Battery 10 can therefore be manufactured at low additional 
cost beyond that of cell 12 itself. 
Although the present invention has been described with reference to 
preferred embodiments, those skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention.