Reduction of Battery Voltage and Deterioration of Capacity
(1) Reduction of battery voltage and deterioration of capacity through contact with antistatic
conductive materials
Incidents have been reported where terminal-mounted batteries for memory backup or coin-type lithium batteries have
come into contact with antistatic conductive materials, thus forming external discharge circuits and leading to voltage drops
or capacity deterioration.
In manufacturing plants using ICs, LSI and other semiconductor components, thoroughgoing antistatic measures are taken.
Various protective materials are used to prevent static: most of them have special compounds of carbon, aluminum foil and
other metals and are therefore conductive. These protective materials are used, for example, in the form of packaging bags,
trays, mats, sheets, films, corrugated boards and resin cases.
A protective material may have a resistance ranging from 10
3
to 10
6
Ω/cm,
for instance. This means that if the (+) and (-)
terminals of a battery come into contact with this material, a current ranging from several milliamperes to several microamperes
will flow and the battery will discharge, causing voltage drop and capacity deterioration.
A terminal-mounted battery was inserted into a
conductive mat. The battery charge was exhausted
in several days.
-
+
A battery was placed directly
on a rubber sheet spread over
a worktable. The (+) and (-)
terminals were in contact with
the sheet and the battery
charge was exhausted.
Exclusive grounding line
Conductive
rubber sheet
Conductive mat
Conductive rubber sheet
Battery-mounted PC boards were inadvertently
brought into contact with spacers and a conductive
rubber sheet. The battery
Spacer
charge was exhausted.
When batteries are to be used near protective materials,
take every possible care to ensure that the (+) and (-)
terminals of the batteries or PC boards, etc. on which
batteries are mounted do not touch these protective
materials directly.
Rubber sheet
A battery-mounted PC board was inadvertently
brought into contact with a conductive resin case.
The battery charge was exhausted.
Conductive resin case
LITHIUM HANDBOOK
AUGUST 2005
This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications
are subject to modification without notice. Contact Panasonic for the latest information.
Preventing Quality Problems
(2) Reduction of battery voltage and deterioration of capacity through contact between batteries
Incidents have been reported where terminal-mounted batteries for memory backup or coin-type lithium batteries have
come into contact each other, thus forming discharge circuits (shorted state) and leading to voltage drops or capacity
deterioration. Observe the following precautions.
1. Remove the batteries from the tray one at a time.
If the tray is turned upside down, the batteries will come into contact with each other, forming discharge circuits.
2. Do not place batteries randomly in a parts box or other container.
Discharge circuits will be formed by multiple batteries coming into contact, causing the batteries to discharge and
drain.
Recommended procedures
*Utilize the tray lid in taking out batteries
Prohibited procedures
*Do not throw batteries randomly into a parts box
by turning over trays containing batteries.
Intermediate package
(200 batteries):
20 pieces
✕
10 trays
Tray containing batteries
Trays containing batteries
Lid tray (tray with no hole)
Batteries
Parts box
Discharge circuits
Trays containing batteries
Batteries being exhausted
Lid tray
protruding part
Battery being exhausted
Battery being exhausted
*Contact of batteries with each other forms discharge
circuits, thus the batteries are drained.
*Lay a tray lid flat and place a tray containing batteries on
top of it: batteries are pushed up by protrusions of the lid
tray so that they can be easily picked up with fingers.
LITHIUM HANDBOOK
AUGUST 2005
This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications
are subject to modification without notice. Contact Panasonic for the latest information.
Preventing Quality Problems
Memory Erasure Problems
Coin-type lithium batteries are often used as the power
supplies for memory backup in various equipment. However
problems with the erasure of valuable data in the memory
due to improper contact between the batteries and
equipment can occur.
Fig. 1: soldering
1. When batteries are to be used continuously for a
prolonged period
●
Select tab terminal-mounted batteries, and solder
the tabs to the battery connection terminals of the
equipment. (See Fig. 1)
●
When batteries need to be replaced, use a battery
holder (see Fig. 2) or battery with lead wire
connectors (see Fig. 3).
2. When batteries need to be replaced in the short
term, select batteries with no terminals or lead wire
connectors.
●
Use of Y-shaped terminals (2-point contact) for
both the (+) and (-) poles as the shape of the
connection terminals in the equipment helps to
achieve a more stable contact. (See Fig. 4)
The contact pressure of the contacts should be no
less than 2 to 10N (approx. 200 to 1000 gf). (See
Fig. 5)
●
To prevent momentary contact failure of several
milliseconds in the circuit, the use of a tantalum
capacitor, etc. with a capacitance of several
microfarads is effective. (See Fig. 6)
●
For the connection terminals of the equipment,
use iron or stainless steel with nickel plating at the
very least. Gold-plating is more suitable when the
contact resistance must be reduced.
Note:
Do not touch batteries with bare hands because
perspiration (salt), body oil etc. will increase the
surface resistance which may lead to defective
contact.
Fig. 2
Fig. 3
Fig. 4
Fig. 5: load
2~10N
Fig. 6
IC
LITHIUM HANDBOOK
AUGUST 2005
This information is generally descriptive only and is not intended to make or imply any representation, guarantee or warranty with respect to any cells and batteries. Cell and battery designs/specifications
are subject to modification without notice. Contact Panasonic for the latest information.
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