Electricity: battery or capacitor charging or discharging – Cell or battery charger structure
Reexamination Certificate
2000-08-18
2002-03-12
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Cell or battery charger structure
C429S065000
Reexamination Certificate
active
06356051
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the improvement of a battery pack incorporating a PTC device therein. In particular, the present invention relates to a battery pack and a PTC device incorporated in such battery pack wherein a plurality of unit cells placed side by side in parallel are connected in series with the PTC device.
BACKGROUND ART
PTC devices are incorporated in battery packs as protection devices. The PTC device connected in series with unit cells will, when an overcurrent flows through the cells or a temperature of the cells rises, protect the cells by increasing its electrical resistance rapidly so that the cell current is shut off or reduced to a virtually zero value.
A battery pack having a PTC device connected to unit cells in series is described for example in Japanese Patent Laid-open Publication (Tokkai Hei) No. 9-63553. As shown in
FIG. 1
, the battery pack described in this publication has the PTC device P connected between two unit cells
1
which are positioned linearly. The PTC device P has a top surface connected to an end electrode
1
A of one unit cell
1
and a bottom surface connected to an end electrode
1
A of the other unit cell. This structure is suitable for incorporating the PTC device in the battery pack where the unit cells are positioned linearly. However, such a PTC device cannot connect cells in a desirable condition in a battery pack where the unit cells are placed side by side in parallel.
A battery pack incorporating a PTC device and having unit cells placed in parallel is described in Japanese Utility Model Laid-open Publications (Jikkai Hei) Nos. 2-69440 and 6-38157.
FIG. 2
shows an exploded perspective view of the battery pack described in the former publication.
FIGS. 3 and 4
show the PTC device incorporated in the battery pack and the battery pack incorporating the PTC device as described in the latter publication.
The battery pack shown in
FIG. 2
incorporates a PTC device P having a first electrode
3
and a second electrode
4
connected to a bottom surface and a top surface respectively of a rectangular PTC layer
2
. The first electrode
3
and the second electrode
4
protrude from the both sides of the PTC layer
2
and are connected to the end electrodes
1
A of the unit cells
1
. In this structure, the battery pack has the PTC layer
2
between the adjacent electrodes
1
A of the cells
1
placed in parallel.
The PTC device P shown in
FIG. 3
has a PTC layer
2
which is disk-shaped having an external size which is generally the same as the diameter of the unit cell and which is formed to allow the convex electrode of the cell to be inserted. The PTC layer
2
in this form can be placed around the convex electrode. A plate-shaped first electrode
3
is connected to the bottom surface of the PTC layer
2
. In order to insert the convex electrode, the first electrode
3
has a convex-shaped center portion which is inserted into the center hole
2
A of the PTC layer
2
. A second. electrode
4
having a semi-spherical section along the PTC layer
2
and a protruding lead is connected to the top surface of the PTC layer
2
. The first electrode
3
is connected to the convex electrode, and the second electrode
4
is, as can be seen in
FIG. 4
, connected to the end electrode
1
A of the adjoining unit cell
1
.
The PTC devices shown in
FIGS. 2 and 3
are convenient for incorporating in battery packs which have a plurality of unit cells
1
placed in parallel. In particular, the PTC device shown in
FIG. 3
is characterized in that it can be placed around the convex electrode so that it hardly protrudes from the unit cell.
However, the battery packs described in those publications are limited by the area of the PTC layer so that it is difficult to make it larger. In the PTC device P shown in
FIG. 2
, the first electrode
3
and the second electrode
4
cannot be connected to the end electrodes
1
A of the unit cells
1
if the PTC layer
2
is made larger. This PTC device P cannot be made wider than the spacing between the end electrodes
1
A of the adjoining unit cells
1
.
Also, in the PTC device P shown in
FIGS. 3 and 4
, the outer size of the PTC layer
2
cannot be made greater than the thickness of the unit cell
1
. If it is made greater, it would protrude from the cell
1
so that the size of the battery pack is locally increased. Further, the PTC layer
2
in this form has the center hole
2
B, which decreases the substantive area of the PTC layer
2
that can be used.
Since the PTC device is used while connected in series with respect to the unit cells, it is important that the internal resistance of the PTC device is small under normal conditions. This is because the PTC device consumes power in proportion to the product of the internal resistance of the PTC layer and the load current squared. Further, in battery packs used for large current applications, the current through the PTC device also increases. The PTC device can be designed to withstand the large currents by increasing the area of the PTC layer. In order to decrease the internal resistance and increase the large current, it is important to make the area of the PTC layer in the PTC device larger. However, battery packs heretofore had a shortcoming in that it was difficult to achieve this.
DISCLOSURE OF THE INVENTION
The present invention has been developed for the purpose of solving this shortcoming. An important purpose of the present invention is to provide a battery pack and a PTC device incorporated in such battery pack which could be used safely under large current loads by increasing the area and decreasing the internal resistance of the PTC layer.
The battery pack according to claim
1
of the present invention has a plurality of unit cells
1
placed side by side in parallel and a PTC device P to protect the cells
1
from overcurrents. The PTC device P has a first electrode
3
and a second electrode
4
attached to both surfaces of the PTC layer
2
. The PTC device P is connected in series to the unit cells
1
by connecting the first electrode
3
and the second electrode
4
to the end electrodes
1
A of the two unit cells
1
whose end electrodes
1
A are positioned on the same or almost the same plane. It is intended that the term “almost” is used to include the concept of “substantially the same plane”.
The outer shape of the PTC layer
2
is formed to cover almost the entirety of the end surfaces of the two cells
1
to which the first electrode
3
and the second electrode
4
are connected. Further, the PTC layer
2
has through holes
2
B positioned correspondingly to positions of the end electrodes
1
A of the cells
1
.
The first electrode
3
and the second electrode
4
attached to both surfaces of the PTC layer
2
are formed into an outer shape that is almost the same as the outer shape of the PTC layer
2
; and the first electrode
3
and the second electrode
4
are connected to the end electrodes
1
A of the unit cells
1
through their portions which are located correspondingly to the through holes
2
B of the PTC layer
2
.
The PTC device according to claim
5
of the present invention protects the unit cells
1
from the overcurrents by connecting the first electrode
3
and the second electrode
4
which are attached to the both surfaces of the PTC layer
2
to the end electrodes
1
A of a plurality of the cells
1
placed side by side in parallel.
The outer shape of the PTC layer
2
is formed to cover almost the entirety of the end surfaces of the two cells
1
to which the first electrode
3
and the second electrode
4
are connected. Further, the PTC layer has the through holes
2
B positioned against the end electrodes
1
A of the cells
1
.
The first electrode
3
and the second electrode
4
connected to both surfaces of the PTC layer
2
are formed into almost the same outer shape as the outer shape of the PTC layer
2
; and the first electrode
3
and the second electrode
4
are connected to the end electrodes
1
A of the unit cells
1
at points where the through holes
2
B of the P
Hasunuma Takashi
Osaki Kazuo
Watanabe Atsushi
Yoshinari Fumiyoshi
Luk Lawrence
Tyco Electronics Raychem K.K.
Wong Peter S.
LandOfFree
Battery pack and PTC element incorporated in the battery pack does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Battery pack and PTC element incorporated in the battery pack, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Battery pack and PTC element incorporated in the battery pack will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2821318